Στην εργασία αυτή μελετήθηκε η μεταβολή της ειδικής ηλεκτρικής αγωγιμότητας συναρτήσει της θερμοκρασίας για την πολυπυρρόλη, την πολυανιλίνη καθώς και συνθέτων αυτών εμπλουτισμένων με οξείδιο του ψευδαργύρου και ατμούς μεταλλικού ιωδίου με σκοπό την εφαρμογή των παραπάνω υλικών ως υποστρώματα σε φωτοβολταϊκές κυψελίδες (solar cells). Τα παραπάνω υλικά ανήκουν στην κατηγορία των οργανικών ημιαγωγών και αποτελούν τη λεγόμενη "τέταρτη γενιά" πολυμερών. / In this work the thermal aging of conducting polyaniline and polypyrrole and their blends with ZnO : (PPy/ZnO (x% w/w) with x =10, 20, 30, 40),PANI/ZnO (20% w/w) and iodine has been investigated for the application of these materials as substrates in photovoltaic cells. Today, research is focused on the organic solar cells, in which the electrical current flow is due to molecules, which play the role of donors or acceptors of electrical charge. Organic PV cells have the advantages of easy construction, low cost and they are friendly to the environment. Indium tin oxide is used as anode in organic PVs, which is characterized by high concentration of charge carriers and is used for the injection of positive charge carriers (holes) in the organic active layer. For all the samples conductivity followed one of the models: 1. FIT (Fluctuation Induced Tunneling), in the case that we have a granular metal structure, in which conductive grains are separated by insulating barriers. These insulating barriers are narrow enough for the carriers to tunnel through small areas where the grains are closest together and the conductivity is dominated by the thermal fluctuations of the carriers in these areas. The relationship σ=f(T) is given by σ=σ0 exp[-T1/T0+T]. From T1 and T0 the distance s between the grains can be determined. In this work the FIT model applied to the sample of pure polypyrrole throughout the duration of thermal degradation. 2. CELT (Charging Energy Limited Tunneling), in the case that we have a granular metal structure, through which the carriers move by tunneling effect. T0 is related directly to the ratio s/d, where s is the main separation and d is the mean diameter of the grains and can give informations about the shrinking of the grains during aging. The relationship between σ and T is given by: σ=σ0 exp[-(Τ0/Τ)γ] where σ0 and T0 are indepedent factors of the temperature and 0 < γ < 0,25. In this work the CELT model applied for the samples of pure polyaniline, PPy/ZnO (10% w/w), PPy/ZnO (20 %w/w), PANI/ZnO (20% w/w) and PPy/I throughout the duration of thermal degradation. 3. Mott (Variable range hopping model), in the case of heterogeneous structures of amorphous materials. The conductivity takes place by thermally activated electron hopping between localized states near Fermi energy. The localization is due to the randomly distributed atoms or molecules in the material. The relationship describing the change in conductivity with T is similar to that of the CELT model, with the exponent γ is roughly equal to 0,25. In this work the Mott model applied for the samples PPy/ZnO(40% w/w) and PPy/I (sublimation with iodine vapour for 24 h). The degreasing of conductivity σ, with thermal aging time t for a substance with a granular metal structure follows the law: σ=σαρχ exp[-(t/τ)0,5] where τ is the time which characterizes the aging. All our composites followed this relation, ensuring a granular metal structure. It also became apparent that heating greatly reduces the electrical conductivity of our composites. The thermal degradation of PANI at room temperature (300K) gives τ = (350 ± 50) h, though at 120 0C PANI gives τ = (18 ± 4) h, indicating a much faster degradation as it is expected. The characteristic parameter τ has been calculated for all the materials used in this work.

No description available.

