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[en] This report describes the progress made in IFREC/DEMO Research and Development Program during the year 2010 at SCK/CEN. This task is part of demonstrating the possibility to irradiate small specimens in the HFTM modules that will be used in DEMO. Different small specimens of three candidate materials of DEMO fusion reactor will be irradiated with the objective of validating the specimen geometry and size to reliably characterize the mechanical properties of unirradiated and in future of irradiated materials.
[en] An attempt is made to outline the new challenges faced by the community of Moessbauer spectroscopists with a special focus on India. Some suggestions are made to overcome these challenges.
[en] The use of cellulosic fibers as reinforcing materials in polymer composites has gained popularity due to an increasing trend for developing sustainable materials. In the present experimental study, flax and glass fiber reinforced partially eco-friendly hybrid composites are fabricated with two different fiber orientations of 0° and 90°. The mechanical properties of these composites such as tensile, flexural and impact strengths have been evaluated. From the experiments, it has been observed that the composites with the 0° fiber orientation can hold the maximum tensile strength of 82.71 MPa, flexural strength of 143.99 MPa, and impact strength of 4 kJ/m2. Whereas the composites with 90° fiber orientation can withstand the maximum tensile strength of 75.64 MPa, flexural strength of 134.86 MPa, and impact strength of 3.99 kJ/m2. Morphological analysis is carried out to analyze fiber matrix interfaces and the structure of the fractured surfaces by using scanning electron microscopy (SEM). The finite element analysis (FEA) has been carried out to predict the resulting important mechanical properties by using ANSYS 12.0. From the results it is found that the experimental results are very close to the results predicted from FEA model values. It is suggested that these hybrid composites can be used as alternate materials for pure synthetic fiber reinforced polymer composite materials.
[en] This research examines the deposition of Cr3C2-NiCr/cenosphere and Cr3C2-NiCr coatings on MDN 321 steel through the process of plasma spray. In this process, the solid particle erosion test is established at 200, 400, 600 °C with 30° and 90° impact angles. Alumina erodent is adopted to investigate the erosive behavior of the coating at higher temperatures. The properties of the Cr3C2-NiCr/cenosphere coating are established based on the microhardness, the adhesive strength, the fracture toughness, and the ductility. To quantify volume loss as a result of erosion, an optical profilometer is used. At higher temperature, decrease in the erosion volume loss of Cr3C2-NiCr/cenosphere and Cr3C2-NiCr coatings is observed. The erosion-resistive property of Cr3C2-NiCr/cenosphere coating is higher than that of MDN 321 steel by 76%. This property is influenced by high-temperature stability of mullite, alumina, and protective oxide layer that is formed at elevated temperatures. The morphology of eroded coating discloses a brittle mode of material removal.
[en] Oxide dispersion strengthened (ODS) steels with high Cr-content are extensively investigated in Europe, Japan and United States by the nuclear materials community for application to both advanced fission reactors and fusion systems. In comparison to standard high Cr-steels, the expected operation temperature range can be extended to 650 °C or more because of their improved creep resistance. However, their crack resistance behavior in the high temperature range was less investigated. The aim of the present paper is to provide some insight on their fracture behavior at high temperature and different crack configurations, in particular shallow crack. Crack resistance measurements were performed on a 12%Cr-ODS steel using compact tension specimens at 650 °C considering both shallow and deep crack configurations. Finite element calculations were performed on a typical fuel cladding tube geometry to assess the performances in terms of crack resistance. It is found that the temperature gradient across the wall should be maintained low enough to avoid cracking. After irradiation in corrosive environment, the boundary conditions might be further affected limiting therefore the lifetime of ODS cladding
[en] In this paper, investigation into solid particle erosion behavior of atmospheric plasma-sprayed composite coating of CoCrAlY reinforced with Al2O3 and CeO2 oxides on Superni 76 at elevated temperature of 600 °C is presented. Alumina particles are used as erodent at two impact angles of 30° and 90°. The microstructure, porosity, hardness, toughness and adhesion properties of the as-sprayed coatings are studied. The effects of temperature and phase transformation in the coatings during erosion process are analyzed using XRD and EDS techniques. Optical profilometer is used for accurate elucidation of erosion volume loss. CoCrAlY/CeO2 coating showed better erosion resistance with a volume loss of about 50% of what was observed in case of CoCrAlY/Al2O3/YSZ coating. Lower erosion loss is observed at 90° as compared to 30° impact angle. The erosion mechanism evaluated using SEM micrograph revealed that the coatings experienced ductile fracture exhibiting severe deformation with unusual oxide cracks. Reinforced metal oxides provide shielding effect for erodent impact, enabling better erosion resistance. The oxidation of the coating due to high-temperature exposure reforms erosion process into oxidation-modified erosion process.
