Coat Components Research Articles

Теоретичне обґрунтування експлуатаційних властивостей деталей автомобілів, зміцнених композиційними покриттями, методом кластерних компонентів

A number of parts of car systems and units in the process of operation are subject to intensive wear and fatigue processes, and therefore do not withstand the planned service life. An important reserve for increasing the reliability and efficiency of such equipment is the strengthening of the working surfaces of its parts with composite materials and coatings. This method of strengthening makes it possible, controlling the structure of composite materials and coatings, to form the necessary set of performance properties of parts to ensure the appropriate level of reliability and increase durability. However, this requires theoretical justification to establish a correspondence between the structure, composition, distribution of chemical elements applied to the parts of the composite coating and their performance properties, such as wear resistance, fatigue strength, etc. The purpose of this work is a theoretical justification for the use of the method of cluster components to determine and form a set of necessary performance properties that ensure reliable and efficient operation of parts of systems and units of cars. The article theoretically substantiates the operational properties of automobile parts hardened with composite coatings using the method of cluster components. By choosing certain sets of parameters, as well as varying the system of restrictions on them, it is possible to form a complex of operational properties of parts. To simplify the packing model for composite materials and coatings, it is assumed that fillers of different compositions have an isometric shape and the same size. A regular structure is proposed, corresponding to the packing of spheres of the same size. It is shown that such packings form lattices similar to atomic crystal structures. The dependences of the function of the properties of composite coatings on the content of each of the types of cluster components are revealed. The method of cluster components, describing changes in the properties of composite coatings from the ratio of components, makes it possible to control a set of operational properties and obtain high-quality coatings to increase the durability of parts of systems and vehicle units. As a result of the conducted researches it is offered to consider composite coverings and composite materials as the systems characterized by a certain complex of operational properties depending on filler content and regularity of structure. According to the theory of cluster components, the content of the component determines the parameters and properties of composite coatings and materials. The method of cluster components makes it possible to present a set of operational properties as an additive model of its components. The packaging of components in composite coatings and materials is represented by atomic crystal structures: simple cubic, volume-centered cubic, face-centered cubic and hexagonal densely packed. The implementation of the method of cluster components on the example of a binary system of components A and B is considered. The basic configuration in accordance with the approximations of the statistical ordering theory is chosen. The visual interpretation and physical content of a mixture of powders, components of composite coatings and materials, particles A and B are given. The configurational entropy and formation of cluster components of the intermediate composition AB along with the basic AA and BB are considered. Based on the π-theorem, a complete set of quasi-chemical reactions is outlined. For binary composite coatings and materials АСВ1-С the matrices of size and relative content of components are constructed, the quasi-chemical formalism of the method of cluster components and the law of active masses for volume-centered cubic lattice are used. This is taken into account when building functional models of operational properties. Their specification on the criterion of correctness is carried out.

The influence of ceramic additives on intumescence and thermal activity of epoxy coatings for steel

AbstractThe article presents results of the research on the influence of graphite/kaolin and graphite/titanium oxide systems on thermal properties, intumescence degree and the integrity of the structure of intumescent protective films based on epoxy resins for steel. The TG/DTG/DSC analysis showed that graphite/kaolin system shifted the decomposition reaction of epoxy resin towards higher temperatures, even by about 30°C. Fire endurance tests and the SEM analysis confirmed these results because more thermally resistant (T500°C reached after 37.5 min for 1.1 coating thickness), swollen (about 20 times) and homogeneous coatings were obtained. The presented results suggest that ceramic fire retardants can successfully cooperate with organic components in intumescent protective coatings for steel elements.

Protective Properties of Alkyd Coatings Inhibited by Complex Zeolite-Phosphate Pigment

We study a complex anticorrosion pigment based on calcium-containing zeolite with zinc phosphate precipitated on its nanoporous surface. It is discovered that this pigment efficiently retards corrosion in an aluminum alloy placed in a synthetic acid medium and inhibits the subfilm corrosion of the metal near defects of the alkyd paint coating. The proposed pigment may serve as a promising inhibiting component of paint coatings aimed at the protection of structures made of aluminum alloy in the industrial atmosphere.