Cette thèse de doctorat s’intéresse à la fatigue des élastomères, et plus particulièrement des caoutchoucs nitrile hydrogénés (sigle HNBR en anglais). Les HNBR sont des élastomères de haute performance,classiquement utilisés pour des applications industrielles à haute température où une bonne résistance chimique aux hydrocarbures est également requise.La thèse est divisée en trois parties principales.En premier lieu, des améliorations majeures pour les expériences de durée de vie en fatigue des élastomères sont proposées. Une approche expérimentale originale permettant le pilotage des essais en contrainte vraie est détaillée.Grâce à cette méthode, la première « vraie »courbe de Wöhler (contrainte vraie en fonction du nombre de cycles) pour des élastomères est tracée. Ensuite, des outils statistiques, issus de la recherche médicale, permettent une analyse probabiliste des résultats présentant une grande dispersion et des durées de vie censurées.Dans un second temps, ces nouveaux outils sont utilisés pour étudier l'effet de la formulation chimique – les taux d’acrylonitrile et d'hydrogénation notamment - sur la résistance en fatigue du HNBR à 120 oC. Ces résultats sont complétés par des expériences de propagation de fissure de fatigue et par une analyse de l'endommagement. Finalement, l'influence du vieillissement thermique sur la résistance en fatigue du HNBR est étudiée ; deux nouveaux essais sont développés : des essais simultanés de vieillissement et de fatigue, et des expériences de fatigue sur des échantillons préalablement vieillis.De plus, la cristallisation sous tension dans le HNBR est pour la première fois étudiée de manière quantitative / The present PhD thesis is devoted to investigation of fatigue in elastomers, andmore particularly of carbon black-filled hydrogenated nitrile butadiene rubber (HNBR).HNBR is a high performance elastomer classically used for high temperature industrial applications, where high resistance to industrial solvents is also required.The thesis is divided into three main parts.First, major improvements of testing procedures utilized in fatigue life testing ofelastomers are proposed. An original method to prescribe the true stress throughout fatigue experiments is developed; it permits to plot the first “true” Wöhler curve, i.e. true stress vs.number of cycles, for elastomers. Then,statistical tools, widely applied in medical research, are adopted for a comprehensive probabilistic analysis of fatigue life results that exhibit high scatter and censored lifetimes.Second, these novel tools are used to investigate the effect of chemical formulation -acrylonitrile content, percent hydrogenation,and of a composite blend - on fatigue resistance of HNBR at the service temperature of 120 oC. In addition to these fatigue life tests,fatigue crack propagation experiments and microscopic fatigue damage analysis are carried out. Third, the influence of thermal aging on fatigue performances of HNBR is investigated.To this end, two additional fatigue life tests are carried out: simultaneous aging and fatigue experiments, and fatigue experiments on preaged samples.Additionally, strain-induced crystallization in HNBR is studied; for the first time, quantitative relationships between crystallization, strain,and stress are established for unfilled HNBR blends.

Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Convencionalmente, metais nobres são empregados como metais ativos em catalisadores automotivos, mas o uso de cobre vem sendo estudado pelo fato de promover sítios ativos para adsorção química e redução de NOx. Diante deste contexto, esta dissertação visa testar novas formulações de catalisadores, com foco em seu desempenho na reação de redução do NO pelo CO e sua seletividade a N2. Foram avaliados o método de adição de cobre no preparo e os teores de cobre utilizados na preparação. Os métodos de adição utilizados foram impregnação a seco (IS), reação em estado sólido (RS) e coprecipitação (CO). Os teores de cobre estudados ficaram entre 0,36 e 6,9% (m/m). Além disso, foi estudado o impacto no desempenho do catalisador após envelhecimento térmico a 950C por 12h. Foram empregadas as seguintes técnicas de caracterização textural e físico-química como espectrometria de absorção atômica, fisissorção de N2, difração de raios X, espectroscopia Raman e redução a temperatura programada. Os catalisadores também foram avaliados na reação de redução do NO pelo CO. A análise textural indicou que o método de coprecipitação levou a características texturais diferentes dos outros catalisadores. Análises de DRX mostraram a formação de CuO cristalino para teores iguais ou superiores a 3,3% (m/m) de cobre. As análises de Redução a Temperatura Programada (RTP) indicaram que ocorreu uma forte interação na interface entre o suporte e as espécies de cobre