Search

Zircaloy-4 has an important role in the construction of generation III nuclear reactors. An important application is the fuel element sheath, which must have excellent corrosion resistance in the working environment, adequate mechanical characteristics and very good heat transfer properties from the combustible element to the coolant. The corrosion processes at high temperatures, the accidents that lead to significant increases in temperature and the structural transformations associated with them affect the heat transfer process. The paper presents research on the influence of high temperatures on the microstructure and thermal diffusivity of the zy-4 alloy. The samples were treated in air, at temperatures between 850 and 1050 °C for 60 min. The corrosion layers were characterized microstructurally and chemically. Furthermore, the transformations produced in the base material under the corrosion layer were analyzed. The values of thermal diffusivity were determined and correlated with the structural transformations. Considering the state of research on the materials appropriate to be used for new generation reactors, the current importance of third-generation reactors for energy systems and the fact that they will operate in the coming years, we consider that the study offers useful outcomes in the field of nuclear energy.

Combined analysis methods such as optical microscopy (OM), cathodoluminescence (CL) microscopy, X-ray diffraction (XRD), and scanning electron microscopy–energy dispersive X-ray spectrometry (SEM–EDX) have made it possible to obtain the first physico-chemical data of Dacian potsherds, exhumed at the archeological site of Ocnița-Buridava, Romania, the samples were provided by the “Aurelian Sacerdoțeanu” County Museum Vâlcea, dating from the 2nd century BC to the 1st century AD. The mineralogical and petrographic analyses revealed two types of ceramic pastes, taking into account the granulometry of the inclusions and highlighting the choice of the potter for fabricating the ceramic either by wheel or by hand. All samples showed an abundance in quartz, mica (muscovite and biotite), and feldspars. These observations were confirmed by cathodoluminescence imagery, revealing heterogeneous pastes with varied granulometric distributions. The XRD patterns indicated the presence of the mineral phases, indicating a firing temperature below 900 °C. The wheel-made ceramics have a fine, compact matrix with very fine inclusions (&lt, 40 µm). On the other hand, the hand-made ceramics present a coarse matrix, with inclusions whose granulometry reaches approximately 2 mm. The difference between these two types of ceramics is also confirmed by the mineralogical and chemical analysis. The wheel-made potsherds are more abundant in MgO, Al2O3, and CaO contents.

Materials engineering involves knowledge of the fundamental physics, chemistry and engineering of materials in order to elaborate, develop, and use materials with superior and new properties. The research, development and applications of materials are the major reasons behind the availability, cost reduction, innovations and improvements in all the fields of industry. Master's programs are designed to give you a solid (strong) education in the materials engineering field. Students entering a Master program have already earned a bachelor's degree and have solid acquirement of engineering. The program entails coursework, examinations and an internship or other applied experience. A master report is required to obtain the masters degree based on the researches during the stage. During a Master programme the students learn to approach complex issues from the perspective of different disciplines such as: characterisation of materials, thermodynamics, structurals transformations, technology of materials, properties of surfaces or initiation on research methods. By understanding the properties of materials, materials engineers create new materials with desired properties. Students entering a Ph.D. program have already earned a a masters degree in the field of „Materials engineering". Because of the nature of specialization the Ph.D. program tends to be smaller than master program. The international orientation of the practice stage approaches to of the Erasmus mobilites. A Ph.D. typically demonstrates a person's competence in research. Ph.D. students begin by taking courses and exams, go on to taking advanced seminars and preparing dissertation research. To complete their knowledges, they are continuing by researching, writing and completeing a dissertation thesis. The doctoral-level thesis, is the culmination of a Ph.D. candidate's research into a topic and is the major requirement of earning the doctorate. A doctoral degree is obviously a more advanced degree. However, it is long. Depending on the program, a PhD could take 4-8 years to complete. A PhD programs entails 3 years of coursework and a dissertation. During this these years the independent researchs projects are designed to cover new knowledge in your field and to be of publishable quality. Doctoral study offers the unique opportunity for an individual to develope intensive and prolonged research on a particular topic, which often leads to publication. The present paper presents the association of Romanian and French university teachers to educate students to prepare a Master diploma and to continue with cotutelle doctoral studies in the field of materials engineering.