Hardness, microstructure and texture of friction surfaced 17-4PH precipitation hardening stainless steel coatings with and without subsequent aging

Precipitation hardening stainless steel 17-4PH coatings were successfully deposited on the AISI 304 substrate via friction surfacing (FS) for enhancing the surface hardness. Through FS, the incoherent precipitates (Cu and CrN, 25–50 nm) originally existed in the as-received (AR) 17-4PH consumable rod (345 HV1) were re-dissolved into the martensitic matrix of the FSed 17-4PH coatings (400 HV1). The strain incompatibility caused by severe plastic deformation (SPD) in FS induced the formation of Cr-rich (Ni and Cu-depleted) δ-ferrite (1.8–2.7%) along the plastic flow direction with stress concentration. The shear deformation and dynamic recrystallization (DRX), as evidenced by the−J shearing and RTc’ recrystallization components in the FSed coatings, refined the grain size of the prior austenite. Increase in hardness of the FSed coatings was mainly attributed to the high dislocation density introduced by SPD. There was 4.8% acicular reversed austenite formed displacively, which possessed Kurdjumov-Sachs (K-S) relationship with surrounding martensite in the AR 17-4PH rod after solutionized treatment (ST) and aging (H900). The hardness of the AR 17-4PH after H900 was increased (439 HV1) because of the increment of dislocation density and micro-strain in the martensitic matrix introduced by the early-stage precipitation of coherent Cu. Owing to existence of δ-ferrite in the FSed coatings, some globular reversed austenite formed diffusively besides acicular ones after H900. There was more austenite (9.2%) in the FSed coating after H900 (456 HV1). The globular reversed austenite, which nucleated on the shear deformed martensitic grains in the FSed coatings, possessed {110}fcc//{120}bcc with adjacent δ-ferrite. SPD-induced dislocations in the FSed coating were annihilated during H900 leading to decrease in hardness but compensated by the precipitation hardening of coherent Cu. After FS, the micro-scale MnS and NbP2S8 inclusions in the AR 17-4PH were broken into nano-sized fragments which were dissolved into martensitic matrix during H900.

Optical properties of sol-gel coatings containing silver nanoparticles

The technology of receiving the antireflective coating increasing efficiency of use of sunlight in various service conditions is described. Suspensions of nanodimensional silicon dioxide with tetraethoxysilane as a precursor were synthesized to solve the assigned task. The received suspensions were applied by a dipping method on glass samples followed by the coating formation on a surface of the substrates at various temperatures. As a result of a cure of the received samples under natural conditions transparent film of about 500 nanometers thick having very low strength properties on the surface of glass were formed. Heat treatment led to the improvement of strength of coatings in process with increase of temperature up to 600 °C. Exceeding of this temperature resulted in cracking of coatings. In the course of heat treatment higher than 300 °C formation of a coating was accompanied by the thermolysis of silver nitrate that was introduced into silicon dioxide suspension with a formation of silver particles which size was in the nanoscale distance limits according to the results of Auger electron spectroscopy. Presence of evenly distributed silver nanoparticles provided an antireflective effect to coatings which at visual observation found expression in the form of the interference phenomenon. The obtained data confirmed prospects of use of nanosilver as a component of coatings on the basis of silicon dioxide in order to confer the antireflective properties.

The Micro-Scaled Characterization of Natural Terrestrial Ferromanganese Coatings and Their Semiconducting Properties

Different types of ferromanganese coatings were collected from the Chinese mainland to study their mineralogical characteristics and semiconducting properties. Measurements, including by optical microscope, scanning electron microscope, energy dispersive X-ray spectroscopy, micro-Raman spectrometer and transmission electron microscope, were employed to study their morphology, mineral assemblage, element abundance and distribution patterns. Soil Fe coatings are mainly composed of Al-rich hematite and clays. Soil Fe/Mn coatings can be divided into an outer belt rich in birnessite and an inner belt rich in hematite, goethite, ilmenite and magnetite. Goethite is the only component of rock Fe coatings. Rock Fe/Mn coatings mainly consist of birnessite and hematite, and alternating Fe/Mn-rich layers and Fe/Mn-poor layers can be observed. Powders were scraped off from the topmost part of ferromanganese coatings to conduct laboratory photochemical experiments. The photocurrent–time behavior indicates that natural coating electrodes exhibit an immediate increase in photocurrent intensity when exposed to light irradiation. Natural coatings can photo-catalytically degrade 14.3%–58.4% of methyl orange in 10 h. Under light irradiation, the photocurrent enhancement and organic degradation efficiency of the rock Fe/Mn coating, which has a close intergrowth structure of Fe and Mn components, is most significant. This phenomenon is attributed to the formation of semiconductor heterojunctions, which can promote the separation of electrons and holes. Terrestrial ferromanganese coatings are common in natural settings and rich in semiconducting Fe/Mn oxide minerals. Under solar light irradiation, these coatings can catalyze important photochemical processes and will thus have an impact on the surrounding environment.

