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Purpose The study aimed to identify the environmental hotspots of lab-scale preparation of high purity porous Al2O3 pellets with suitable feature to work properly as metal layer-based deposition substrates for hydrogen separation membranes. The work intention was providing hints that may help the designing of upscaled systems, fundamental for the development of a possible future industrial production of hydrogen separation metal layer-based membranes technology. Methods The goal of this study was achieved assessing and analyzing environmental impacts of Al2O3 pellet production at lab scale. Primary data were collected in Padua laboratories of National Research Council of Italy. Secondary data were retrieved from Ecoinvent 3.7 database. Life cycle assessment (LCA) was performed using Environmental Footprint 3.0 method employing SimaPro 9.3 as software. Moreover, the CML LCIA method v. 4.7 was used to verify the robustness analysis of characterized results. Results Life cycle impact assessment highlighted as the main driver of environmental impacts was mainly associated to the pellet consolidation process and their morphological characterization stage. In particular, the impact of the first energy consuming process resulted strictly related to the peculiar energy mix used (linked to the laboratory geographical location). Conversely, morphological characterization stage was found to affect mainly the mineral resource depletion category due to the Au coating used for performing scanning electron microscope (SEM) analyses. Conclusions The study identified the environmental hotspots related to lab-scale preparation of porous alumina pellets as substrate for hydrogen separation metal layer-based membranes. The optimization strategies evaluated in this work were addressed to improve the environmental profile of experimental activities considering several scenarios, in view of a possible industrial scale-up.

Ultrafast high-temperature sintering (UHS) is a recently proposed technique able to synthesize and sinter dense materials within seconds. Although UHS has already proved its effectivity with a large set of materials, spanning from refractory ceramics to complex metal alloys, any application to thermoelectric materials is today still lacking. Mg2Si is a well-established thermoelectric material. It is based on wide available non-critical raw materials, it is non-toxic, lightweight and it expresses its best thermoelectric performances in the intermediate temperature range (up to about 600 °C). Mg2Si is typically produced with powder processing by Spark Plasma Sintering (SPS), partially limiting its widespread diffusion also due to the costly production technique. Here we present a simple route to sinter Mg2Si pressed powders by UHS. The process allowed to obtain dense samples (with relative densities >95%) with 20 s heating up to about 1080 °C followed by a rapid free cooling, a total thermal history below 1 min, and with energy demand at the Wh scale. The high process rate proved its efficacy in preventing grain growth and in avoiding any significant Mg evaporation. A full thermoelectric functional characterization is presented for Mg2Si and Bi-doped Mg2Si, together with a comparison with SPS-produced properties.

Lithium wall conditioning has improved the performance of many magnetic fusion devices. Li conditioning in the RFX-mod device was performed by: (1) a single Li pellet injector and (2) a multi-Li pellet injector during He plasma discharges; (3) a Li evaporator after He glow discharge cleaning and He plasma discharge exposure. This report compares the spatial and depth distributions of Li deposited on polycrystalline graphite witness samples at different locations in RFX-mod and the elemental and chemical compositions of the resulting surfaces. The sample surfaces were analyzed ex situ using secondary ion mass spectrometry (SIMS) and high-resolution X-ray photoelectron spectroscopy (HR-XPS). The results showed that Li pellet injection provided a relatively uniform toroidal coverage while Li evaporation produced highly localized Li deposition. A Li 1s HR-XPS peak at 56.5 eV binding energy (BE) characteristic of lithium-intercalated graphite was only observed with the sample exposed to Li evaporation. All of the samples exhibited a HR-XPS C 1s peak at 285.1–285.2 eV BE that is largely attributed to hydrogenated graphite. This finding suggests that hydrogenation of fresh graphite occurs during He plasma discharge exposures. Our results have implications for density control and the selection of Li conditioning techniques in magnetic fusion devices.