Coating Materials Research Articles

(Ba0.5Sr0.5)(Ti0.25Zr0.25Hf0.25Sn0.25)O3: A novel thermal barrier material with low thermal conductivity and excellent resistance to CMAS corrosion

High entropy ceramics are considered as promising materials for thermal barrier coatings due to phonon scattering caused by lattice distortion. In this study, perovskite high-entropy ceramics (Ba0.5Sr0.5)(Ti0.25Zr0.25Hf0.25Sn0.25)O3 (BSTZHS) were successfully prepared by dramatically increasing the conformational entropy of ceramics with complex crystal structures. The results showed that the sample exhibits a single-phase perovskite crystal structure with a dense surface, each element of the sample was uniformly distributed. Moreover, the thermal conductivity of (Ba0.5Sr0.5)(Ti0.25Zr0.25Hf0.25Sn0.25)O3 decreased significantly compared to SrZrO3 and BaZrO3 (the minimum thermal conductivity is 1.37 W/(m·K) at 273–1273 K). This study also identified descriptors for predicting the decrease in thermal conductivity of perovskite high-entropy ceramics. As well, the samples not only exhibit outstanding mechanical properties (Young’s modulus E = 255.7 ± 8.6 GPa、flexural strength Fb = 142.1 ± 4.8 MPa), but also good resistance to CMAS corrosion. Various results support that (Ba0.5Sr0.5)(Ti0.25Zr0.25Hf0.25Sn0.25)O3 is potential to be used for thermal barrier coatings.

Correction: Coating material selection for bulk metal forming dies: a MEREC-integrated approach with multiple MCDM methods

Correction: Coating material selection for bulk metal forming dies: a MEREC-integrated approach with multiple MCDM methods

Novel Approach for the Preparation of a Highly Hydrophobic Coating Material Exhibiting Self-Healing Properties.

A concept to prepare a highly hydrophobic composite with self-healing properties has been designed and verified. The new material is based on a composite of a crystalline hydrophobic fluoro wax, synthesized from montan waxes and perfluoroethylene alcohols, combined with spherical silica nanoparticles equipped with a hydrophobic shell. Highly repellent layers were prepared using this combination of a hydrophobic crystalline wax and silica nanoparticles. The novel aspect of our concept was to prepare a ladder-like structure of the hydrophobic shell allowing the inclusion of a certain share of wax molecules. Wax molecules trapped in the hydrophobic structure during mixing are hindered from crystallizing; therefore, these molecules maintain a higher mobility compared to crystallized molecules. When a thin layer of the composite material is mechanically damaged, the mobile wax molecules can migrate and heal the defects to a certain extent. The general preparation of the composite is described and XRD analysis demonstrated that a certain share of wax molecules in the composite are hindered to crystallize. Furthermore, we show that the resulting material can recovery its repellent properties after surface damage.

Thickness Characterization of Steel Plate Coating Materials with Terahertz Time-Domain Reflection Spectroscopy Based on BP Neural Network.

Accurate monitoring of steel plate coating thickness is crucial in construction quality control and durability assessments. To address this challenge, this study introduces a terahertz time-domain reflection spectroscopy based on a BP neural network model to achieve a quantitative visualization characterization of coating thickness. The BP neural network eliminates the inherent dependence of terahertz reflection spectroscopy on the refractive index value in thickness calculation. This trained BP neural network model effectively establishes a functional relationship between signal feature parameters and the corresponding thickness values. Additionally, the proposed model can innovatively measure different coating materials' refractive indexes, revealing the corresponding values for the black paint, white paint, epoxy resin, and rubber as 2.212, 1.967, 1.924, and 2.185, respectively. The experimental results demonstrate the trained BP neural network model possesses remarkable accuracy in predicting coating thickness within the scanning area, achieving a precision level exceeding 96%. This method enables the visualization of coating thickness and the extraction of thickness characterization values. Furthermore, using the thickness imaging results as a reference, the method can accurately identify the thickness abnormalities across the scanning area, locating the position and size of potential defects such as internal scratches and foreign object defects. This innovative approach offers a superior means of monitoring and assessing the thickness distribution quality of the steel plate coating layer materials.