Basic principles of replication and immunology of SARS-CoV-2

Coronaviren sind eine in Wirbeltieren beheimatete, genetisch hochvariable Virusfamilie, der es mehrfach gelungen ist, durch Überwindung der Artenbarriere den Menschen zu infizieren. Das Ende 2019 zuerst in China aufgetretene „Severe Acute Respiratory Syndrome-Coronavirus-2“ (SARS-CoV-2) zeichnet sich durch hohe Infektiosität und Pathogenität gegenüber verwandten Vorläufern aus. Da die Virushülle und andere Virusbestandteile vom Immunsystem als fremd erkannt werden, kann dies zu einer ersten Symptomatik führen, die über die im respiratorischen Epithel sehr effizient arbeitende Immunabwehr induziert wird. Im Rahmen schwerer Verläufe kann es zu einem systemisch ausgeprägten proinflammatorischen Zytokinsturm und nachfolgenden Veränderungen des Gerinnungs- und Komplementsystems kommen. Virusspezifische Antikörper, deren langfristige Expression über die Ausbildung von B‑Memory-Zellklonen gesichert wird, generieren eine spezifische Immunantwort, die auch im Blut nachweisbar ist (Serokonversion). Ebenso bilden sich spezifisch wirksame zytotoxische CD8+-T-Zell-Populationen aus, die Viruspeptide als pathogenspezifische Muster in Verbindung mit MHC-Präsentation auf der Zelloberfläche virusbefallener Zellen erkennen und diese Zellen abtöten. Unklar ist zum jetzigen Zeitpunkt noch, wie regelhaft, robust und dauerhaft dieser Immunstatus aufgebaut wird. Die Erfahrungen mit anderen Coronavirus-Infektionen (SARS und MERS) deuten darauf hin, dass die Immunität mehrere Jahre anhalten könnte. Aufgrund von Tierversuchen, bereits erhobenen Daten zu anderen Coronavirustypen sowie Plausibilitätsannahmen kann davon ausgegangen werden, dass serokonvertierte Patienten eine zeitlich begrenzte Immunität und ein nur sehr geringes Reinfektionsrisiko haben. Das Wissen um die molekularen Mechanismen von Viruszyklus und Immunität stellt eine wichtige Voraussetzung bei der Entwicklung von Impfstrategien und der Wirkstoffentwicklung dar.

Cultural heritage protection via hybrid nanocomposite coating

ABSTRACT Historical constructions are exposed to weathering conditions and atmospheric pollution for many years which demolish the historical material as well as dramatically influence their visual aspects. Nowadays, the development of conservative coatings with weather-resistant, self-cleaning, and hydrophobic properties is a promising challenge for carbonate stones. In this study, a simple synthesis route is developed to obtain organic–inorganic hybrid nanocomposites. The main components of the acrylate coatings are methyl methacrylate, 3-(trimethoxysilyl)propyl methacrylate (TMSM). Tetraethyl orthosilicate (TEOS) is added to the coating to improve the thermal resistance of the coating. Perfluorooctyl-trichlorosilane (FOTCS) is added to the coating to improve the weathering resistance and hydrophobic behaviour of the coating. Also, titanium dioxide (TiO2) is added to improve the thermal resistance and photocatalytic feature of the coating. The results confirmed significant enhancement in contact angle and weathering resistance that originates from adding an organofluorine component in the structure of the coating. A hybrid coating includes acrylate monomers as the binder and chemical substances include an organosilane (TEOS), fluorinated silane (FOTCS) and titania nanoparticles (TiO2) has appropriate properties like thermal resistance, mechanical resistance, weathering resistance, hydrophobicity, and self-cleaning that can be used as a protective coating for the precious stone-made cultural heritages.

