Advances in nano thermal analysis of coatings

This article discusses AFM-based localized thermal analysis of crosslinked polymer coatings based on a recent breakthrough in nanoscale thermal probe technology. The addition of a thermal tip to a conventional AFM adds a new and valuable capability of spatially resolved thermal analysis to the AFM. It is particularly useful for thin films since it enables the measurement of transition temperatures (melting (T _m) or glass (T _g)) on selected regions of the sample aiding in the identification and characterization of phases on the length scales approaching macromolecular dimensions. Examples include the monitoring of the softening point of automotive clearcoat systems, as a function of cure time and cure temperature and characterization of degradation and embrittlement of weathered acrylic-polyurethane coatings. Comparison of nano thermal analysis with bulk DSC and MDSC is made and its inherent advantages over DSC in analyzing surfaces, is demonstrated.     

Examination of Zinc coatings on Copper substrates by thermal analysis

Copper has excellent thermal conductivity and is mainly applied in electrical and machinery applications. Its main disadvantage is its poor resistance in aggressive environments which can be significantly enforced by the deposition of Zinc coatings. In this study the effect of the deposition time and temperature on the thickness and microstructure of Zinc coatings on Copper substrates by pack cementation process using a DSC apparatus, is investigated. Moreover, the oxidation performance of the coated samples has been evaluated in a high-temperature environment. Oxidation tests were accomplished by thermogravimetric measurements while the coated and oxidized samples were examined with SEM microscopy and XRD diffraction analysis. DSC results revealed that the chemical reactions, which lead to the coating formation, take place up to 300 °C while the coating thickness increases with the duration of the deposition process. The as formed coatings consist of two layers corresponding to different Cu–Zn phases. Finally the coated samples were found to be more resistant when exposed in the aggressive environment, as they begin to oxidize at significant higher temperatures than the uncoated samples. This can mainly attributed to the formation of ZnO on the surface of the coating.     

Study of soils by thermal analysis

The study of soils is very important in the geological and geological engineering researches. A study of ten samples of soils was carried out by thermal analysis, and X-Ray Fluorescence Spectrometry to understand soil evolution in Angra dos Reis region, Rio de Janeiro State, Brazil. The sample collection sites were chosen based on geological characteristics, the soil layer thickness, the soil composition pattern, and whether or not it was moved either by erosion or by gravitational shifts. Because of the humid tropical climatic condition, natural soils tend to show great thickness of weathered mantles with formation of saprolites and saprolite soils. Kaolinite is an important secondary mineral which can be formed from many different minerals, like k-mica and k-feldspar and can be weathered to gibbsite. The results from TG/DTG and DTA indicated which soils had more weathering, and the same results were obtained by XRF, when silica/aluminum ratios from samples are compared with thermal analysis results.     

Transport properties and microstructure changes of alumina coatings characterized by emanation thermal analysis

Emanation thermal analysis was used to characterize the thermal behaviour of alumina coatings as deposited on EUROFER 97 steel surface by filtered vacuum arc technique. Temperature ranges of the healing of cracks and structure irregularities observed by SEM were determined from the ETA results. Transport properties of the alumina coatings were assessed from the ETA results by the evaluation of radon diffusion parameters in the temperature range from 50 to 300°C. Healing microstructure irregularities of the alumina coatings can be expected in the range 300–700°C as indicated by the decrease of the radon release rate. From the ETA results it followed that the onset of healing the cracks observed by the SEM on the surface of one alumina coating sample can be expected at 430°C. Dedicated to Dr. K. Habersberger, Past-Chairman of the thermal analysis working group of the Czech Chemcial Society, at the occasion of his 75^th birthday     

Determination of mercury in crude oil by in-situ thermal decomposition using a simple lab built system

A simple system based on thermal decomposition for the one step determination of mercury has been built. This system was applied to the analysis of crude oil and related products. Samples were directly introduced into the system without the use of chemicals and digestion procedures. After 4 min, matrices and mercury compounds were decomposed, and elemental mercury was collected on a gold sand trap, and then detected by atomic fluorescence spectroscopy (AFS). In principle, any sample can be analyzed by this method provided the sample can be introduced into the system quantitatively. The method detection limit was approximately 0.2 ng/g for 0.04 g of crude oil introduced to the system. Various other samples including, biological, environmental, and general merchandise have been analyzed. Results obtained have been compared with established traditional methods including radiochemical neutron activation analysis (RNAA). Good agreement of results between methods was found. Recoveries were close to 100% for certified reference materials. Results were independent of mercury species and sample types.     

Application of thermal analysis for investigations of polymer powders for coatings

Polypropylene coatings obtained by the fluidized bed method were investigated. It was proved that the application of thermal analysis methods for their characterization gave many useful data, as a consequence of the similar conditions of thermal measurements and plastics powder processing. Significant correlations were found between the thermal properties and the standard coating poperties.