dispersas, acompanhada da diminuição da temperatura de redução do CuO e da redução parcial da céria em temperaturas mais baixas. Os testes catalíticos mostraram um melhor desempenho dos catalisadores (IS) que apresentaram conversões mais elevadas em menores temperaturas. Com relação ao envelhecimento, observou-se uma diminuição significativa da eficiência dos catalisadores. Uma comparação com catalisadores à base de metal nobre mostrou um bom desempenho dos catalisadores à base de cobre, com a vantagem destes apresentarem emissão de N2O restrita a baixas temperaturas / Conventionally, noble metals are used as active metals in automotive catalytic converters, but the use of copper has been studied because copper promote active sites for chemical adsorption and reduction of NOx. Thus, this work aims to test new formulations of automotive catalysts, focusing on their performance in catalytic reduction of NO by CO and its selectivity to N2. The method of copper addition and the copper contents used in the preparation were evaluated. The addition methods used were dry impregnation (IS), solid state reaction (RS) and coprecipitation (CO). The copper contents studied were between 0,36 e 6,9 wt%. In addition, the impact on catalyst performance after thermal aging at 950 C for 12h was also studied. Textural and physico-chemical caracterization techniques were employed, such as atomic absorption spectrometry, N2 physisorption, X-ray diffraction, Raman spectroscopy and temperature programmed reduction. Catalysts were evaluated in the reduction reaction of NO by CO. The textural analysis indicated that addition of copper by the coprecipitation method led to textural characteristics different from the other catalysts. XRD analysis showed the formation of crystalline CuO for contents equal to or greater than 3,3 wt% of copper. TPR analysis indicated that there was a strong interaction at the interface between the substrate and the copper species dispersed together with the lowering of the temperature reduction of CuO and the partial reduction of ceria at lower temperatures. The catalytic activity results showed a better performance of the (IS) catalysts, which showed higher conversions at lower temperatures. Concerning the aging process, there was a significant decrease in the efficiency of the catalysts. A comparison with catalysts doped with noble metal showed good performance of the catalysts doped with copper, with the advantage of these presenting N2O emission restricted to low temperatures

Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Convencionalmente, metais nobres são empregados como metais ativos em catalisadores automotivos, mas o uso de cobre vem sendo estudado pelo fato de promover sítios ativos para adsorção química e redução de NOx. Diante deste contexto, esta dissertação visa testar novas formulações de catalisadores, com foco em seu desempenho na reação de redução do NO pelo CO e sua seletividade a N2. Foram avaliados o método de adição de cobre no preparo e os teores de cobre utilizados na preparação. Os métodos de adição utilizados foram impregnação a seco (IS), reação em estado sólido (RS) e coprecipitação (CO). Os teores de cobre estudados ficaram entre 0,36 e 6,9% (m/m). Além disso, foi estudado o impacto no desempenho do catalisador após envelhecimento térmico a 950C por 12h. Foram empregadas as seguintes técnicas de caracterização textural e físico-química como espectrometria de absorção atômica, fisissorção de N2, difração de raios X, espectroscopia Raman e redução a temperatura programada. Os catalisadores também foram avaliados na reação de redução do NO pelo CO. A análise textural indicou que o método de coprecipitação levou a características texturais diferentes dos outros catalisadores. Análises de DRX mostraram a formação de CuO cristalino para teores iguais ou superiores a 3,3% (m/m) de cobre. As análises de Redução a Temperatura Programada (RTP) indicaram que ocorreu uma forte interação na interface entre o suporte e as espécies de cobre dispersas, acompanhada da diminuição da temperatura de redução do CuO e da redução parcial da céria em temperaturas mais baixas. Os testes catalíticos mostraram um melhor desempenho dos catalisadores (IS) que apresentaram conversões mais elevadas em menores temperaturas. Com relação ao envelhecimento, observou-se uma diminuição significativa da eficiência dos catalisadores. Uma comparação com catalisadores à base de metal nobre mostrou um bom desempenho dos catalisadores à base de cobre, com a vantagem destes apresentarem emissão de N2O restrita a baixas temperaturas / Conventionally, noble metals are used as active metals in automotive catalytic converters, but the use of copper has been studied because copper promote active sites for chemical adsorption and reduction of NOx. Thus, this work aims to test new formulations