Thermal Stability Of Coatings Research Articles

Oxidation resistance and thermal stability of (MoZrHfTaNb)-Si-B coatings deposited by HIPIMS method with different Ar pressure

The influence of argon pressure on the structure, mechanical characteristics, oxidation resistance, and thermal stability of (MoTaNbZrHf)-Si-B coatings deposited by HIPIMS method using a composite target based on high-entropy (MoZrHfTaNb)Si2 silicide and (MoZrHfTaNb)B2 boride was studied. Coatings deposited at Ar pressure of 0.1–0.2 and 1.3–2.2 Pa had a dense, defect-free structure. Increasing the Ar pressure to 37–42 Pa led to the formation of a coating with a columnar structure, while, according to X-ray diffraction and transmission electron microscopy, all coatings were amorphous. Increasing the Ar pressure from 0.1 to 0.2 to 37–42 Pa led to a magnifying the growth rate of coatings in 2.5 times. All coatings were characterized by a similar hardness of 14–15 GPa. The elastic modulus and elastic recovery decreased from 196 to 178 GPa and from 40 to 34 % when the argon pressure increased from 0.1 to 0.2 to 37–42 Pa, respectively. The coatings successfully resisted oxidation at temperatures of 1100 °C and 1300 °C. The protective properties of the coatings are due to the formation of a dense oxide film based on a-Si:B:O amorphous phase with crystallites of the m-HfO2, m-ZrO2, m-Nb2O3, o-Ta2O5, t-ZrSiO4 and t-HfSiO4 phases. Heating in a TEM column showed that the coating deposited at an Ar pressure of 0.1–0.2 Pa crystallizes immediately upon reaching a temperature of 700 °C with the release of predominantly the h-MoSi2 phase. Crystallization of the coating obtained at an Ar pressure of 37–42 Pa also occurs at 700 °C, but only during long-term exposure and is accompanied by the precipitation of the h-Ta5Si3 and t-Nb5Si3 phases. Thus, it has been shown that by increasing the gas flow rate, the productivity of sputtering in the HIPIMS mode can be increased without a significant loss in hardness, oxidation resistance and thermal stability of coatings.

Production of AlN/CNT reinforced PVA nanofibers as a thermal conductive net for thermal interface applications

The amount of heat generated by electronic components is increasing daily, in line with their growing power and performance. Consequently, there is a heightened demand for thermal interface materials for enhanced cooling of electronics. This study employs a novel approach to fabricate a nano composite thermal interface material on copper substrates to address this challenge. The thermal interface coatings, consisting of carbon nanotubes (CNT) and aluminum nitride (AlN)-reinforced polyvinyl alcohol (PVA) nanofibers with and without an epoxy resin matrix, are fabricated using the electrospinning technique. The findings demonstrate the successful fabrication of a 2.5 µm-thick CNT/AlN-PVA nanocomposite fiber mat coating with an average fiber diameter of 318 nm onto copper substrates. Scanning electron microscope (SEM) images revealed that the AlN particles and CNTs penetrated the fibers. The successful incorporation of AlN particles into PVA fibers was also verified by the Fourier-transform infrared spectroscopy (FT-IR) spectrum of CNT/AlN-PVA nanofibers. No major weight loss was observed in the thermogravimetric (TG) analysis curves up to 200 °C, indicating the thermal stability of coatings. The thermal diffusivity of the copper substrate coated with the CNT/AlN-PVA nanocomposite fiber mat was measured at 36.6 mm2/s. Moreover, the developed CNT/AlN-PVA nanocomposite fiber mat was also applied on top of the fire-retardant epoxy resin-coated copper substrate, which is conventionally used in electronic devices to provide electrical insulation. SEM images revealed that the existence of an epoxy layer on top of copper substrates did not alter the fiber formation during the electrospinning process, and an approximately 2.5 µm-thick CNT/AlN-PVA nanofiber mat was effectively embedded in the epoxy layer after a 1-hour electrospinning process. The thermal diffusivity of the resulting epoxy matrix CNT/AlN-PVA nanofiber reinforced nanocomposite coating is determined to be 7.792 mm2/s, which is 30-fold higher compared to the thermal diffusivity of neat epoxy resin coatings (0.254 mm2/s).