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Zusammenfassung Durch Fluidisationsverfahren erhaltene Polypropylenbeschichtungen wurden untersucht. Es wurde festgestellt, daß infolge der ähnlichen Bedingungen von thermischen Messungen und Plastpulverisierungsverfahren die Anwendung von thermischen Untersuchungsmethoden zu deren Charakterisierung viele nützliche Angaben liefern. Es konnten eindeutige Beziehungen zwischen thermischen Eigenschaften und Standardbeschichtigungseigenschaften gefunden werden.

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Thermal analysis of monument patina containing hydrated calcium oxalates

This work describes the thermal transformation of patina samples formed on the surface of dolomitic rocks used to build the Romanesque Torme's Church (Burgos, Spain). Analyses were performed using a combination of high-temperature XRD, simultaneous TG/DTA and gas mass spectrometry. The XRD analysis revealed the presence of hydrated calcium oxalates. The following three steps were proposed for the thermal transformation of the raw material: dehydration of weddellite/whewellite to form calcium oxalate, transformation of calcium oxalate to calcium carbonate, and formation of calcium oxide produced via decomposition of the calcite. DTA/TG and mass spectrometry analyses confirmed this mechanism. In addition, a high proportion of organic compounds was detected and was possibly formed via degradation of products applied for the building's conservation by the action of microorganisms attack. Mass spectrometry analysis revealed CO (and CO₂) gas evolved during the transformation of CaC₂O₄ to CaCO₃. The CO₂ gas also appears at 765 °C due to the decomposition of calcium carbonate, and it appears over a large range of temperatures due to the decomposition of organic compounds. The TG analyses performed in a CO₂ atmosphere were used to determine the percentages of Ca and Mg contained in dolomite, and the calcium carbonate formed by oxalate decomposition. DRIFTS and mass spectrometry results revealed the presence of several aliphatic and/or aromatic compounds containing CO groups.     

Study of the trivalent elements polyphosphates by thermal analysis

Mechanisms of formation of polyphosphates Me^III(PO₃)₃, where M ^III=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc, Fe, Ga, Al and Cr has been simulated by thermal analysis technique. Me^III oxides and ammonium dibasic phosphate (NH₄)₂HPO₄ were used as starting materials. For M ^III=La-Lu, Y and Fe three main stages were observed: 1. elimination of water and ammonia leading to the formation of ammonium tripolyphosphate (NH₄)₅P₃O₁₀; 2. reaction of the latter with Me₂^IIIO₃ and formation of acidic polyphosphates Me^IIIH₂P₃O₁₀ or their isomers Me^III(PO₃)₃·H₂O; 3. final loss of water and formation of Me^III(PO₃)₃. For Me ^III=Sc and Ga the second stage is prolonged and the polyphosphates form at higher temperatures. Aluminum and chromium polyphosphates are unstable. It is suggested that thermal behavior of the compounds is determined by Me^III ionic radii.     

Study of Na-A molecular sieve degeneration by thermal analysis

The degenerations on heat treatment and the thermal stabilities of Na-A molecular sieve zeolites of different crystallinities were studied by thermal analysis. The degenerations of the sieves were computed from the decreases of the zeolitic water content. The thermal stabilities were determined from the commencement of the exothermic peaks. Heating at 600 causes considerable degeneration of these sieves. The degeneration and thermal stability depend on the crystallinity of the sieve. Poorly-crystalline sieves are degenerated to a greater extent than well-crystaline ones. The thermal stabilities on poorly-crystalline sieves also decrease during heating at 600.

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Zusammenfassung Die infolge der WÄrmebehandlung auftretende Degenerierung und die HietzebestÄndigkeit von Na-A Molekularsiebzeolithen verschiedener KristallinitÄt wurden durch Thermoanalyse untersucht. Die Degenerierung der Siebe wurde an der Abnahme des Zeolithwassergehaltes gemessen. Die HitzebestÄndigkeit. wurde aus dem Anfang des exothermen Peaks abgeleitet. Aufheizen auf 600 verursacht eine bedeutende Degenerierung der Siebe. Degenerierung und HitzestabilitÄt hÄngen von der KristallinitÄt der Substanzen ab. Wenig kristalline Siebe werden in höherem Ma\e degeneriert als hochkristalline. Die HitzebestÄndigkeit wenig kristalliner Spezies wird durch Aufheizen auf 600 ebenfalls herabgesetzt.

