## 2 Materials and Methods
### Experimental Procedure  
Before surface preparation, the fabricated aluminum specimens were cleaned with acetone and a lint-free cloth. To achieve a comparable initial surface condition for all atmospheres, the surfaces were sanded with P280 grit sandpaper. The result is an aluminum surface with an average arithmetic roughness of 1.1 \(\pm\) 0.1 \(\upmu\)m, which was measured in all atmospheres using the roughness measuring device MarSurf PS 10 from Mahr GmbH. The values of the adherends in individual atmospheres with and without oxide layer did not differ within the standard deviation and were therefore given as one mean value. The surfaces were then cleaned again with a lint-free cloth to remove any grinding residues. To prevent solvent contamination of the atmosphere, cleaning with acetone after grinding was not carried out. The sample heads were then screwed onto the sample holders and one side was placed in the bonding mold. A drop of the respective adhesive was placed on the bonding surface of the opposite side. This side was also placed in the bonding mould, the magnetic holders were placed on top, and then the locking pin was closed. To ensure that curing was complete, a curing time of seven days was observed in accordance with the manufacturer's data sheets. The specimens were then hooked into the tensile testing machine, and a tensile test to failure was performed. Eight pairs of specimens were tested for each of the different atmospheres. For the normal atmosphere, the specimens were ground, bonded and tested for tensile strength. For the argon and argon/silane atmospheres, two sets of tests were performed in each case. On the one hand, it was grounded outside the box to allow the formation of an oxide layer. On the other hand, it was grounded inside the glove box at the respective atmosphere. For the argon atmosphere, it is assumed that an oxide layer is formed because sufficient oxygen is present. For the argon/silane atmosphere, it is assumed that the oxide layer is removed  
Figure 6: (**a**) Specim bodies bonded together and hooked into the chuck grips. (**b**) Universal tensile testing machine in shortened version inside the glovebox. In the case of the epoxy resin-based adhesive Scotch-Weld DP 410, it is noticeable that the results for the standard atmosphere are the lowest at around 31 MPa. The values for bonding in an argon atmosphere, as well as for the argon/silane atmosphere without an oxide layer, are the highest, all at about the same level of just under 48 MPa. Only the results for the tests in an argon/silane atmosphere with intermediate oxide layers are clearly below this value with about 35 MPa, but still slightly higher than the values for the normal atmosphere. For the DP 410 adhesive, the manufacturer only gives the shear strength, which is 25 MPa for roughened aluminum surfaces. However, since tensile strengths are generally higher than shear strengths, the values cannot be compared with those of the manufacturer. Since, to the authors' knowledge, no studies of bonding without an oxide layer have been performed by other researchers, unfortunately no comparison with previous results can be discussed here. The polyurethane-based adhesive Scotch-Weld DP 610 generally achieves lower tensile strengths as shown in Figure 8. The average tensile strength values for this adhesive are between 14 and 22 MPa. The values for the normal atmosphere are also lower for this adhesive than for the other atmospheres. The results in argon atmosphere oxidized and deoxidized, as well as the results for argon/silane atmosphere oxidized, are roughly on a level with values between 16 and 18 MPa, taking into account the standard deviation. Only the values for the deoxidized samples in the argon/silane atmosphere reach higher values, around 22 MPa. Thus, the tensile strengths for the deoxidized specimens are more than 50% higher than those in normal atmosphere.