of automotive catalysts, focusing on their performance in catalytic reduction of NO by CO and its selectivity to N2. The method of copper addition and the copper contents used in the preparation were evaluated. The addition methods used were dry impregnation (IS), solid state reaction (RS) and coprecipitation (CO). The copper contents studied were between 0,36 e 6,9 wt%. In addition, the impact on catalyst performance after thermal aging at 950 C for 12h was also studied. Textural and physico-chemical caracterization techniques were employed, such as atomic absorption spectrometry, N2 physisorption, X-ray diffraction, Raman spectroscopy and temperature programmed reduction. Catalysts were evaluated in the reduction reaction of NO by CO. The textural analysis indicated that addition of copper by the coprecipitation method led to textural characteristics different from the other catalysts. XRD analysis showed the formation of crystalline CuO for contents equal to or greater than 3,3 wt% of copper. TPR analysis indicated that there was a strong interaction at the interface between the substrate and the copper species dispersed together with the lowering of the temperature reduction of CuO and the partial reduction of ceria at lower temperatures. The catalytic activity results showed a better performance of the (IS) catalysts, which showed higher conversions at lower temperatures. Concerning the aging process, there was a significant decrease in the efficiency of the catalysts. A comparison with catalysts doped with noble metal showed good performance of the catalysts doped with copper, with the advantage of these presenting N2O emission restricted to low temperatures

The aim of this masterś thesis is to investigate properties of lead-free low-temperature solders after termal aging. The theoretical part is focused on various types of lead - free solders, pastes used for the manufacture of electrical circuits by thick-film technology and methods of testing the properties of the soldered joints. The practical part deals with the design and production of test substrates for testing the solder joints formed between the SMD component and the ceramic substrate. Two solder bismuth-containing solder was selected for testing, the SAC solder was selected as the reference. After aging with temperature cycling from -30 ° C to 115 ° C, the data obtained by testing the mechanical strength of the solder joint by the shear test is evaluated.

Element Materials Technology in Linköping is an independent material testing company that performs testing of materials to several big sectors, such as the Swedish Armed Forces and the aerospace industry. There is of great importance to characterize aging of materials to ensure material performance. Element Materials Technology recently invested in a handheld FTIR equipment and it was of interest to see if this equipment might be an additional analysis technique to characterize aging of rubber materials. A nitrile butadiene rubber and two natural rubbers were thermally aged in 50°C and 70°C for six weeks. The hardness of the rubbers increased when the rubbers were thermally aged. The compression set decreased for the aged samples as well as the tensile strength and the elongation at break. An investigation of possible methods for collecting migrated additives on the rubber surface was performed, using two different solvents and a stationary FTIR equipment. More research needs to be performed to exclude the possibility that the solvents affect the material. Universal Attenuated Total Reflectance – Fourier Transform Infrared Spectroscopy, UATR-FTIR onto the rubber surface showed in some cases changes in the spectrums between unaged and aged samples. However, it could not be concluded weather the changes occurred due to migrating additives or due to changes in the backbone polymer. Four interfaces to the handheld FTIR equipment were investigated and an ATR interface gave best results. An analysis method was developed for the handheld FTIR equipment and the spectrums from the handheld FTIR were similar to spectrums from UATR-FTIR (stationary). It could be concluded from Micro Chamber analysis that volatile organic matters were emitted at elevated temperature. Thermogravimetric analysis could detect the relative composition of the rubbers. Further it could be concluded that the mechanical properties were affected by the thermal treatment. This study could however not establish a correlation between FTIR signals and the results seen from the other analysis. The fact that differences could be detected in the FTIR spectrums before and after aging could indicate that the FTIR analysis technique can possibly be used as an analysis method. However, a more thoroughly investigation needs to be performed before using this technique. / Element Materials