Microstructure, mechanical properties and thermal stability of Cr/WC nano-multilayered coating synthesized by ion beam sputtering

Cr/WC nano-multilayered coatings with fixed period ratio (Cr:WC=1:2) were synthesized by using ion beam sputtering method. The microstructure, mechanical properties and the thermal stability of coatings were investigated by X-ray diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy and nanoindentation. Well-defined laminar amorphous microstructure and uniform monolayers, which consists of amorphous WC1-x and Cr, can be found in the as-deposited nano-multilayered coatings with series modulation period. Although the hardness of Cr/WC nano-multilayered coating increases with the increasing of modulation period, it is still lower than the value predicted by Hill model. Almost all the toughness of Cr/WC nano-multilayered coatings are lower than that of monolayer Cr coating, however, they are higher than that of monolayer WC coating, indicating that the addition of Cr and nano-multilayered architecture can improve the toughness of monolayer WC coating. Both microstructure and mechanical properties of Cr/WC nano-multilayered coatings were stable when the vacuum heat treatment temperature was lower than 400 °C. As the heat treatment temperature was 600 °C, some nanocrystalline W2C, W and WC1-x were enclosed in the amorphous WC sublayer which is beneficial to its hardness enhancement while it is harmful to its toughness. As the heat treatment temperature was 800 °C, the nano-multilayered structure was destroyed completely and its mechanical properties were seriously degraded.

Preparation and properties of ceramic-based conductive coatings

Ceramic-based conductive coatings were prepared by sol–gel method with artificial graphite (CGM) as conductive fillers and methyltrimethoxysilane (MTMS) and silica sol as dispersion medias. The graphene (Gr) and carbon black (CB) were added to improve the properties of the resultant coatings. The results showed that the electrical conductivity and thermal stability of coatings were improved by the addition of Gr and the electrical conductivity of coatings was further improved by the addition of CB for decreasing the pores of coatings. When the amount of CGM was 15.0 wt% with adding 1.0 wt% Gr and 0.5 wt% CB in the coating, the resistivity of obtained coating reduced to 1.46 Ω·cm and its adhesion increased to 3911.62 mN. The prepared coating presented excellent electrical conductivity and adhesion properties, which was much better than the coating prepared without adding Gr and CB.

Influences of film forming materials on the performance of graphene fire resistive coating

Four types of film forming materials were used in graphene fire resistive coatings to investigate the fire protection, smoke suppression, water resistance and physical properties by corresponding tests. Firstly, weather resistance of emulsions was tested and evaluated. Additionally, distribution state of graphene in the emulsion was conducted by precipitation method test, particle size distribution test and contact angle test, respectively. The impact test and adhesion test were carried out to evaluate physical properties of coatings. TGA was used to studied thermal stability of coatings and SEM was carried out to analyze the microstructure of carbon layers. The results demonstrated graphene could well dispersed in vac-veova emulsion and the corresponding graphene fire resistive coating performed best in fire protection, smoke suppression, thermal stability and water resistance. Although silicone acrylic emulsion exhibited poor weather resistance, graphene fire resistive coating contained silicone acrylic emulsion performed better in the adhesion test and impact test due to the silicon element.

Nitrided Silicon-Carbon Coatings Structure and Properties

The paper considers structural and physicomechanical properties of silicon-carbon coatings deposited from a gaseous medium in doping with nitrogen ions. The analysis of the coatings by X-ray photoelectron spectroscopy shows that nitriding of silicon-carbon coatings promotes the formation of silicon nitride and compounds such as CNx and SixOyNz. A 1.5–2-fold increase in the content of sp2 -hybridized carbon and silicon carbide atoms is found to prevent silicon oxidation. Thermal annealing of the resulting silicon-carbon coatings increases the content of the graphite phase and silicon oxide.It is shown that doping of the working gaswith nitrogen (Ar57% + N43%) leads to the formation of a more finely dispersed structure as compared to that when using argon only. During thermal annealing in air, the decreased carbon concentration and increased oxygen concentration can be observed due to silicon and carbon oxidation followed by desorption of carbon and oxygen compounds. In addition, annealing leads to nitrogen desorption from the coating. Nitriding of silicon-carbon coatings increases the dispersion of their structure, and heat-resistant compounds CNх, Si3N4 improve heat resistance and thermal stability of coatings, and increase microhardness and friction coefficient in friction units.

