FTIR, a powerful technique in organic coatings failure diagnosis

FTIR spectrometry (Fourier Transform Infrared) is an instrumental technique of analysis that presents significant advantages on the dispersive traditional system, such as the increase of the relation signal-noise, the capacity of getting absorption spectra of low energy and therefore, bands of absorption of weak intensity. This technique is widely used in the study of resin characterization and evaluation of polymeric materials as well as degradation when polymers and coatings are exposed to various conditions of service, or still in the analysis and diagnosis of defects that occur during the application or production process. Techniques connected to the FTIR have appeared such as the photoacoustic (PAS-FTIR), the microscopy (MCT-FTIR) and the attenuated total reflectance (ATR), which allows to analysis of weekly transparent and dark samples without removal of coatings from the substrates. The choice of the technique to use depends on the morphology of the surfaces to analyze and the type of failure (lack of adhesion, contamination, aging degradation, etc). This work illustrates the application of FTIR and associated techniques to identify causes of diverse types of defects in applied organic coatings on polymeric materials

Quaternary evolution of Vilaric.;a Graben (Trás-os-Montes, NE Portugal)

[Abstract] In Portugal, the Douro River has a first large bend, leaving it's E-W general orientation after the Spanish border and near the Coa River mouth; another infiection occurs in Pocinho, where the Douro River fills the Vilari\a tectonic depression and receives the water from the Sabor River and the Vilari\a stream. The Vilari\a stream fills a NNE-SSW fiat valley situated between Serra de Bornes and the Sabor River. Quaternary evolution of this sector of the Hesperic Massif is recognized by the valley morphology and sediments, the Serra de Bornes' uplift and tectonic displacement (horizontal and vertical) ofgranites and Paleozoic series. All these evidences are associated with the Bragan\a-Vilari\a-Manteigas NNE-SSW tectonic accident, where more sediments are being studied. Many of these sediments have in common an alluvial fan origin and ages since Paleogene are proposed. Vilari\adepositsand Pleistocene Douro terraces present identical characteristics in geomorphological position and sorne sedimentologic features like reddish color and kaolinite-illite-smectite clay association; these similar characteristics justify a Quaternary age proposal for the Vilari\adeposits. The variation ofother sedimentological characteristics along the valley suggests the presence of several alluvial fans

A CORROSÃO E A PROTEÇÃO DOS MATERIAIS NOS SISTEMAS SOLARES TÉRMICOS SEM E COM CONCENTRAÇÃO

Comunicação sobre a corrosão e a proteção dos materiais nos sistemas solares térmicos sem e com concentração no V Encontro do Dia Mundial da Sensibilização para a Corrosão: Energias Renováveis: Materiais e Durabilidade, Ordem dos Engenheiros, Lisboa, Portugal, 24 Abril, 201

FTIR, a powerful technique in organic coatings failure diagnosis

FTIR spectrometry (Fourier Transform Infrared) is an instrumental technique of analysis that presents significant advantages on the dispersive traditional system, such as the increase of the relation signalnoise, the capacity of getting absorption spectra of low energy and therefore, bands of absorption of weak intensity. This technique is widely used in study, resin characterization and evaluation of polymeric materials as well as of its degradation when exposed to the most varied conditions of service, or still in the analysis and diagnosis of defects that occur during the application or production process. Techniques connected to the FTIR had more recently appeared as the photoacoustic (PAS-FTIR), the microscopy (MCT-FTIR) and the attenuated total reflectance (ATR), which allow to analyze weekly transparent and dark samples without removal of coatings from the substrates. The choice of the technique to use depends on the morphology of the surfaces to analyze and the type of failure in cause (lack of adhesion, contamination, aging degradation, etc). In this work the application of FTIR and techniques associates to the identification of the causes that had originated diverse types of defect in applied organic coatings on polymeric materials is presented. Key words: FTIR, Organic Coatings, Failure Diagnosi

Assessment of durability of solar absorbers : performance criterion

ABSTRACT: Solar fraction, Fs, defined as the ratio between the delivered energy from a solar domestic hot water (DHW) system and the load (thermal energy necessary to satisfy domestic water heating needs), is widely accepted as performance indicator for this type of systems. Considering solar absorptance αs and thermal emittance εt as the most relevant characteristics of solar absorbers, the relation between the depreciation of these optical properties and depreciation of Fs was used by Hollands et al (1992) to define a performance criterion (PC) for assessment of long-term behavior and service life of selective solar absorbers. The PC was established mainly for solar DHW systems working with solar fractions lower than 50%. In this work, systems working with solar fractions higher than 50%, in climates of south of Europe, are considered and the suitability of solar fraction as performance indicator to develop an adequate PC is studied. As a first step simulations of thermal performance of systems using an in-house software were performed for a reduction of 5% and 10% of Fs. In ISO 22975-3, solar fraction Fs degradation must be lower than 5% to guarantee 25 years of service life for DHW system. The results showed that the parameters obtained to define the PC were incoherent considering solar fractions higher than 50%. In a second step, supplied energy was considered as performance indicator and using similar methodology as Hollands et al (1992), but using as performance indicator energy supplied by the solar system, the PC for systems working with solar fractions higher than 50%, in climates of south of Europe, was establish. The results showed that this is not significantly different from the PC considered in ISO 22975-3.info:eu-repo/semantics/acceptedVersio