Technology i Linköping utför materialutredningar åt en mängd olika typer av företag, där en stor sektor är den svenska Försvarsmakten och flygindustrin. Materialutredningar är essentiella för att säkerställa att rätt material används för rätt applikation. Element Materials Technology investerade nyligen i en handhållen FTIR utrustning. Det finns förhoppningar om att den nya utrustningen kan användas som ett komplement för att ålderskarakterisera gummimaterial. Ett nitril-butadien-gummi och två stycken naturgummin var termiskt åldrade i 50°C och 70°C i sex veckor. Hårdheten på provkroppar ökade efter den termiska åldringen. Sättningen, draghållfastheten och töjningen minskade för proverna åldrade i värme. En metod för att samla upp migrerade additiv från gummiytan utvecklades och undersöktes, genom att använda två olika lösningsmedel och en stationär FTIR utrustning. Ytterligare utredningar behöver däremot genomföras för att utesluta ifall de två lösningsmedel påverkar gummimaterialet och inte bara samlar upp additiv från gummiytan. UATR-FTIR visade på skillnader i spektrum mellan icke-åldrade och åldrade gummimaterial. Däremot kunde det inte avgöras om skillnaderna i spektrumen berodde på migration av additiv till gummiytan eller på förändring i huvudpolymeren. Fyra stycken olika tillbehör till den handhållna FTIR utrustningen prövades, där ATR-tillbehöret gav bra spektrum. En analyseringsmetod utvecklades för den handhållna FTIR-utrustningen och spektrum från dessa analyser gav liknande spektrum som spektrum från UATR-FTIR (stationär). Analys med Micro Chamber visade att flyktiga organiska ämnen lämnade gummimaterialet vid förhöjd temperatur. Termogravimetrisk analys, TGA visade förhållandet mellan gummimaterialets komponenter både före och efter åldring. Studien visade också att de mekaniska egenskaperna påverkades av den termiska åldringen. Analysmetoden FTIR kunde detekterad skillnad i spektrum före och efter åldring av gummimaterialen. Studien kunde däremot inte etablera ett samband mellan dessa FTIR-signaler och de övriga analysresultaten. Det kan däremot inte uteslutas att ett sådant samband finns. Ytterligare studier behöver utföras för att undersöka detta.

Le besoin pressant de substitution du plomb dans les alliages de soudure a conduit à une introduction très rapide de nouveaux alliages sans plomb dont la connaissance en termes de comportement n'est pas assez approfondie. En effet, d'autres problématiques sont apparues (l'augmentation de la température du procédé de soudage, trop grand choix disponible dans les alliages alternatifs) alors que les problèmes relatifs aux alliages actuels sont restés sans réponse (le changement incessant de la microstructure des alliages de soudure, la méthodologie empirique prédisant la durée de vie). Tous les paramètres cités ci-dessus modifient la stabilité et la fiabilité des performances spécifiques de l'alliage de soudure et par conséquence, de tout le module électronique.De plus, avec la miniaturisation de l'électronique et les conditions d'environnement de plus en plus sévères, ces obstacles deviennent critiques et les solutions actuelles ne sont plus compatibles. Les demandes de ce marché deviennent donc de plus en plus strictes en termes de prédiction de durée de vie et de contrôle de fiabilité.L'objectif de ce projet est de comprendre et de concevoir une nouvelle formulation d'alliage sans plomb afin de développer une alternative à l'alliage plombé haute température et un alliage pour les applications haute fiabilité et en accord avec les directives gouvernementales. Des approches expérimentales avancées comme la nano-indentation, le suivi de l'évolution de la microstructure par SEM et par EDS mapping, l'étude des effets du vieillissement thermique sur la croissance de la taille des grains avec de la lumière croisée polarisée de microscopie optique etc seront utilisées pour développer un alliage sans plomb qui convienne aux exigences des applications automobile et pipeline / The urgent need for removing lead from solder alloys led to the very fast introduction of lead-free solder alloys without a deep knowledge of their behaviour. As a consequence, additional issues raised (increased thermally induced problems during soldering process, a too wide range of possible available alternative alloy formulations), while problems related to current solder alloys remained unsolved (the constant change of the solder alloy microstructure, empirical predicting lifetime methodology). All the above mentioned issues alter stability and reliability of the application specific performances of the solder alloy, and subsequently of the whole electronic module. These problems become critical and are no longer compatible, as the market goes towards miniaturization and harsh environment conditions. These market trends now require stricter life time prediction and reliability control. Objective of this project is to understand and design a novel lead-free solder formulation to develop a potential alternative to lead-based high temperature melting point solder for high reliability requirements and in accordance with governmental directives. An advanced experimental approach like nanoindentation, microstructure evolution with SEM and EDS mapping, thermal aging effects on continuous grain size growth with cross polarized light of optical microscopy etc. would be implemented to develop doped-SAC lead-free solders for the best-fit to requirements in automotives and pipelines applications