Thermal Stability of CrWN Glass Molding Coatings after Vacuum Annealing

CrWN glass molding coatings were deposited by plasma enhanced magnetron sputtering (PEMS). The microstructure and thermal stability of these coatings were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscope, atomic force microscope and nanoindentation tests. The as-deposited coating exhibited an aggravated lattice expansion resulting in a constant hardness enhancement. The vacuum annealing induced surface coarsening and the spinodal decomposition of the coating accompanied by the formation of nm-sized c-CrN, c-W2N, and h-WN domains. The annealed coating with low W content had mainly a face-centered cubic (f.c.c) matrix, strain fields caused by lattice mismatch caused hardness enhancement. Following an increase in W content, the annealed coating showed a mixed face-centered cubic (f.c.c) and hexagonal close-packed (h.c.p) matrix. The large volume fraction of h-WN phases seriously weakened the coating strengthening effect and caused an obvious drop in hardness.

Thermal stability and optical properties of low emissivity multilayer coatings for energy-saving applications

In this study, the deposition and characteristics of Si- and Ti-series multilayer coatings with respective glass/Si3N4/NiCr/Ag/NiCr/Si3N4 and glass/TiO2/ZnSnO3/ZnO/Ag/NiCrOx/ZnSnO3/Si3N4 structures were investigated. Experimental analyses were performed, and the optical performance and thermal stability of the coatings were assessed. The as-deposited Si- and the Ti-series samples exhibited optimal shading coefficient of 0.49 and 0.57, respectively. Thermal annealing in air was performed to analyze the thermal stability and oxidation resistance of the samples. The Si- and Ti-series samples prevented the failure of low-emissivity properties at 700 and 600 °C, respectively. In addition to high transparency, the Si-series samples exhibited improved low-emissivity properties, reduced light pollution, and superior thermal stability compared to the Ti-series samples. The use of Si3N4 and NiCr layers effectively prevented the oxidation and cracking of the Ag layer upon heat treatment. This study presents the characteristics of Si- and Ti-series samples for energy-saving building applications.

Castor oil based UV-cured coatings using thiol-ene click reaction for thermal degradation with flame retardance

In this paper, castor oil based UV-cured coatings are prepared via thiol-ene click reaction by varying molar content of a self-synthesized phosphorus-containing flame retardant (DA), a self-synthesized castor oil based-mercaptan (COSH) and 1,3,5-triethylene-1,3,5-trimethylcyclotriazane (TTC), which is used for the study of synergistic effectivities for flame retardant component, photopolymerization kinetics, and thermal degradation. The results demonstrate the synergistic effectivities between DA and TTC via effective quantification of Lewin’s parameter (ES). Under the molar ratio of DA, TTC and COSH of 3:3:5, the thermal stability of coatings is significantly better than others and the char yield can reach 14.54% at 800 °C under air condition despite achieving better flame retardant properties, and the conversion of thiol and vinyl groups can reach 70% or more. Further, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) tests show that polyphosphoric acid formed through the decomposition of DA can promote SiO and SiC bond into compact and stable char layer timely to protect wooden substrates and delay burning, which indicates the synergistic fire retardant property of P and Si in the condensed phase. Moreover, there are nonflammable gases (CO2 and SO2) released from the coatings to dilute oxygen concentration during thermal degradation by the analysis of thermogravimetry/infrared spectroscopy (TG-FTIR) tests, which also leads to the generation of porous char layer on the surface of wooden substrates. Besides, the oxygen can be also consumed by the phosphorus-containing compounds generated by DA simultaneously, which shows the synergistic fire retardant property of S and P in the gas phase.

