Synthesis of TiB2-Ni3B nanocomposite coating by DC magnetron sputtering for corrosion-erosion protection

Significant contribution on corrosion-erosion resistance of Ni3B-TiB2 nanocomposite coating of 1µm of thickness, deposited by DC magnetron Sputtering on stainless steel 304 substrates was studied. Nickel phase (γ Ni) plus Ni3B-TiB2 phases were synthesized previously by Mechanical Alloying (MA). Solid cathode (76.2 mm of diameter and 3 mm of thickness) used to grow thin films was manufactured with the alloyed powders, applying a uniaxial load of 70 MPa at room temperature and sintered at 900° C for two hours. Microstructure and mechanical properties of the coatings were characterized by X-Ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), nanoindentation, and wear test with a ball-on-disc tribometer. Compact coating of Ni3B-TiB2 with a microstructure of prismatic crystals after annealing treatment, showing a uniform coating with good adherence and low friction coefficient of 0.5, correlated with a low roughness of Ra ≈ 0.0439±0.0069 µm. The average hardness of 537.4 HV (5265.0 MPa) and wear coefficient at room temperature of 2.552E-10 m2N-1 correspond with medium-hard phases with an elastic-plastic behavior suitable for fatigue applications. Geothermal fluid modified was synthesized in the lab with NaCl/Na2SO4 to evaluate the corrosion resistance of the films in a standard three electrodes cell, characterizing a corrosion rate of 0.0008 and 0.001 mm*year-1 at 25 and 80°C respectively during 86.4 ks (24 h) of exposition; showing a resistive coating without corrosion products and with good response to the geothermal environment.

Effect of Deposit on the Evaporation Rate of Adhered Salt in Uranium Dendrite

Electrorefining is a key step in pyroprocessing. The solid cathode processing is necessary to separate the salt from the cathode of the electrorefiner since the uranium deposit in a solid cathode contains electrolyte salt. Moreover, it is very important to increase the throughput of the salt separation system due to the high uranium content of the spent nuclear fuel and high salt fraction of uranium dendrites. Therefore, in this study, the effect of deposit on the evaporation of the adhered salt in a uranium deposit was investigated by using the samples of salt in the uranium deposit and salt in the deposit of the surrogate material for the effective separation of the salt. It was found that the salt evaporation rate is dependent on the deposit type and bulk density in the crucible. Additionally, the evaporation rate was found to be lower when the deposit structure is complex; the rate also decreases as the bulk density of the deposit is increased owing to the retardation of the salt vapour transport process. It was concluded that the mass transfer of the salt vapour is an important parameter for the achievement of a high throughput performance in the salt distillation process.

Effect of Milling Process and Calcination Temperature on the Properties of BSCF-SDC Composite Cathode

The ionic conductivity, super conductivity, ferroelectricity, and magnetic resistance of barium strontium cobalt ferrite (BSCF) make it a good solid cathode material. This study aims to investigate the influence of milling process and calcination temperature on the behaviour of nanocomposite cathode BSCF–samarium-doped ceria (SDC). The BSCF–SDC composite powders were mixed using two milling processes, namely, wet milling and dry milling. The composite cathode powders were mixed through wet milling by high-energy ball milling at 550 rpm for 2 hours. For dry milling, the powders were milled at 150 rpm for 30 minutes. The powders then underwent calcination at 900 °C, 950 °C, 1050 °C, and 1150 °C for 2 hours. The composite cathodes were examined on the basis of phase and microstructure through field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD), respectively. In conclusion, the selection of suitable milling process and calcination temperature is important in eliminating secondary phases in BSCF–SDC composite cathodes and in enhancing their properties.