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Magnesium is attractive for the application as a temporary bone implant due to its inherent biodegradability, non-toxicity and suitable mechanical properties. The degradation process of magnesium in physiological environments is complex and is thought to be a diffusion-limited transport problem. We use a multi-scale imaging approach using micro computed tomography and transmission X-ray microscopy (TXM) at resolutions below 40 nm. Thus, we are able to evaluate the nanoporosity of the degradation layer and infer its impact on the degradation process of pure magnesium in two physiological solutions. Magnesium samples were degraded in simulated body fluid (SBF) or Dulbecco's modified Eagle's medium (DMEM) with 10% fetal bovine serum (FBS) for one to four weeks. TXM reveals the three-dimensional interconnected pore network within the degradation layer for both solutions. The pore network morphology and degradation layer composition are similar for all samples. By contrast, the degradation layer thickness in samples degraded in SBF was significantly higher and more inhomogeneous than in DMEM+10%FBS. Distinct features could be observed within the degradation layer of samples degraded in SBF, suggesting the formation of microgalvanic cells, which are not present in samples degraded in DMEM+10%FBS. The results suggest that the nanoporosity of the degradation layer and the resulting ion diffusion processes therein have a limited influence on the overall degradation process. This indicates that the influence of organic components on the dampening of the degradation rate by the suppression of microgalvanic degradation is much greater in the present study.

Gas-atomised spherical powders of Ti-45Al-5Nb and Ti-45Al-10Nb alloys were produced using the plasma melting induction guided gas atomisation (PIGA) technique. The phase composition was determined by X-ray diffraction at the synchrotron beamline HEMS at PETRA III (DESY), as well as by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), two dimensional and focused ion beam (FIB) based three dimensional electron back scatter diffraction (EBSD) measurements. Due to the high cooling rates the alloy composition of both alloys consists of hexagonal-close-packed α- and body-centred-cubic β-phase. The α-phase is dominant in the larger powder size fractions. Considerable amounts of the β phase were only found in the powder particle size fractions smaller than 32 μm for the Ti-45Al-5Nballoy and smaller than 45 μm for the Ti-45Al-10Nb. A pronounced dendritic cauliflower-like structure was observed in bigger powder particles of the Ti-45Al-10Nb alloy. This gives proof that diffusion took place during the initial β-grain formation, even though there is no orientation relation between the final grain and the dendrite structure in the powder particles. The presence of dendritic structures showed that the cooling rate during powder atomization was still too low to reach the critical growth rate for a planar solidification. The absence of preferred misorientation angles between α-grains indicates that α-grains are not formed out of already solidified β-grains by a solid state phase transformation.

The reactive hydride composite of 2LiBH4–MgH2has been melt infiltrated in a resorcinol–furfural (RFF) carbon aerogel scaffold. Dried aerogel of RFF, further pyrolyzed to obtain a carbon aerogel scaffold, is prepared by CO2supercritical drying, where time consumption is significantly lower than the normal procedures of solvent exchange and drying under ambient conditions. On the basis of scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDS) mapping, the complex hydrides are homogeneously dispersed in the nanometer scale both inside the nanopores and over the surface of the RFF carbon aerogel. Synchrotron radiation powder X-ray diffraction (SR–PXD) and Raman results reveal the reaction mechanisms during melt infiltration, de- and rehydrogenation of this system, as well as the differences from the previous studies of the nanoconfined 2LiBH4–MgH2in a resorcinol–formaldehyde (RF) carbon aerogel. Thermogravimetric and hydrogen titration measurements reveal a significant improvement in dehydrogenation kinetics of 2LiBH4–MgH2–RFF as compared with the bulk 2LiBH4–MgH2system. For instance, an approximate single-step dehydrogenation together with almost 100% of the total hydrogen storage capacity is accomplished within 6 h during the first dehydrogenation, while the bulk material performs clearly two-step reaction and requires ∼30 h (at T= 45 °C and p(H2) = 3–4 bar). Moreover, the gravimetric hydrogen storage capacity in the range of 4.2–4.8 wt % (∼10–11.2 wt % H2with respect to the hydride content) is maintained over four dehydrogenation and rehydrogenation cycles.

Nanoconfined 2LiBH4–MgH2is prepared by direct melt infiltration of bulk 2LiBH4–MgH2into an inert nanoporous resorcinol–formaldehyde carbon aerogel scaffold material. Scanning electron microscopy (SEM) micrographs and energy dispersive X-ray spectroscopy (EDS) mapping reveal homogeneous dispersion of Mg (from MgH2) and B (from LiBH4) inside the carbon aerogel scaffold. Moreover, nanoconfinement of LiBH4in the carbon aerogel scaffold is confirmed by differential scanning calorimetry (DSC). The hydrogen desorption kinetics of the nanoconfined 2LiBH4–MgH2is significantly improved as compared to bulk 2LiBH4–MgH2. For instance, the nanoconfined 2LiBH4–MgH2releases 90% of the total hydrogen storage capacity within 90 min, whereas the bulk material releases only 34% (at T= 425 °C and p(H2) = 3.4 bar). A reversible gravimetric hydrogen storage capacity of 10.8 wt % H2, calculated with respect to the metal hydride content, is preserved over four hydrogen release and uptake cycles.