Flexible and thermally stable superhydrophobic surface with excellent anti-corrosion behavior

Superhydrophobic films with excellent flexibility, mechanical robust and thermally stable properties have been fabricated through a facile one-step spray-coating process based on bisphenol A based benzoxazine (BA-a), polyurethane (PU) prepolymer, and mesoporous SiO2 (SBA-15). The curing mechanism between BA-a and PU prepolymer morphologies, water contact angles and thermal stability of coatings were characterized and discussed. In addition, the corrosion behavior of the superhydrophobic coatings on the tin plate was characterized by the polarization curve and electrochemical impedance spectroscopy. The coatings made by different weight ratios of BA-a to PU can maintain a contact angle higher than 150°; meanwhile, the coatings had a micro-nano structure with a Tg more than 221 °C. The coatings can be bent by the finger which illustrates their excellent flexible properties. Furthermore, friction coefficient of coatings can reach 1.70. The electrochemical corrosion test results indicated that the superhydrophobic coatings possessed excellent corrosion resistance (Icorr can reach 8.90 × 10−5 A cm−2 with certain ratio), which could have a potential at harsh environment.

Thermal stability and optical properties of single-layer nano-composite TiN/TiC-Ni/Mo solar-selective-absorbing coatings by laser cladding

Currently, the most important challenge for solar energy photo-thermal utilization is the thermal stability of solar absorber coatings at high temperature. The new one-layer nano-composite TiN/TiC-based cermet coatings were designed and fabricated with laser-cladding method in the air. The result indicated the laser cladding could be used to obtain 30 wt.%, TiN-30 wt.%, TiC-20 wt.%, and Ni-20 wt.% Mo cermet coatings with the desired optical properties. In particular, an absorptance (α) of ~ 80.1% and a thermal emissivity (e) of ~ 2% at 300 K were calculated when the weight rate of nano-particles/micro-particles is 1:1. In addition, the thermal stability of the coating was outstanding after heat treatment at 650 °C for 6 h. The absorptance and emissivity of cermet coating were, respectively, 80.8% and 1.9% at 650 °C. The results indicated that nano-composite TiN/TiC-Ni/Mo cermets are suitable for spectrally selective materials. Moreover, the laser cladding was found to be an improved and novel preparation method in the field of solar-selective-absorbing coatings.

Thermal stability and Weatherability of Single-Layer Micron Scale Cermets Solar Selective Absorbing Coatings by Laser Cladding

The thermal stability of solar absorber coatings at high temperature is the most important challenge for solar energy photo-thermal utilization. A new one layer micrometer-size TiC/TiN-based cermet coating was designed and fabricated with laser cladding method in air. The result indicated the laser cladding could be used to obtain a TiC/TiN-Ni/Mo cermet coating with the desired optical properties. An absorptance (α) of ∼84% and a thermal emissivity (ɛ) of ∼5% at 300 K were calculated. Furthermore, the thermal stability of the coating was outstanding after heat-treatment. The absorptance and emissivity of the TiC/TiN-based cermet coating were respectively 82% and 4.1% at 650°C. The results indicated that TiC/TiN-Ni/Mo cermets are suitable for spectrally selective materials. Furthermore, the cermet coating also possesses excellent weatherability based on the test of the corrosion resistance. The results indicated that TiC/TiN-Ni/Mo cermets are suitable for spectrally selective materials. Moreover, the laser cladding was found to be an improved and novel preparation technology in the field of solar selective absorbing coatings.

Structure, Mechanical Properties, and Oxidation Resistance of MoSi2, MoSiB, and MoSiB/SiBC Coatings

Single-layer MoSi2, MoSiB, and multilayer MoSiB/SiBC coatings are fabricated by magnetron sputtering. Coating structures are investigated using X-ray diffraction, a scanning electron microscopy, and glow-discharge optical emission spectroscopy. Mechanical properties of coatings are determined by nanoindentation. The thermal stability of coatings is studied in a temperature range of 600–1200°C and oxidation resistance is studied upon heating to 1500°C. It is established that single-layer MoSiB coatings possess a hardness of 27 GPa, elasticity modulus of 390 GPa, and elastic recovery of 48%. They can also resist oxidation up to 1500°C inclusively, which is caused by the formation of the SiO2-based protective film on their surface. The MoSi2 coatings can have hardness comparable to the hardness of MoSiB coatings, but they are somewhat worse than them in regards to oxidation resistance. Multilayer MoSiB/SiBC coatings have hardness 23–27 GPa and oxidation resistance restricted by 1500°C, but they herewith have higher elastoplastic properties when compared with MoSiB.