Nitrogen-rich skeleton reassembled ECOFs as energetic materials with low sensitivities and good corrosion resistance

Corrosion between energetic materials and metal containers can accelerate material aging and failure, significantly affecting the safety, reliability, and lifespan of ammunition systems. To address this challenge, we propose the construction of energetic covalent organic frameworks (ECOFs) as a promising solution. We introduce a straightforward method for synthesizing nitrogen-rich ECOFs. The synthesized ECOFs were characterized through powder X-ray diffraction (PXRD), solid-state nuclear magnetic resonance (ssNMR), and Fourier-transform infrared spectroscopy (FTIR). These frameworks exhibit remarkable thermal stability, with decomposition temperatures above 285 °C. Notably, they display low sensitivity to non-explosive stimuli, as evidenced by impact sensitivity over 60 J and friction sensitivity over 360 N. The anti-rust properties of the ECOFs were further evaluated using Tafel curve analysis, highlighting their exceptional resistance to metal corrosion. Particularly, ECOF-3, synthesized from triaminoguanidine nitrate and 5-nitro-1,3-benzenedicarboxaldehyde, stands out for its superior steel corrosion resistance. These ECOFs have potential applications as high-energy, anti-corrosion coatings materials.

Enhanced thermophysical and mechanical properties of gadolinium zirconate ceramics via non-stoichiometric design

Rare-earth zirconate ceramics are potential materials for thermal barrier coatings due to their low thermal conductivity and excellent structural stability. However, the low thermal expansion coefficient and fracture toughness limit their application and further improvements are needed. In this work, non-stoichiometric gadolinium zirconate ceramics with fluorite phase structure were successfully prepared using solid-state reaction method. HRTEM, iDPC-STEM, and in-situ XRD were employed to investigate nanostructure, lattice defects, and phase stability. The non-stoichiometric ratio introduces more defects and forms special nanostructures, enhancing the thermophysical properties of gadolinium zirconate ceramics. The non-stoichiometric gadolinium zirconate ceramics have lower phonon thermal conductivity with higher hardness and fracture toughness compared to stoichiometric ratio ceramics. In addition, the non-stoichiometric gadolinium zirconate ceramics exhibit excellent structural stability in a wide temperature range. These performances provide further applications for non-stoichiometric gadolinium zirconate ceramics as thermal barrier coatings.

Thermochemical interaction of (Yb0.7Gd0.3)4Hf3O12 ceramic with CMAS melts

The molten calcium-magnesium alumino-silicate (CMAS) deposits degradation of thermal barrier coatings (TBCs) is increasingly severe in advanced turbine engines. In this study, the thermochemical interaction of a promising TBC candidate material, (Yb0.7Gd0.3)4Hf3O12, with CMAS melts at 1300 ℃ and 1500 ℃ was systematically investigated. The apatite and reprecipitated fluorite with high melting points were crystallized rapidly when the ceramic reacted with CMAS melts, resulting in the formation of a dense crystalline layer to suppress further infiltration of CMAS melts. Moreover, as the reaction proceeded, the formation of garnet and cuspidine occurred at 1300 ℃ and 1500 ℃, respectively. The CMAS resistance of (Yb0.7Gd0.3)4Hf3O12 was significantly higher compared to that of Yb4Hf3O12, which could be attributed to the greater volume fraction of apatite and reprecipitated fluorite in the reaction products. The (Yb0.7Gd0.3)4Hf3O12 exhibited high effectiveness in mitigating CMAS infiltration, making it a potential candidate material for thermal barrier coatings.