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Résumé On a étudié, par analyse thermique, la dégénération causée par traitement thermique ainsi que la stabilité thermique de tamis moléculaires aux zéolithes Na-A de cristallinité différente. On a mesuré la dégénération des tamis à partir de la diminution de la teneur en eau zéolithique. On a déterminé la stabilité thermique à partir du commencement du pic exothermique. Le chauffage à 600 cause une dégénération considérable des tamis. La dégé nération et la stabilité thermique dépendent de la cristallinité des tamis. Des tamis à faible cristallinité dégénèrent plus fortement que ceux à haute cristallinité. La stabilité thermique des tamis à faible cristallinité diminue également lors du chauffage à 600.

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The authors thank Mr. G. C. Bhattacharyya and Mr. A. A. Naqvi for their help in X-ray analysis.     

TG-MS and TG-FTIR applied for an unambiguous thermal analysis of intumescent coatings

Thermogravimetry (TG), thermogravimetry coupled with mass spectroscopy (TG-MS) and thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR) were used to characterise the thermo-oxidative behaviour of two intumescent coating materials. The temperature dependence, the corresponding volatile products and the amount of residue of the different processes were determined. Using both TG-MS and TG-FTIR results in an unambiguous interpretation of the volatile products. Characteristics such as the influence of endothermic reactions, the release of non-flammable gases, the dehydrogenation enhancing the char formation and the stability of the cellular char were discussed in detail. It was demonstrated, that TG, TG-MS and TG-FTIR are powerful methods to investigate mechanisms in intumescent coatings and that they are suitable methods in respect to quality assurance and unambiguous identification of such materials. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study of a Brazilian spent catalyst as cement aggregate by thermal and mechanical analysis

Fluidized catalytic cracking units of refineries normally use zeolite catalysts to treat heavy oil fractions. This catalyst is regenerated continuously, but due to the reduction of its activity during the process, it is partially substituted by a new catalyst make-up. The spent residue has a high content of silicon and aluminum oxides and usually presents pozzolanic properties. This paper presents the study of a Brazilian spent catalyst, which is being tested as a pozzolanic aggregate in partial substitution to cement. Pastes were prepared with 15, 20 and 25% in substitution to cement mass and analyzed after 28 days of hydration. Hydrated paste samples were analyzed by simultaneous thermogravimetry and differential thermal analysis, to quantify the calcium hydroxide consumption, as well as the content of other main hydrated cement phases. Compressive strength analysis was also performed after 28 days of hydration. Although, as spent catalyst content is increased, the pozzolanic activity is confirmed by the increase of calcium hydroxide consumption on cement mass basis, unlikely to other studied spent FCC catalysts, tested for the same purpose, the compressive strength of respective paste specimens decreases, due to the increase of other hydrated phases formation.     

Study of phenolic resin/EVA blends by thermal analysis

The properties of polymeric blends originate from the synergistic association of their components. In this investigation, phenolic resins obtained by the reaction of cashew-nut shell liquid (CNSL) and aldehyde are used in several applications. Mixtures of CNSL with industrial reject ethylene-co-vinyl acetate (EVA reject) were prepared with an EVA reject content up to 70%. The thermal compatibility and stability were evaluated by means of thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). For blends containing a high percentage of EVA reject, the TG curves clearly show two decomposition stages, one at 350C and the other at 450C (onset 467C). The DIG curves of the blend containing 70% CNSL exhibit decomposition at 240C. The DSC curves show that the samples containing a high percentage of EVA reject are incompatible, withT _g values around –30C.The authors would like to thank PETROBRAS/CENPES/DIQUIM for the NMR facilities and thermal measurements.     

Contribution to the analytical characterization of coatings produced by thermal spraying

This paper reports on the use of Auger electron spectroscopy (AES)/ depth profile analysis for the investigation of plasma-sprayed coatings. Prior to spraying the St 37 substrates are heated to 300 °C or 500 °C for ceramic or metallic layers, respectively. Studies of the starting materials and of the interfaces are important if the adhesion mechanism is to be understood. Therefore the initial components—the unheated and heated substrates and the powder particles NiCrAl, Al₂O₃ and ZrO₂-7.25Y₂O₃—are analyzed. Depth profiles obtained from two coatings St 37/NiCrAl and St 37/Al₂O₃ show the influence of plasmaspraying on substrate surfaces and sprayed particles. Plasma-spraying mainly causes a decrease of superficial carbon contamination for both coating layers. In the case of St 37/NiCrAl incorporation of carbon in the sprayed layer is observed. The whole layer is almost completely oxidized except for some areas where substrate and particle material are present. It is assumed that these areas are identical with so-called adherence zones.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Evaluation of a glycerol derived biofuel by thermal analysis

This work describes thermal analysis evaluation of a glycerol derived compound (fatty acid esters of (2,2-dimethyl-1,3-dioxolan-4-yl) methanol) developed to work as a biofuel. Mixtures of these ketal–glyceryl esters with fatty acid methyl esters typical of soybean biodiesel were prepared and evaluated in relation to biodiesel critical thermal properties such as temperature of crystallization, thermal stability and volatilization measured by differential scanning calorimetry and thermogravimetric analysis. The volatility of the products containing fatty acid methyl esters and (2,2-dimethyl-1,3-dioxolan-4-yl) methyl esters could be predicted by thermogravimetric analyses conducted in nitrogen that avoided time consuming distillation and greatly reduced material expenditure.     