Thermal stability of germanium-carbon coatings prepared by a RF plasma enhanced chemical vapor deposition method

In this work, germanium-carbon coatings were deposited on ZnS substrates by RF plasma enhanced chemical vapor deposition (RF-PECVD) using GeH4 and CH4 as precursors. Thermal stability of coatings were investigated by annealing treatment of samples at different temperatures (200 °C, 300 °C, 400 °C and 500 °C for 3 min , an air atmosphere). Then, the samples were characterized by fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy and field emission scanning electron microscopy (FESEM), methods. With annealing samples at 200 °C and 300 °C, the optical transmittance was increased by 3% in the wavelength region between 3 and 15 µm. There was no remarkable change in transmittance with annealing samples at 400 °C, except for a slight increase in transmittance at the wavelength region between 8 and 9 µm and a slight decrease at the wavelength region between 11 and 12 µm. However, as annealing temperature (Ta) was further increased to 500 °C, the coating was partly peeled off from the ZnS substrate, leading to a sharp decrease in the transmittance of coatings in the wavelength range of 8–12 µm. Annealed coatings at the temperatures of 200, 300 and 400 °C exhibited a structure free of pores. However, as Ta was further increased to 500 °C, the coatings were disintegrated.

Thermal stability of Ni-B/La2O3 coatings by electro-brush plating technique

The metastable materials have attracted the attention of researchers due to their promising physicochemical properties, but the thermal stability limits their practical application. In this paper, Ni-B/La2O3 amorphous/nanocrystalline composite coatings were prepared on AISI 1045 steel substrate by electro-brush plating technique. The surface morphology, component and the phase structure of coatings were observed by Scanning Electron Microscope (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and X-Ray Diffraction (XRD), respectively. The coatings were further analyzed by Transmission Electron Microscope (TEM). Then the thermal stability of coatings with different content of La2O3 was also analyzed under different annealing temperature. It was found that the coating had a unique microstructure consisting of amorphous and nanocrystalline structures. The addition of La2O3 does improve the thermal stability of metastable Ni-B coatings when the annealing temperature is over 355°C. In addition, the thermal stability of the amorphous/nanocrystalline coatings depends on the percentage of amorphous phase and grain sizes.

Thermal stability of specialty optical fiber coatings

Thermal stability of coatings used on specialty optical fibers is assessed via thermogravimetry (TG). The coating lifetimes are evaluated by analyzing dynamic TG curves and assuming a particular level of mass loss as a failure criterion. The studied coating systems include single and dual acrylate, fluorinated acrylate, epoxy, epoxy acrylate, silicone, silicone acrylate, silsesquioxane acrylate and polyimide materials. Processing the data by Arrhenius and Eyring equations indicates that a kinetic compensation effect (KCE) is observed for the decomposition processes, with distinct parameters for different classes of the coatings. Two aspects of the KCE are considered: (1) decomposition within several series of similar compounds in air and (2) decomposition of the same classes in different environments. An attempt is made to use the KCE to predict the lifetimes of the coatings at elevated temperatures.

Solid-state dewetting of continuous thin platinum coatings

Thermal stability of coatings is of crucial importance for reliability of electronic devices operating at high temperature. Thus, we investigated the Cr–Pt system where a thin platinum coating of 0.1μm was deposited on chromium substrate and annealed at 1000°C for 8h. The scanning electron microscope (SEM) showed that a continuous and uniformly deposited Pt coating experienced the formation of “islands” after annealing. The grain-boundary grooving, dewetting and agglomeration were the main mechanisms of degradation of thermally annealed coatings. Results by μ-PIXE (particle-induced X-ray emission) and transmission electron microscope (TEM) showed the presence of Cr3Pt phase in “islands” and the coating thickness was approximately 0.5μm. The surrounding regions were left uncovered due to coating agglomeration at the expense of initially deposited coating.