Effects of Y doping on phase structure, mechanical properties and sintering behavior of (Yb1-xYx)2SiO5 environmental barrier coating materials

Yb2SiO5 is one of the most widely studied environmental barrier coating materials due to its excellent high-temperature phase stability and resistance to water oxygen corrosion. In this paper, a series of (Yb1-xYx)2SiO5 (x = 0, 0.1, 0.2, 0.3, 0.4) ceramics were fabricated by high-temperature solid state sintering at 1550 °C. The effects of Y doping concentration on phase composition, mechanical properties, thermal conductivity and high-temperature sintering behavior of Yb2SiO5 ceramics were investigated in detail. The results show that all the (Yb1-xYx)2SiO5 ceramic specimens are composed of single X2-Yb2SiO5 phase with relative high compactness. The introduction of Y gives rise to the reduction of the thermal conductivity of Yb2SiO5 and the value of cell parameters and volume of (Yb1-xYx)2SiO5 is proportional to the Y3+ doping concentration. Among the five (Yb1-xYx)2SiO5 ceramics, (Yb0.9Y0.1)2SiO5 possesses the lowest brittleness index and its average fracture toughness is 2.85 MPa m1/2, which is about 10 % higher than pure Yb2SiO5. In addition, (Yb0.9Y0.1)2SiO5 has good high temperature phase stability from room temperature to 1450 °C and the grain size of (Yb0.9Y0.1)2SiO5 is basically unchanged after sintering at 1400 °C for 100 h. We believe that (Yb0.9Y0.1)2SiO5 is one of the most promising candidate materials for environmental barrier coatings.

Application of Silk Fibroin Nanoparticles based Edible Coating Material for Postharvestshelf-Life Extension and Preservation of Food Products

Nanotechnology is a burgeoning discipline that adapts to fresh and improved use in food systems relative to previous technologies, despite its broad application in agriculture, biochemistry, medicine, and several industries. By implementing innovative technologies, it is possible to efficiently incorporate them into many parts of food production, development, manufacturing, packaging, storage, and distribution. Nanoparticles occupies the most fundamentally advanced technology in nano-based food science. Using a broad range of nanostructured materials and nanomethods, such as liposomes, polymeric nanoparticles, nanoencapsulation, nanotubes, nanocomposites, packaging, and nanosensors. Silk Fibroin (SF), a biomacromolecule based on proteins, is very biocompatible, biodegradable, and has a low immunogenicity. Due to these characteristics, silk fibroin nanoparticles, or SFNPs, are beneficial across several sectors, including medical and food. The creation of SF-based nanoparticles as edible coating materials extends food shelf life and protects food components while also fortifying and supplementing nutrients. The phytochemical activities of SFNPs, including their antibacterial and antioxidant properties, are summarized in this review. The possible uses of silk fibroin nanoparticles in food, such as food additives and food packaging, which may be able to meet customers increasing demands about the food’s safety and nutritional value. The techniques of food preservation used to preserve or safeguard food quality are the major topic of this review article. Natural food preservatives are also discussed as a safer alternative to chemical preservatives for human consumption.

The Use of Polyurethane Composites with Sensing Polymers as New Coating Materials for Surface Acoustic Wave-Based Chemical Sensors—Part III: Ultrasonic Analyses and Optical Microscopy Characterization of the Coating Results

The chemical sensitization of surface acoustic wave (SAW) sensors plays a key role for this technology. The analysis of the resulting nanometric sensing layer is crucial for the development of new sensing materials as well as for the quality control of SAW sensors systems for commercial applications. In the previous works, the resulting coating layers using new coating materials based on polyurethane-polymer composites were evaluated considering the ultrasonic analysis, the adhesion, and the sensor responses. In this work, the characterization of the coating process, Bright Field Microscopy (BFM) and Dark Field Microscopy (DFM) were used to evaluate the quality of the material distribution and homogeneity of the obtained sensing layers. The sensing materials analyzed were the four polymers used in the previous works and their respective new composites with polyurethane (PU). The combination of BFM and DFM allows the characterization of the resulting material distribution obtained by the coating process, providing inferences about the interaction of each coating material with the surface of the SAW sensor element as well as about the correlation between the results of the ultrasonic parameters, the real material distribution and the homogeneity of the obtained coating layer of each coating material.