Development of sustainable polyols with high bio-renewable content and their applications in thermoset coatings

In recent years, bio-renewable based materials have been increasingly explored as a promising replacement for petroleum-based ones used as building blocks for polymers. This trend is mainly driven by the increasing awareness and directives for the sustainable development of polymeric materials, including coatings. The lower carbon footprint compared to their petroleum counterparts and depleting known resources of petroleum makes bio-renewable materials very important for future development. However, it is very important to meticulously design polymers based on bio-renewable building blocks by leveraging their unique chemistry and functionality, to meet the demanding requirements of the final products at acceptable costs.In the present work, by combining unique features and functionalities of two low-cost commercial commodity bio-renewable based materials - Epoxidized soybean oil (ESO) and rosin – polymeric polyols with bio-renewable content > 78 % by weight have been successfully developed. A series of single-component melamine-formaldehyde (MF) cured thermoset coatings have been then formulated and evaluated. Some of the prepared coatings demonstrated excellent adhesion (5B), high MEK-Double-Rubs (100–200), high gloss @ 60° (>80), and promising flexibility and impact resistance properties (140−160 lb.in). The outcome of this study clearly demonstrates the suitability of these polyols as primary components of sustainable industrial coatings.

Microstructure and morphology evolution of high-Z/low-Z gradient coatings on PAMS microspheres

Gradient coatings exhibit excellent implosion performance in double-shell targets for Inertial Confinement Fusion (ICF). Here, we present the controllable preparation of high-Z/low-Z (Z is the atomic number) gradient alloy coatings which can be used for ICF double-shell targets. Tungsten/carbon (W/C), tungsten/silicon (W/Si) and tungsten/aluminum (W/Al) gradient coatings were successfully deposited on silicon substrates and poly-alpha-methyl-styrene (PAMS) spheres by direct-current magnetron sputtering. The morphology, component and surface roughness of gradient coatings were characterized. Although there are significant differences in morphology and surface roughness compared with planar gradient coatings, the spherical gradient coatings still have a dense microstructure and smooth surface. The root-mean-square (RMS) roughness of our gradient coatings experience an improvement compared with the previous films which used in ICF experiments. The gradient coatings deposited by co-sputtering of high-Z and low-Z elements in this work provide competitive candidate materials for ICF double-shell targetsee.

Liposome Binding Assay to Characterize the Structure and Function of Cavin Proteins.

Protein-protein and protein-lipid interactions play important roles in the assembly of protein coats that regulate membrane organization, signaling, and trafficking in eukaryotic cells. Caveolae are plasma membrane invaginations that are formed by a protein coat consisting of caveolin and cavin protein complexes. The biochemical and structural principles of membrane binding by coat components can be studied through in vitro reconstitution of purified proteins and lipid vesicles. In this chapter, we describe a method to isolate peripheral cavin coat complexes and to subsequently bind purified cavin to chemically defined liposomes. The cavin proteoliposomes can be further analyzed to gain insights into lipid binding specificity, membrane-remodeling properties, and structural characteristics of the cavin family members.

Modified phenolic resins and their compatibility with the components of epoxy-phenolic protective coatings

Modified phenolic resins and their compatibility with the components of epoxy-phenolic protective coatings

Vesicular and uncoated Rab1-dependent cargo carriers facilitate ER to Golgi transport.

ABSTRACTSecretory cargo is recognized, concentrated and trafficked from endoplasmic reticulum (ER) exit sites (ERES) to the Golgi. Cargo export from the ER begins when a series of highly conserved COPII coat proteins accumulate at the ER and regulate the formation of cargo-loaded COPII vesicles. In animal cells, capturing live de novo cargo trafficking past this point is challenging; it has been difficult to discriminate whether cargo is trafficked to the Golgi in a COPII-coated vesicle. Here, we describe a recently developed live-cell cargo export system that can be synchronously released from ERES to illustrate de novo trafficking in animal cells. We found that components of the COPII coat remain associated with the ERES while cargo is extruded into COPII-uncoated, non-ER associated, Rab1 (herein referring to Rab1a or Rab1b)-dependent carriers. Our data suggest that, in animal cells, COPII coat components remain stably associated with the ER at exit sites to generate a specialized compartment, but once cargo is sorted and organized, Rab1 labels these export carriers and facilitates efficient forward trafficking.This article has an associated First Person interview with the first author of the paper.