Знепрозорені нефриттовані поливи для фаянсу та низькотемпературного фарфору

The study results of the oxide composition influence on the glaze properties with temperature formation 1150-1200 ° C are presented. The mathematical dependence of coating gloss, whiteness, thermal stability of coatings on the content of glass-forming, modifying and mufflers components are fitted. The composition of unfritted opaque glazes is developed and the properties and structure and phase composition characteristics of coatings, obtained from using them are defined.

Renewable source-based polyurethane coatings by using monoglycerides of vegetable oils and its modification by nano TiO2

Purpose – The primary purpose of this work is to prepare the renewable source-based polyurethanes coatings which can be used to substitute petroleum-based materials. In the secondary purpose, the paper included improvement in the properties of said PU coatings using modified nano TiO2 for industrial PU coatings. Design/methodology/approach – The authors have synthesised low molecular weight polyols (monoglycerides) based on vegetable oils such as castor, linseed, coconut, mustard, sunflower and rice bran oils. These monoglycerides were successfully utilised in the preparation of polyurethane coatings. In order to improve the performance of these coatings, modified nano TiO2 was incorporated into them. The particle size of TiO2 was determined by transmission electron microscopy. Coatings prepared were characterised for their properties such as gloss, scratch resistance, impact resistance, flexibility, cross cut adhesion and chemical resistance. The thermal stability of coatings was also studied by thermo gravimetric analyzer. Findings – The polyurethane coatings prepared from six monoglycerides of different oils with polymeric diphenyl methane diisocyanate showed good chemical resistance and thermal stability. Coating properties like impact resistance, flexibility and adhesion were excellent for all of the prepared samples of PU coatings. PU coatings with excellent hardness up to 5B were found with the modification of nano TiO2 by silane coupling agent. The authors successfully prepared the renewable source-based (monoglycerides of oil) PU coatings. Practical implications – Practically the authors are able to convert renewable source that is vegetable oils into polyurethane coatings which may have strong potential to be used as industrial surface coating. The properties of the PU coatings were evaluated before and after the incorporation of different concentration of surface-modified nano TiO2 which revealed that the presence of 1 percent nano TiO2 showed significant enhancement in coating properties. Originality/value – The beauty of this work includes synthesis of polyurethanes coatings from renewable source material (monoglycerides of vegetable oils) to substitute petroleum-based materials. The incorporation of silane-modified TiO2 nanoparticles in renewable source-based PU coatings is another originality of the work. This article is also representing comparative study of various vegetable oils on PU coatings.

Phase stability, mechanical properties and thermal stability of Y alloyed Ti–Al–N coatings

The increasing demand for Ti1−xAlxN protective coatings, especially when applied on cutting and milling tools, trigger further studies to enhance their wear performance at high-temperature conditions. To obtain requirements such as high oxidation and corrosion resistance and simultaneously high hardness and elasticity, the formation of quaternary alloys with 4d–transition metals such as yttrium (Y) is a promising approach. In order to study the impact of varying Al and Y content on the industrially preferred cubic structure of Ti1−xAlxN, several Ti1−x−yAlxYyN coatings were deposited using a plasma-assisted reactive magnetron sputtering process. Decreasing Y and Al content favour the formation of the single phase cubic structure. The thermal stability of coatings with single-phase cubic structure was carried out by annealing experiments in vacuum and ambient atmosphere. An increase in hardness of about 10% can be assigned to age-hardening effects which result in its hardness maximum of ≈32.4GPa for Ta=1200°C for Ti0.51Al0.47Y0.02N. The formation of wurtzite structured AlN can be observed for annealing at temperatures above 1100°C. Oxidation experiments (20h at ≈850°C) result in the formation of the typically layered oxide scale (Al2O3 and Ti-rich oxides) on top of the Ti1−x−yAlxYyN coating. For Ti0.51Al0.47Y0.02N, the consumed nitride layer thickness is with ≈20% of the ~3.5-μm film thickness, the minimum of the coatings investigated. In contrast to this, Y free coatings are fully oxidised after 20h annealing in ambient atmosphere at ≈850°C.