Molten nitrate salts containing lithium as thermal energy storage media : a short review

ABSTRACT: Energy storage plays a crucial role in the development and progress of renewable energy sources. In the case of thermal energy, storage has been a step ahead since storage solutions already exist, unlike other conversion energy technologies. In this sense, the utilization of molten salts, mainly composed of mixtures of alkali/alkaline earth metals, in nitrate forms (sometimes also with nitrite), have been proposed and successfully applied. Molten salts have recognized advantages over other solutions namely in what concerns simultaneous use as heat transfer fluids and as storage media. Commercial utilization of molten salts has been tested essentially with the Na/K salt mixtures. Introduction of lithium nitrate in these formulation has been proposed, since can allow decreasing the melting point of the mixtures, thus providing safety concerning the risks of freezing in the tubes or tanks of the storage plant. This paper provides a short review on the utilization of lithium in molten salt mixtures used for thermal energy storage. Physical, chemical and thermal properties, as well as stability and decomposition issues are evaluated. Corrosion of stainless steels in contact with the salts is another crucial question that is also addressed.info:eu-repo/semantics/publishedVersio

Thermally modified wood exposed to different weathering conditions: A review

ReviewOutdoor wood applications are exposed to several different biotic and abiotic factors, and for that reason, they require protection to increase their service life. Several technologies of wood protection are already commercialized. One of these technologies is thermal modification, which refers to the structural, mechanical, and chemical transformations occurring in the lignocellulosic material when gradually heated up to specific temperature ranges. In the past few years, several researchers have undertaken weathering resistance evaluations on different wood species. Some cases have considered natural exposure in different countries with different climatic conditions, while others focused on artificial exposure under UV and xenon radiation tests. Most works evaluated the weathering effects on the chemical, mechanical and physical, and anatomical shifts compared to the original characteristics of the material. This review has established a considerable lack of studies in the bibliography focusing on abiotic factors, such as the industrial and maritime environment, or even isolated climatic factors such as salt spray (simulating maritime environments) or pollutant gases (simulating industrial environments). This lack of information can be an opportunity for future work. It could help to understand if thermally modified wood is or is not sensitive to pollutant gases or salinity, or to a combination of both. By knowing the degradation mechanisms caused by these factors, it will be possible to study other forms of protectioninfo:eu-repo/semantics/publishedVersio

Breve história das tintas antivegetativas

Neste trabalho, os autores apresentam uma panorâmica geral sobre as tintas antivegetativas. Após a conveniente localização destas tintas no esquema de protecção anticorrosiva das obras vivas dos navios e/ ou outras estruturas móveis, fazem uma síntese dos principais tipos de produtos antivegetativos usados ao longo dos tempos, até aos nossos dias. Complementarmente, sistematizam as principais tipologias dos organismos vivos que se fixam nas obras vivas das embarcações e referem alguns tipos de fauna e flora predominantes em duas regiões da Ibero-América. Abordam também, ainda que sumariamente, os principais mecanismos básicos de funcionamento dos diferentes tipos de tintas antivegetativas. Finalmente, referem algumas das principais linhas de investigação actualmente em curso, no domínio da luta contra a fixação dos organismos marinhos nos cascos dos navio

High-temperatures corrosion of AISI 316L and AISI 430 steels in dynamic conditions with molten solar salt

ABSTRACT: Potassium nitrate and sodium nitrate in mixing proportion of KNO3–NaNO3 40-60 wt% (also called solar salt) has been successfully used for over a decade as a heat storage medium for concentrated solar power plants. At temperatures of 550 ºC, reached in state-of-the-art solar tower systems, corrosion of metallic components in contact with solar salt can become an issue and has caused leaks and plant shut-downs in recently built tower projects. While the corrosion rates of several materials have been determined for different temperatures in static molten salt immersion experiments, there is a lack of corrosion data for dynamic inservice conditions. Fluid dynamics and scale-up are two factors that can influence the corrosion phenomena. In this work, corrosion studies were carried out on austenitic stainless steel (SS) (AISI 316L) and ferritic steel (AISI 430) under dynamic conditions, with long-term immersion in solar salt, on a pilot scale. It was found that AISI 316L steel forming more adherent oxides, presented a significantly lower corrosion rate than the AISI 430 steel, due to the formation of a protective FeCr2O4 layer, making it less susceptible to corrosion. The measured corrosion rates are presented and compared to static corrosion tests.info:eu-repo/semantics/publishedVersio

Durability of CSP Materials

Durability of CSP materials. Presentation for 4th SYMPOSIUM IPES by Teresa Diamantino