Apollo xp

Scanning Electron Microscopy (SEM) measurements were conducted using an Auriga microscope (Zeiss, Oberkochen, Germany) equipped with an Energy Dispersive X-ray Spectroscopy (EDX) device (Apollo XP from EDAX, Ametek GmbH, Wiesbaden, Germany). The SEM images were obtained at an accelerating voltage of 2 kV with the SE2—detector. Cross sections of the SC and negative control samples (SNC) were prepared by ion beam milling at 30 keV using a gallium focused ion beam (FIB) attached to the Auriga. To prevent damage to the cells and the corrosion layer as well as to obtain a precise cut along the degradation layer, a layer of platinum was deposited on the surface by the Gas-Injection-System (GIS). Five EDX—line scans were performed directly after FIB milling at 15 keV to define the vertical element distribution of the degradation layer on the cross-sections. The EDX scans were conducted in 8 regions of interest in the respective EDX spectrum, i.e., carbon (C), nitrogen (N), oxygen (O), sodium (Na), Mg, phosphorus (P), sulphur (S) and calcium (Ca), complemented by the alloying elements of the respective sample, i.e., Ag and Gd. Each degradation layer cross section was analysed using this method. To obtain a high counting rate for the EDX analysis, the SEM aperture (120 μm diameter) was used in high-current mode.

The degraded surfaces and their chemical composition were investigated. Samples were immersed in α-MEM + 15% FBS + 1% p/s for the longest immersion time (72 h) to analyse possible differences in elements composition between the different alloys. Samples were then dried for 24 h in vacuum and analysed by energy dispersive X-ray spectroscopy (EDX; Apollo XP, EDAX, Ametek GmbH, Wiesbaden, Germany) equipped to a scanning electron microscope (SEM; Auriga, Zeiss, Oberkochen, Germany). Surface measurements were done by accelerating voltage of 10 keV with the secondary electron detector (SE2) aiming to analyse the corroded surface and avoid the high contribution of magnesium in the bulk. Points of interests on the surface were analysed as well. The measurements were done semi-quantitatively without standard sample. EDX quantification was realized on all samples with eight common elements of interest; Mg, O, P, C have been considered despite of the alloying elements in each alloy. To obtain a high counting rate by EDX measurements the SEM aperture of 120μm diameter had been used in High Current mode.