For the last 30 years, AA2024 aluminum alloy was very used as structural material in the aerospace industry due to its low density and good mechanical strength. The phenomenon of precipitation hardening in aluminum alloys takes place at relatively low temperature and induces the precipitation of intermetallic particles composed of the main alloying elements i.e., copper and magnesium. The fundamental stage of the age-hardening process consists in the acceleration of the decomposition phenomenon of the supersaturated solid solution, resulting in the coarse intermetallic particle precipitation; stage where the mechanical properties reaches the maximum values, but at the cost of a low corrosion resistance. In this paper, the AA2024 alloy microstructure was studied during the over-ageing process. The over-ageing treatment (T7) is supposed to stabilize the microstructure and the mechanical properties to improve the corrosion resistance. The over-ageing treatment consists in a solution treatment at 495±5°C for 1 hour, quenched into cold water and artificial aged. Three different artificial ageing temperatures were studied: 150°C, 175°C and 190°C. The mechanical properties modifications were followed by Vickers macrohardness measurements. The treatment duration for each temperature (36 days for 150°C, 50 hrs for 175°C and 24 hrs for 190°C) was determined by a given macrohardness reduction. To characterize the over-aged AA2024 alloy microstructure, a statistical analysis of the surface fraction and surface density of intermetallic particles was made. The intermetallic particle dimension distribution, depending on the over-ageing temperature, was also observed. To do so, scanning electron microscope observations were carried out and image analyses were performed from backscattered electron images.

The 2xxx serie aluminum alloys are characterized by good mechanical performances and low density, however they are susceptible to different forms of localized corrosion: pitting corrosion, intergranular corrosion and stress corrosion cracking. The 2024-T351 aluminum alloy is used in the aircraft industry for numerous applications such as fuselage and door skin. Corrosion damage of the material is also very detrimental for the structural integrity of the aircraft. The presence of coarse intermetallic particles, with a heterogeneous size distribution was found to be responsible for the 2024 susceptibility to localized corrosion. These particles are generally the cause of initiation sites. Presence of micro-defects in the oxide film upon coarse intermetallic particles and the galvanic coupling with the matrix contribute to the development of pitting corrosion. The over-ageing treatment (T7) is supposed to stabilize the microstructure and the mechanical properties to improve the corrosion resistance. The 2024 alloy microstructure after the T7 heat treatment remains very complex. The 2024 alloy corrosion behavior was studied in the over-ageing state for three different temperatures (150, 175 and 190 °C). During the corrosion tests in chloride-containing environment, the behavior of coarse intermetallic particles was found to be different. Thus, the 2024 samples suffer a gradual attack upon S-Al2CuMg particles and finally Al (Cu,Mn,Fe,Si) particles. The corrosion damage was studied by Atomic Force Microscopy (AFM) and Kelvin probe Force Microscopy (KFM). This technique allows simultaneous topographical and electric potential mapping to be obtained. This latest potential was shown to be correlated to the corrosion potential of the 2024 alloy. This study focuses on the variation of the KFM potential of the coarse intermetallic particles and the matrix for the over-ageing conditions (T7). Observations using optical microscope and AFM were also performed to obtain the corrosion rate for each condition. The corrosion rate was correlated to the chemical composition variation of the particles obtained by scanning electron microscope observations and EDS analyses.

Transmission electron microscopy, XPS analysis, electrical conductivity and diffusion measurements were used to characterize the transport properties and grain boundary segregation phenomena in 9 mol% yttria-stabilized zirconia (YSZ). The highest grain boundary electrical conductivity (σgb) and oxygen diffusion coefficient (DO) values are shown by samples with a cleaner microstructure, sintered at 1600 °C and rapidly cooled at the end of sintering. XPS measurements show that an yttrium and silicon kinetic demixing process takes place during cooling. The amount of silicon rejected in the grain boundaries decreases when the cooling rate at the end of sintering increases, in agreement with the highest grain boundary conductivity values of the quenched samples. A formal treatment has allowed us to show that these results can be explained by the two competing effects occurring during cooling: the cation redistribution kinetics and the cooling rate.

The geometry of Al 2 O 3 –TiO 2 (13 wt.%) plasma-sprayed deposits produced on flat coupons with various spray gun kinematic parameters was analyzed by several methods: a precise co-ordinates measuring machine (CMM), a laser profilometer, a stylus roughness measuring tester and optical microscopy. A comparative study of these methods was performed. To quantify the deposit geometry a set of parameters was implemented. The deposit morphology was discussed with respect of the deposition timeframe, spray angle and number of passes. At low thickness, the deposit is discontinuous due to the discrete nature of plasma spray deposition, while the profile of thicker deposits is continuous and exhibits a normal distribution. A homothetic growth of deposit with the number of passes was observed. The geometric information was combined to define the geometry of a deposit model to be used for optimization of robotic trajectories in Atmospheric Plasma Spraying (APS).