Synthesis and characterization of sustainable polyurethane-amide (PUA)-organoclay bio-nanocomposites for enhanced protective coatings

An effort has been made to synthesize sustainable polyurethane-amide (PUA) organoclay by incorporating natural materials. Polyol derived from castor oil, toluene diisocyanate (TDI), and cetyl pyridinium chloride (CPC) modified Montmorillonite (Mt) clay have been used in this purpose. The modification of Mt clay with CPC serves a dual purpose by increasing the D-spacing between clay layers and enhancing the compatibility of clay with organic polymers. The investigations included varying the percentage of TDI at three different levels to assess its impact on the physical, mechanical and corrosion resistance characteristics of bio-nanocomposite. The presence of characteristics CH bonds at 2854 cm−1 (sym. −CH2) and 2928 cm−1 (asym. −CH2–) in CMC are absent in Mt, confirming formation of CPC modified Mt clay (CMC). Structural investigations of nanobiocomposites were done by Scanning electron microscopy and X-ray diffraction studies and TGA analysis. The findings suggest that the synthesized bio-nanocomposites could serve as a novel and environmentally friendly material for protective coatings.

Application of Waterborne Epoxy Resin Modified Bitumen Emulsion as a Tack Coat Material

Application of Waterborne Epoxy Resin Modified Bitumen Emulsion as a Tack Coat Material

Analysis the Effect of Different Surface Preparation Methods on Corrosion Resistance and Adhesion Strength of ASTM A36 Steel Substrate with Surface Tolerant Epoxy Paint as Coating Material

In the industrial world, to extend the service life of materials, protection methods are carried out to slow down the material's corrosion rate. The protection method that is often used is the coating method. The coating method is a protection method by coating the substrate material using a coating material to prevent contact between the substrate material and the environment. In this research, the substrate material used is ASTM A36 steel and the coating material used is Surface Tolerant Epoxy paint. The independent variable used in this study lies in the surface preparation method which consists of: solvent cleaning, hand tool cleaning, power tool cleaning, power tool to bare metal cleaning, and abrasive blast cleaning. Different preparation methods result in different roughness and cleanliness of the surface. This can affect changes in the mechanical properties of the coating material, such as corrosion resistance and adhesion strength. Based on the corrosion resistance test, it is found that the abrasive blast cleaning and power tool to bare metal cleaning methods produce the highest corrosion resistance properties because both have a rating number of 8 in the salt spray test results. Based on the adhesion strength test, it is found that the abrasive blast cleaning method also produces the highest adhesion strength. This conclusion refers to the results of the tape x-cut test where the sample produces a rating number 5A where the sample does not experience peeling after testing. In addition, the abrasive blast cleaning method produced the highest adhesion strength in the pull-off test, which was 7.16 Mpa. Thus, the abrasive blast cleaning method is the most effective surface preparation method for ASTM A36 steel before being coated with the coating material. In addition, it can also be concluded that the higher the surface roughness of the sample, the better the corrosion resistance and adhesion strength.

Elucidating the Influence of Coating Materials in the Microencapsulation Process of Hempseed Oil Via Spray Drying: A Comprehensive Analysis of Physicochemical Attributes, Oxidation Stability, and Thermal Properties

In this study, it was aimed to investigate the effect of different coating materials on the microencapsulation of hempseed oil by spray drying. For this purpose, hempseed oil emulsions were prepared with skimmed milk powder (SMP), maltodextrin (MD), and whey protein concentrate (WPC). The properties of these emulsions including rheological, zeta potential, and physicochemical properties were analyzed. Then, hempseed oil microcapsules were produced using spray drying. The effect of the different coating materials on spray-dried hempseed oil capsules was evaluated in terms of microencapsulation yield, surface oil, microencapsulation efficiency, oxidation stability, and physicochemical properties. The combinations of SMP (50.58%) or WPC (56.21%) with MD significantly enhanced the microencapsulation yield. The highest microencapsulation efficiency (92.16%) was obtained in the microcapsule with SMP: MD. This microcapsule with SMP: MD also showed higher oxidative stability compared to other microcapsules. Besides, this combination (SMP: MD) effectively protected the hempseed oil against oxidation during the Schaal oven test. Additionally, spray-dried hempseed oil microcapsules were characterized using FT-IR, TGA, and SEM. It was determined that using MD as a coating material improved the thermal stability of the microcapsules. As a result, it was concluded that the SMP: MD as a coating material was suitable for the microencapsulation of hempseed oil.