[en] The influence of composite coating in improving wear and frictional behavior from room temperature to 600 °C was investigated. Partially oxidized Al powder was prepared with a flame spray process by spraying pure Al powder into distilled water. The composite powder is the mixture of 30 weight percent of partially oxidized Al and 70 weight percent of NiCr alloy powder. The composite powder was subsequently coated on MDN321 steel by air plasma spray process. The composite coatings are characterized with respect to adhesion strength, porosity, micro-hardness, and density. Wear and frictional behavior of coatings are evaluated under disc speed of 1 and 2 m s−1, loads of 10, 20 and 30 N and 3000 m sliding distance. The test results indicated that at room temperature, frictional heat generated due to applied load produce three-body abrasion at the interface caused to increase the wear and friction in the coating. The oxide film formed at high temperature due to plastic deformation avoids surface degradation at the interface and reduce the wear and friction. The worn surfaces at 600 °C consist phases of α-Al2O3, NiO, and Cr3O. These phases are contributing to improving the wear resistance of the coating more than 4-times compared to uncoated steels under varying load and sliding velocities. The coefficient of friction reduced with increase in temperature due to generated oxides act as lubricants at the interface. (paper)
[en] Detector grade Cd0.9Zn0.1Te (CZT) single crystals were grown from zone refined Cd, Zn, and Te (∼7 N) precursor materials, using a tellurium solvent method. Detectors with virtual Frisch grid configuration were fabricated using these crystals. I-V measurements revealed low leakage currents at room-temperature, ∼11 nA for one such detector D1 and ∼8 nA for another detector D2 at 1100 V. The spectroscopic performances of the two CZT virtual Frisch grid detectors have been evaluated and compared for high energy gamma ray detection. Detector D1 showed a well-resolved pulse-height spectrum with an energy resolution of ∼1.6% for the 662 keV gamma rays. Detector D2 also showed a distinct 662 keV peak but with a broader pulse-height distribution. A digital biparametric correlation study of the depth of interaction and energy deposited by the 662 keV gamma rays was carried out. A different kind of correlation pattern from that observed normally for hole trapping was noticed in the case of detector D2. Correlation of results from thermally stimulated current measurement studies suggested that the anomalous biparametric correlation pattern was due to the trapping of holes but modified by the virtual Frisch grid effect. The results also suggested that the effect of electron trapping could not be ruled out either. Finally, a digital correction scheme was applied to recover the 137Cs spectrum from the effect of charge loss.
[en] 0.8BaTiO_3 – 0.2(Bi_0_._5_(_1_-_x_)Nd_0_._5_xK_0_._5)TiO_3 (0.01 ≤ x ≤ 0.06) lead free ceramic materials have been prepared by solid state reaction method and followed by high energy ball milling process. X-ray diffraction studies confirm the tetragonal structure of the materials at room temperature. Lattice parameters and density are decreasing with increase of Nd substitution. Microstructure studies were done by using Scanning electron microscope and it found that grain size is decreasing with increase of Nd substitution. Temperature and frequency dependent dielectric studies reveal relaxor behaviour of the materials. Dielectric constant, dielectric loss and Curie temperature are decreasing with Nd substitution. Maximum Curie temperature of 195°C was observed at 1 MHz for x=0.01 Nd substituted sample. Degree of diffuseness was calculated from the modified Curie-Weiss law and it is increasing with Nd substitution. AC conductivity is increasing with increase of Nd substitution and observed maximum activation energy of 0.52 eV for x=0.02 Nd substituted sample.
[en] The fretting wear and adhesive wear resistance of Ti-based thin solid films deposited on MDN121 steel substrate are evaluated. Plasma-assisted cathodic arc evaporation technique is used to develop the TiC–C monolayer coating and Ti/TiN/TiCN/TiN/TiCN multilayer coatings used in the study. FESEM-EDS, nanoindentation, Raman spectroscopy, optical profiler, and confocal microscope are used to characterise the coatings and wear tracks. Diamond-like carbon is observed in the microstructure of both the coatings. During the fretting analysis, the coefficient of friction (COF) is reduced by 68.49% in the case of the TiC–C monolayer coating and 42.46% in the Ti multilayer coatings as compared to the substrate. The volumetric wear loss of the TiC–C monolayer coating is lower than the multilayer coating. The wear surface morphology reveals the abrasive form of the fretting wear mechanism in both the monolayer and multilayer coatings whereas the galling failure in the substrate. During adhesive wear, the COF is reduced by 71.73% in the monolayer coating and 59.33% in the multilayer coatings compared to the substrate. The monolayer coating exhibits low friction and low wear rate as compared to the multilayer coating. (paper)