Modified phenolic resins and their compatibility with the components of epoxy-phenolic protective coatings

Modified phenolic resins and their compatibility with the components of epoxy-phenolic protective coatings

A review of cellulose nanomaterials incorporated fruit coatings with improved barrier property and stability: Principles and applications

AbstractFresh fruit are rich in vitamins, minerals, and phytochemicals, but are highly perishable. Due to the great need for improving storability of fresh fruit, it is necessary to develop cost effective coating technology with targeted moisture and gas barrier, mechanical and other desirable properties to satisfy specific postharvest physiological need and storage conditions of a given fruit. Cellulose nanomaterials (CNs) present distinguished intrinsic properties, including low density, high aspect ratio, high mechanical property, superior gas and moisture barrier, and good thermal stability. For these reasons, applications of CNs in fruit coatings show great promises for improving quality and storability of postharvest fresh fruit under various storage conditions. This review discussed the principles and mechanisms of CNs role in food packaging films and coatings, applications of CNs‐incorporated coatings in a wide range of fruit, and the safety, regulations, and future perspectives of CNs‐incorporated fruit coating technologies.Practical ApplicationCellulose nanomaterials (CNs), including cellulose nanofibers (CNF) and cellulose nanocrystals (CNC), have great potential as components in fruit coatings for improving barrier, stability, and other functional properties. This review introduced the potential roles of CNs in fruit coating technology as coating matrix, filler for other biopolymers, Pickering emulsion agent, and/or crosslinking agent, thus the principles and mechanisms of using CNs in fruit coatings. This review also reported the recent research and development in CNs‐incorporated fruit coatings, and discussed the hurdles and future perspectives of using CNs in fruit coatings. This review provided most updated information and important insights of CNs‐incorporated coatings, which is critical for developing effective coating technologies for ensuring quality and improving storability of fresh fruit.

Effect of pack cementation temperatures on component, microstructure and anti-oxidation performance of Al-modified SiC coatings on C/C composites

SiC coatings doped with Al were synthesized on the C/C composites using the pack cementation technique. We explored the microstructure, composition, as well as anti-oxidation performance of Al-doped SiC coatings with different preparation temperatures (1500–2100 °C). The results prove that the coatings prepared at 1500–1900 °C are discontinuous 3C–SiC/2H–SiC/C/Si/Al2O3 coatings with some holes and micro-cracks, while the coating prepared at 2100 °C is Al atoms dissolved 4H–SiC coating with inconspicuous cracks and a loose and porous surface structure. And the coating thickness and oxidation resistances are enhanced with increasing the pack cementation temperatures. Besides, the oxygen diffusion via the coating's invisible microdefects is the leading cause of the coating's oxidation produced at 2100 °C. The coating gained at 2100 °C shows the best anti-oxidation properties owing to the in situ formed Al2O3 as well as SiO2 oxide layer on their surface.

An experimental study of the effects of topcoat on aging and fire protection properties of intumescent coatings for steel elements

This paper presents the results of an experimental study to investigate the effects of topcoat on anti-aging and fire protection properties of intumescent coatings for steel elements. Intumescent coatings with different layers of two types of topcoat were applied to steel plates. They were exposed to different cycles of hydrothermal aging before being tested in fire. The fire protection property of intumescent coatings was characterized quantitatively by effective constant thermal conductivity. A series of chemical analysis tests (DSC, FTIR and XPS) were also conducted to help understand the effects of topcoat on the degradation mechanisms of intumescent coatings. The chemical analysis test results reveal that topcoat can limit migration of hydrophilic components of intumescent coatings and therefore improve anti-aging properties of the coatings. Based on analysis of effective constant thermal conductivity, it was found that the fire protection performance of fresh intumescent coatings with 3 or 4 layers of type P (thermoplastic) topcoat was maintained throughout different cycles of aging. For type S topcoat, applying 2 layers of topcoat could almost ensure that there would be no increase in fire risk to structural safety due to aging of intumescent coatings.