Dans le cadre des applications transports, et plus particulièrement de "l’avion plus électrique", avec une demande toujours plus présente de réduction d’encombrement et de poids, la tendance est à l’intégration de plus en plus poussée des convertisseurs statiques. L’augmentation de leur densité de puissance et celle des contraintes thermiques, induites par l’environnement dans lequel ces structures sont localisées, deviennent de plus en plus critiques. La gestion thermique de ces dispositifs est assurée par des systèmes de refroidissement sur lesquels sont montés les composants semi-conducteurs via un matériau d’interface thermique. Une gestion performante sera obtenue par la diminution de la résistance thermique globale entre les éléments dissipatifs et le milieu ambiant grâce en autre à l’amélioration du système de refroidissement et des propriétés thermiques des matériaux constituant le module. Or cette interface est un point délicat du transfert de chaleur car elle peut représenter plusieurs dizaines de pourcents de la résistance thermique globale. Elle nécessite donc une connaissance approfondie de son comportement aux sollicitations thermiques. Après un état de l’art sur les matériaux d’interfaces thermiques et les méthodes de caractérisation des propriétés thermophysiques des matériaux, nous proposons la mise en œuvre d’outils expérimentaux et mathématiques permettant de suivre l’éventuelle évolution de matériaux d’interfaces utilisés en électronique de puissance au cours d’un vieillissement par cyclage en température. Pour cela, deux méthodes sont présentées. La première repose sur la mesure de la résistance thermique des interfaces en régime stationnaire avec un transfert de chaleur monodimensionnel alors que la seconde, basée sur une caractérisation transitoire thermique d’un système, permet d’en identifier les constantes de temps et le réseau Résistance-Capacité du système testé. Des travaux de simulations numériques ont été menés sur les deux types de bancs expérimentaux, d’un côté pour pouvoir évaluer les pertes thermiques latérales du banc statiques, de l’autre côté pour montrer qu’il est bien possible de détecter une variation de la résistance thermique d’un matériau d’interface par l’analyse de l’impédance thermique. / In the context of transportation applications, and especially the "more electric aircraft", with an ever present demand for space and weight reduction, the trend is to integrate more extensive of static converters. The increase in power density and the thermal stresses induced by the environment in which these structures are located, are becoming increasingly critical. Thermal management of these devices is provided by cooling systems on which are mounted the semiconductor components via a thermal interface material. Effective management will be achieved by reducing the overall thermal resistance between the dissipative elements and the environment by improving the cooling system and thermal properties of the materials constituting the module. However, this interface is a delicate point of heat transfer because it can represent several tens of percent of the circuit total thermal resistance. It therefore requires a thorough knowledge of their behavior in thermal stresses. After a state of the art on the thermal interface materials and methods for characterizing thermophysical properties of materials, we propose the implementation of experimental and mathematical tools to monitor any change of interface materials used in power electronics during aging by temperature cycling. For this, two methods are presented. The first is based on the measurement of the thermal resistance of the interfaces with a steady one-dimensional heat transfer, while the second, based on a characterization of a transient thermal system, allows to identify the time constants and the resistor and capacitor network of the tested system. Numerical simulations were carried out on two types of experimental benches, on one side in order to assess the lateral heat losses from static bench, on the other side to show that it is possible to detect a change in the thermal resistance of a TIM with the analysis of the thermal impedance.