Development of an epoxy resin-based anticorrosive coating enhanced by monolayer amino-modified graphene oxide

Epoxy resin (EP) serves as a prevalent material for anti-corrosion coatings, yet its corrosion resistance demands further refinement. In this work, monolayer amino-modified graphene oxide with an average height of 0.930 nm and 1.023 nm was synthesized using urea and melamine, named NGO and MGO, respectively. When incorporated into EP coatings, the NGO and MGO exhibit outstanding protective properties. The impact of different concentrations of NGO and MGO on the corrosion resistance of EP coated Q235 samples were meticulously examined. Through electrochemical measurements and salt spray tests, it was determined that the coatings containing 0.1 wt% NGO or 0.3 wt% MGO exhibited remarkable corrosion resistance. Furthermore, we conducted a comparative analysis of the corrosion resistance between the NGO and MGO composite EP coatings. Following immersion in a 3.5 wt% NaCl solution for 240 h, the impedance modulus at low frequencies (|Z|0.01 Hz) of the MGO composite coating was approximately two orders of magnitude greater than that of the NGO composite coating. Even following an extended immersion period of 480 h, the |Z|0.01 Hz for MGO-EP continued to maintain an advantage of one order of magnitude.

The Use of Polyurethane Composites with Sensing Polymers as New Coating Materials for Surface Acoustic Wave-Based Chemical Sensors—Part II: Polyurethane Composites with Polylaurylmetacrylate, Polyisobutene, and Poly(chlorotrifluoroethylene-co-vinylidene Fluoride): Coating Results, Relative Sensor Responses and Adhesion Analysis

This work presents the application of the methodology for the sensitization of surface acoustic wave-based sensors (SAW), developed in the first part of this work. The strategy of the method is the obtention of sensing layers with tailored chemical environments by taking advantage of the wide variety of chemical composition of the organic polymers, which have been used as sensing polymers, and combining them with polyurethane (PU) to form polymeric composites that show enhanced properties as sensing materials for the SAW sensor technology. In the first part of this work, the ultrasonic and adhesion characterization was correlated to the sensor responses of PU-polybutylmethacrylate (PBMA) composites of different relative concentrations of the sensing polymer (PBMA) and PU. The resulting coating layers obtained with the PU polymer composites improved the chemical and mechanical properties of the sensing layer without interfering with the quality of their sensor responses in comparison to those with the pristine polymer as the sensing material. In this second part of this work, three new polyurethane polymeric composites were analyzed. The new sensing materials were produced using polylaurylmetacrylate (PLMA), polyisobutene (PIB), and poly(chlorotrifluoroethylene-co-vinylidene fluoride) (PCTFE) as the sensing polymers combined with PU. The results of the new PU polymer composites showed consequently different properties depending on the type of sensing polymer used, reproducing, however, the previous features achieved with PU and polybutylmetacrylate (PBMA) composites, like the improvements in the adhesion and the resistance against an organic solvent and preserving, in each case, the sensor response characteristic of each sensing polymer used, as was also observed for the PU-PBMA polymeric composites. The results obtained with the new sensing materials validated the strategy and confirmed its generalization as a very suitable methodology for the sensitization of SAW sensors, strongly indicating the applicability and reliability of the method, which makes possible the choice of virtually any chemical environments for the sensitization of SAW sensor systems.

Novel Resin-Based Antibacterial Root Surface Coating Material to Combat Dental Caries.