Corrosive and tribocorrosive behavior of plasma powder coatings

Purpose. To investigate corrosion and tribocorrosion characteristics of plasma-powder coatings on the basis of iron, nickel and Fe-Ni system in the envyronments containing chlorides, hydrogen sulfide and ammonia. Metodology: corrosive-electrochemical, tribological, metallographic methods have been used.Results It was established that as the pH of the solution increases, the corrosion resistance of the coatings increases. The highest corrosion resistance has a surfaced layer based on nickel 06Х17Н80С3Р3, however, under tribocorrosion conditions, fragile component of coatings form an abrasive in the friction zone that intensifies the destruction. Compared to others, the coating 06Х17Н80С3Р3 has the lowest resistance to corrosion-mechanical destruction.The fragile component is absent in layers, deposited from powders 01H17N8S6G and 08Х17Н35С3Р. The solid phases are uniformly distributed in a plastic matrix corresponding to the Sharpi-Bochvar rule. In this coatings, the contact interaction occurs in the absence of abrasive wear, which explains the high resistance to tribocorrosion.It is possible to qualitatively evaluate the processes of formation and destruction of secondary structures in the friction zone of tribocorrosion by comparing of the corrosion potentials, tribocorrosion potentials and passivation potentials. Additional information may be provided by the level of local oscillations of the tribopotential, which characterizes the repassivation rate.Practical result. A new composition 08Х17Н35С3Р3 for plasma-powder coatings has been proposed to increase the wear and corrosion resistance of steel surface.

Integrating nanodiamonds to improve anticorrosion property and conductivity simultaneously of Ag composite films via layer by layer spin-spray deposition

In this paper, layer by layer spin-spray (LbLSS) deposition is developed to fabricate Ag/NDs composite films on polyethylene terephthalate (PET) surfaces. Component, morphology, thickness and adhesion of the composite coatings were investigated by X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscope, atomic force microscope and cross-cut test, respectively. The adhesion strength between composite films and substrates increased dramatically with the effects of molecular grafting and chemical etching treatment. Thickness of the Ag/NDs composite films made by 200 passes spray could be adjusted as 350 nm. The conductivity was improved by 27.7% compared to pristine Ag films. According to potentiodynamic polarization curves and electrochemical impedance spectroscopy, anticorrosion property of Ag/NDs composite films was enhanced significantly due to the introduction of NDs, especially for the polarization resistance, which was 2.213 × 106 Ω·cm2 for Ag/NDs-5 composite films and about 20 times higher than that of pristine Ag films. On basis of these promising results, the introduction of NDs improved both conductivity and anticorrosion property of silver-based films. Therefore, Ag/NDs composite films pave the way for the development of flexible electronics with excellent conductivity and anticorrosion property.

Thermogravimetry and Mass Spectrometry of Extractable Organics from Manufactured Nanomaterials for Identification of Potential Coating Components.

Manufactured nanomaterials (MNMs) often have a surface-chemical modification in order to tailor their physicochemical properties, including also powder properties and miscibility. Surface-chemical modifications may influence the toxicological properties of the MNM, but the specific chemistry and extent are rarely described in detail in suppliers’ technical data sheets. Chemical and quantitative information on any surface-chemical treatment, coating and functionalization are required for chemicals registration in Europe. Currently there is no globally accepted and documented approach to generate such data. Consequently, there is a continued research need to establish a structured approach to identify and quantify surface-chemical modifications. Here we present a tiered approach starting with screening for mass-loss during heating in a furnace or thermogravimetric analysis (TGA) followed by solvent extraction, and analysis by several mass spectrometry (MS) techniques depending on the target analytes. Thermal treatment was assumed to be able to quantify the amount of organic coating and MS was used to identify the extractable organic coatings after pressurized liquid extraction (PLE) using methanol at 200 °C. Volatile organic compounds in extracts were identified with gas chromatography and MS (GC-MS), non-volatile organic compounds with liquid chromatography MS (LC-MS), and polymeric compounds with matrix-assisted laser desorption ionization time-of-flight MS (MALDI-TOF-MS). The approach was demonstrated by analysis of 24 MNM, comprising titanium dioxide, synthetic amorphous silica, graphite, zinc oxide, silver, calcium carbonate, iron oxide, nickel-zinc-iron oxide, and organoclay. In extracts of 14 MNMs a range of organic compounds were identified and the main groups were silanes/siloxanes, fatty acids, fatty acid esters, quaternary ammonium compounds and polymeric compounds. In the remaining 10 MNMs no organic compounds were detected by MS, despite the fact an organic coating was indicated by TGA.