Power and Generator Transformers are important and expensive elements of a power system. Inadvertent failure of Power Transformers would cause long interruption in power supply with consequent loss of reliability and revenue to the supply utilities. The mineral oil impregnated paper, OIP, is an insulation of choice in large power transformers in view of its excellent dielectric and other properties, besides being relatively inexpensive. During the normal working regime of the transformer, the insulation thereof is subjected to various stresses, the more important among them are, electrical, thermal, mechanical and chemical. Each of these stresses, appearing singly, or in combination, would lead to a time variant deterioration in the properties of insulation, called Ageing. This normal and inevitable process of degradation in the several essential properties of the insulation is irreversible, is a non-Markov physico-chemical reaction kinetic process. The speed or the rapidity of insulation deterioration is a very strong function of the magnitude of the stresses and the duration over which they acted. This is further compounded, if the stresses are in synergy. During the processes of ageing, some, or all the vital properties undergo subtle changes, more often, not in step with the duration of time over which the damage has been accumulated. Often, these changes are non monotonic, thus presenting a random or a chaotic picture and understanding the processes leading to eventual failure becomes difficult. But, there is some order in this chaos, in that, the time average of the changes over short intervals of time, seems to indicate some degree of predictability. The status of insulation at any given point in time is assessed by measuring such of those properties as are sensitive to the amount of ageing and comparing it with earlier measurements. This procedure, called the Diagnostic or nondestructive Testing, has been in vogue for some time now. Of the many parameters used as sensitive indices of the dynamics of insulation degradation, temporal changes in temperatures at different locations in the body of the transformer, more precisely, the winding hot spots (HST) and top oil temperature (TOT) are believed to give a fairly accurate indication of the rate of degradation. Further, an accurate estimation of the temperatures would enable to determine the loading limit (loadability) of power transformer. To estimate the temperature rise reasonably accurately, one has to resort to classical mathematical techniques involving formulation and solution of boundary value problem of heat conduction under carefully prescribed boundary conditions. Several complications are encountered in the development of the governing equations for the emergent heat transfer problems. The more important among them are, the inhomogeneous composition of the insulation structure and of the conductor, divergent flow patterns of the oil phase and inordinately varying thermal properties of conductor and insulation. Validation and reconfirmation of the findings of the thermal models can be made using state of the art methods, such as, Artificial Intelligence (AI) techniques, Artificial Neural Network (ANN) and Genetic Algorithm (GA). Over the years, different criteria have been prescribed for the prediction of terminal or end of life (EOL) of equipment from the standpoint of its insulation. But, thus far, no straightforward and unequivocal criterion is forth coming. Calculation of elapsed life in line with the existing methodology, given by IEEE, IEC, introduces unacceptable degrees of uncertainty. It is needless to say that, any conformal procedure proposed in the accurate prediction of EOL, has to be based on a technically feasible and economically viable consideration. A systematic study for understanding the dynamical nature of ageing in transformers in actual service is precluded for reasons very well known. Laboratory experiments on prototypes or pro-rated units fabricated based on similarity studies, are performed under controlled conditions and at accelerated stress levels to reduce experimental time. The results thereof can then be judiciously extrapolated to normal operating conditions and for full size equipment. The terms of reference of the present work are as follows; 1. Computation of TOT and HST Theoretical model based on Boundary Value Problem of Heat Conduction Application of AI Techniques 2. Experimental Investigation for estimating the Elapsed Life of transformers Based on the experimental investigation a semi-empirical expression has been developed to estimate the loss of life of power and station transformer by analyzing gas content and furfural dissolved in oil without performing off-line and destructive tests.