Root caries caused by cariogenic bacteria are a burden on a large number of individuals worldwide, especially the elderly. Applying a protective coating to exposed root surfaces has the potential to inhibit the development of caries, thus preserving natural teeth. This study aimed to develop a novel antibacterial coating to combat root caries and evaluate its effectiveness using the antibacterial monomer dimethylaminohexadecyl methacrylate (DMAHDM). DMAHDM was synthesized and incorporated into a resin consisting of 55.8% urethane dimethacrylate (UDMA) and 44.2% TEG-DVBE (UV) at a 10% mass fraction of glass filler. Multiple concentrations of DMAHDM were tested for their impact on the resin's mechanical and physical properties. S. mutans biofilms grown on resin disks were analyzed for antibacterial efficacy. Cytotoxicity was assessed against human gingival fibroblasts (HGFs). The results showed an 8-log reduction in colony-forming units (CFUs) against S. mutans biofilm (mean ± sd; n = 6) (p < 0.05) when 5% DMAHDM was incorporated into the UV resin. There was a 90% reduction in metabolic activity and lactic acid production. A low level of cytotoxicity against HGF was observed without compromising the physical and mechanical properties of the resin. This coating material demonstrated promising physical properties, potent antibacterial effects, and low toxicity, suggesting its potential to protect exposed roots from caries in various dental procedures and among elderly individuals with gingival recession.

Development of Biocomposite Food Packaging Coating Material with Silane-treated Nanosilica and Grape Seed Oil Blended Vinyl Ester

Development of Biocomposite Food Packaging Coating Material with Silane-treated Nanosilica and Grape Seed Oil Blended Vinyl Ester

Advanced rare earth tantalate RETaO4 (RE=Dy, Gd and Sm) with excellent oxygen/thermal barrier performance

Thermal barrier coatings (TBCs) materials with lowered thermal and oxygen ion conductivity can provide thermal and oxidative protection for high temperature hot-end components in aeronautical engines and gas turbines. The rare-earth tantalate RETaO4 (RE = Dy, Gd and Sm) ceramics with monoclinic (m) phase were successfully synthesized via spark plasma sintering. Oxygen vacancies responsible for the thermal and oxygen ion conductivities of RETaO4 were demonstrated by atomic-resolution energy dispersive X-ray and X-ray photoelectron spectroscopy. Among the three samples, DyTaO4 has excellent oxygen/thermal barrier performance. Compared to the current service thermal barrier coating material ZrO2-8 wt% Y2O3 (8 YSZ), DyTaO4 has an ultra-low oxygen ion conductivity benefiting from low oxygen vacancy concentration and strong stretching force constants. The intrinsic thermal conductivity of DyTaO4 is 68.2% less than that of 8 YSZ. Additionally, the thermal expansion rate curves indicate that the phase transformation does not happen from room temperature to 1200 °C. The above results demonstrate that high-growth rate thermally grown oxide can be retarded by creating dense DyTaO4 coating with lowered thermal and oxygen ion conductivity.

The enhanced mechanical properties for Hf6Ta2O17 thin film through component segregation

With outstanding thermal and mechanical properties, Hf6Ta2O17 emerges as an ideal candidate for next-generation thermal barrier coatings (TBC) material. However, high-temperature process during TBC fabrication will inevitably lead to Ta2O5/HfO2 component segregation because large differences in vapor pressure. In this paper, Hf6Ta2O17 polycrystalline film with different Ta2O5/HfO2 component was prepared on sapphire substrate by sol-gel method through spin coating. Morphological analysis indicates the excessive Ta2O5 can reduce the porosity in Hf6Ta2O17 thin film through eutectic process, while excessive HfO2 will lead to a worse morphology and smaller average grain size. Nanoindentation reveals that component segregation of excessive Ta2O5/HfO2 could both be used to strengthen of Hf6Ta2O17 through different mechanisms. In addition, a higher elastic recovery rate in excessive Ta2O5 system indicates Ta2O5Hf6Ta2O17 eutectic system could accelerate energy dissipation and further enhance the toughness for Hf6Ta2O17. This work provides a deep insight into the strengthening mechanism of ceramics Hf6Ta2O17 with component segregation and paves the way to design of next-generation TBCs.