Smooth crack-free targets for nuclear applications produced by molecular plating

Abstract

The production process of smooth and crack-free targets by means of constant current electrolysis in organic media, commonly known as molecular plating, was optimized. Using a Nd salt, i.e., [Nd(NO3) 3·6H2O], as model electrolyte several constant current density electrolysis experiments were carried out to investigate the effects of different parameters, namely the plating solvent (isopropanol and isobutanol mixed together, pyridine, and N,N-dimethylformamide), the electrolyte concentration (0.11, 0.22, 0.44 mM), the applied current density (0.17, 0.3, 0.7, and 1.3 mA/cm2), and the surface roughness of the deposition substrates (12 and 24 nm). Different environments (air and Ar) were used to dry the samples and the effects on the produced layers were investigated. The obtained deposits were characterized using γ-ray spectroscopy for determining Nd deposition yields, X-ray photoelectron spectroscopy for chemical analysis of the produced surfaces, radiographic imaging for surface homogeneity inspection, atomic force microscopy for surface roughness evaluation, and scanning electron microscopy for surface morphology investigation. The results allowed identifying the optimum parameters for the production of smooth and crack-free targets by means of molecular plating. The smoothest layers, which had an average RMS roughness of ca. 20 nm and showed no cracks, were obtained using 0.22 mM [Nd(NO3)3·6H2O] plated from N,N-dimethylformamide at current densities in the range of 0.3-0.7 mA/cm2 on the smoothest deposition substrate available

Quantitative molecular plating of large-area 242Pu targets with improved layer properties

“…The SEM images of Section 3 show that the volatility of this solvent is indeed too high to produce crack-free layers. Despite this, the application of other parameters found previously effective for the quantitative preparation of quality lanthanide layers (Vascon et al, 2012(Vascon et al, , 2013a(Vascon et al, , 2014 proved useful also for the MP of Pu. Variables like current density, electrolyte concentration, and surface roughness of the deposition substrate were indeed carefully selected in order to reproduce the results obtained with lanthanide elements.…”

“…In one of our recent publications (Vascon et al, 2013a) we have explained the influence of the solvent on the properties of the MP produced layers. Solvent electrolysis occurring during the plating process causes the deposited layers to be composed of both physisorbed and chemisorbed solvent molecules (Vascon et al, 2012(Vascon et al, , 2014, whose volatility affects the stress experienced by the deposit during drying (Vascon et al, 2013a).…”

“…Solvent electrolysis occurring during the plating process causes the deposited layers to be composed of both physisorbed and chemisorbed solvent molecules (Vascon et al, 2012(Vascon et al, , 2014, whose volatility affects the stress experienced by the deposit during drying (Vascon et al, 2013a). In general, the larger the volatility of the solvent (i.e., the lower the boiling point, Bp), the larger the stress and thus the probability of cracking and delamination of the layer (Malzbender and De With, 2000).…”

“…In general, the larger the volatility of the solvent (i.e., the lower the boiling point, Bp), the larger the stress and thus the probability of cracking and delamination of the layer (Malzbender and De With, 2000). In the case of isopropanol, the boiling point is rather low, i.e., 82.2 1C (Izutsu, 2002) and for this reason during experiments with lanthanides the use of N,N-dimethylformamide-DMF (Bp¼153.0 1C) was suggested (Vascon et al, 2013a). MPs with this solvent showed that layers without cracks can be produced.…”

“…Extensive investigations of the molecular plating process have been carried out to elucidate the basic features of this electrochemical technique (Vascon et al, 2012(Vascon et al, , 2014. Plating variables critically influencing layer properties like homogeneity, surface roughness, and morphology have been identified and this has allowed for the production of homogeneous, smooth, and crack-free layers (Vascon et al, 2013a). The improved properties of these layers have also turned out to positively affect their performance in nuclear spectroscopy experiments (Vascon et al, 2013b).…”