Hydration of Portland cement with alkanolamines by thermal analysis

Four types of alkanolamines (i.e., traditional alkanolamines represented by TEA and TIPA and new alkanolamines represented by DEIPA and EDIPA) were added to Portland cement as chemical additives, and their effects on the cement properties and hydration process were investigated. An isothermal calorimeter was used to track the hydration heat flow of the cement pastes with or without alkanolamines. Thermogravimetric analyses were performed to measure the degree of hydration over the course of 28 days. In addition, X-ray diffraction, MIP analysis and SEM were used as auxiliary tests. The results indicated that alkanolamines improved the compressive strength of the cement mortars. It was found that TEA increased the rate of the second hydration of C₃A, and TIPA accelerated the hydration of C₄AF. DEIPA and EDIPA promoted the hydration of both the aluminum and ferrite phases as well as catalyzed the conversion of AFt to the AFm phase. By contrast, the new alkanolamines represented by DEIPA and EDIPA expressed more superior properties.     

Study of water in Ca-montmorillonite by thermal analysis and positron annihilation lifetime spectroscopy

Journal of Thermal Analysis and Calorimetry - The aim of this study is to characterize adsorbed liquid in montmorillonite structure for different levels of adsorption by both thermoanalytical and...     

Study of the combustion of a fire retardant coating by thermal analysis and different complementary techniques

An intumescent fire retardant coating can effectively control fire spread and damage. Its dual purpose is to confine the surface spread of flame to the boundaries of an already established fire, and to retard the penetration of heat and flame to and through the coated surface. Our composition expanded and provided an insulation layer between the flame source and the combustion substrate, and liberated a quantity of primarily non-flammable decomposition products which tended to extinguish the flame. The main ingredients of the coating were cellulose acetate butyrate and HMDI (Desmodur N) for Polyurethane, and Chlorowax-70 (chlorinated paraffins) as fire retardant component. This fire retardant coating was applied to wood panels, and tested in a 2-foot tunnel, its flame spread rating being measured. The effects of three parameters of interest were investigated: the type of wood used, the percentage of Chlorowax, and the coating thickness. It was found of interest to study the oxidation of the coating using different techniques, e.g. flash pyrolysis under oxygen and GC/MS for analysis of the decomposed products. Combustion studies of the coating were also conducted using DSC and thermogravimetry, either with the scanning mode or under isothermal conditions. Comparisons were made between the results obtained from pyrolysis and combustion.

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Zusammenfassung Ein schwellender feuerhemmender Überzug kann Ausbreitung und Schäden von Feuer wirksam einschränken und wird zwei Zwecken gerecht: Verhinderung der Ausbreitung von ausgebrochenem Feuer und Schutz der überzogenen Oberfläche vor Hitze- und direkter Flammeneinwirkung. Die beschriebene Komposition quillt und bildet eine Isolationsschicht zwischen der Flammenquelle und dem brennbaren Material, liefert zugleich aber auch eine gewisse Menge von nichtbrennbaren, die Flamme erstickenden primären Zersetzungsprodukten. Die Hauptbestandteile des Überzugs sind Celluloseacetat und -butyrat und HMDI (Desmodur N) für Polyurethan sowie Chlorowax-70 (chlorierte Paraffine) als feuerhemmende Komponente. Dieser feuerhemmende Überzug wurde auf Holzplatten aufgebracht und in einem 2ft-Tunnel getestet, wobei die Flammenausbreitungsgeschwindigkeit gemessen wurde. Der Einfluß von drei interessierenden Parametern wurde untersucht: Typ des benutzten Holzes, Anteil von Chlorowax und Überzugsschichtdicke. Es erwies sich als interessant, die Oxydation des Überzugmaterials mit verschiedenen Techniken zu untersuchen, z.B. durch Schnellpyrolyse und Analyse der Zersetzungsprodukte mittels GC/MS. Verbrennungsuntersuchungen des Überzugmaterials wurden auch mittels DSC und Thermogravimetrie entweder nach der scanning-Arbeitsweise oder unter isothermen Bedingungen ausgeführt. Die bei Pyrolyse und Verbrennung erhaltenen Ergebnisse werden miteinander verglichen.

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