In this experimental investigation the interaction of lithium with 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([OMIm]Tf2N) is shown. For this purpose thin films of lithium and [OMIm]Tf2N were successively vapor deposited on a copper substrate and analyzed by X-ray Photoelectron Spectroscopy (XPS) as well as by Ultraviolet Photoelectron Spectroscopy (UPS). When [OMIm]Tf2N is evaporated on top of a thin lithium film a chemical shift analysis of XPS spectra shows a variety of reaction products like LiF, Li2O and LixCHy which reveals the instability of the IL against lithium. Time resolved XPS spectra were discussed to distinguish cation reactions from beam damage effects. In a second step lithium is deposited on a [OMIm]Tf2N layer. The XPS spectra are in agreement with the results of the previous step, but show some differences concerning the [OMIm] cation. In a third step [OMIm]Tf2N has been deposited on a passivated lithium layer. XPS results show nearly unaffected [Tf2N](-) anions and partially decomposed [OMIm](+) cations. Interestingly the cation reactions show similarities when compared to the interaction of [C4C1Pyrr]Tf2N (1-butyl-1-methylpyrrolidinium bis[trifluoromethylsulfonyl]amide) and lithium.

The highly ordered pyrolytic graphite ( H O P G ) / 1 -o c t y l -3 -m e t h y l i m i d a z o l i u m b i s -(trifluoromethylsulfonyl)imide ([OMIm]Tf 2 N) interface is examined by ultrahigh vacuum scanning tunneling microscopy (UHV-STM), atomic force microscopy (UHV-AFM) (and as a function of potential by in situ scanning tunneling microscopy (STM)), in situ atomic force microscopy (AFM), and density functional theory (DFT) calculations. In situ STM and AFM results reveal that multiple ionic liquid (IL) layers are present at the HOPG/electrode interface at all potentials. At open-circuit potential (OCP), attractions between the cation alkyl chain and the HOPG surface result in the ion layer bound to the surface being cation rich. As the potential is varied, the relative concentrations of cations and anions in the surface layer change: as the potential is made more positive, anions are preferentially adsorbed at the surface, while at negative potentials the surface layer is cation rich. At −2 V an unusual overstructure forms. STM images and AFM friction force microscopy measurements both confirm that the roughness of this overstructure increases with time. DFT calculations reveal that [OMIm] + is attracted to the graphite surface at OCP; however, adsorption is enhanced at negative potentials due to favorable electrostatic interactions, and at −2 V the surface layer is cation rich and strongly bound. The energetically most favorable orientation within this layer is with the [OMIm] + octyl chains aligned "epitaxially" along the graphitic lattice. This induces quasi-crystallization of cations on the graphite surface and formation of the overstructure. An alternative explanation may be that, because of the bulkiness of the cation sitting along the surface, a single layer of cations is unable to quench the surface potential, so a second layer forms. The most energetically favorable way to do this might be in a quasi-crystalline/multilayered fashion. It could also be a combination of strong surface binding/orientations and the need for multilayers to quench the charge.

A comparative study of the chemical reactions of three different ionic liquids prepared by physical vapor deposition on a Li/Cu surface was performed. In this investigation, the ionic liquids 1-butyl-1-methylpyrrolidinium bis­[fluorosulfonyl]­imide ([Py1,4]­FSI), 1-butyl-1-methylpyrrolidinium bis­[trifluoromethylsulfonyl]­imide ([Py1,4]­TFSI), and 1-octyl-3-methylimidazolium bis­(trifluoromethylsulfonyl)­imide ([OMIm]­TFSI) were characterized by monochromatic X-ray photoelectron spectroscopy after adsorption on Li/Cu. All spectra prove the formation of LiF and Li2O, which verifies the partial decomposition of the anions. This is found to be much less intense for [Py1,4]­TFSI than for [Py1,4]­FSI, indicating a more rapid decomposition of the FSI anion in the presence of lithium. In addition, changes of the cation structure, as well as changes of the anion/cation ratio, were observed in the spectra. In summary, cations were most likely displaced from the Li/Cu surface and were partially decomposed, especially in case of [OMIm]­TFSI, due to the interaction with lithium. The results give an overview on the possible reaction products at the Li surface when using ionic liquids as electrolytes or additives for lithium batteries. Additionally, it gives an insight into the specific role of the cations and anions for the formation of the solid electrolyte interphase layer in battery systems.

In the current study, the potential of dry machining of the titanium alloy Ti-6Al-4V with uncoated tungsten carbide solid endmills was explored. It is demonstrated that tribo-oxidation is the dominant wear mechanism, which can be suppressed by milling in an extreme high vacuum adequate (XHV) environment. The latter was realized by using a silane-doped argon atmosphere. In the XHV environment, titanium adhesion on the tool was substantially less pronounced as compared to reference machining experiments conducted in air. This goes hand in hand with lower cutting forces in the XHV environment and corresponding changes in chip formation. The underlying mechanisms and the ramifications with respect to application of this approach to dry machining of other metals are discussed.

The supply and processing of materials for highly stressed components are usually cost-intensive. Efforts to achieve cost and resource efficiency lead to more complex structures and contours. Additive manufacturing steps for component repair and production offer significant economic advantages. Machining needs to be coordinated with additive manufacturing steps in a complementary way to produce functional surfaces suitable for the demands. Regarding inhomogeneity and anisotropy of the microstructure and properties as well as production-related stresses, a great deal of knowledge is still required for efficient use by small- and medium-size enterprises, especially for the interactions of subsequent machining of these difficult-to-machine materials. Therefore, investigations on these influences and interactions were carried out using a highly innovative cost-intensive NiCrMo alloy (IN725). These alloys are applied for claddings as well as for additive component manufacturing and repair welding using gas metal arc welding processes. For the welded specimens, the adequate solidification morphology, microstructure and property profile were investigated. The machinability in terms of finishing milling of the welded surfaces and comparative analyses for ultrasonic-assisted milling processes was examined focussing on surface integrity. It was shown that appropriate cutting parameters and superimposed oscillating of the milling tool in the direction of the tool rotation significantly reduce the mechanical loads for tool and workpiece surface. This contributes to ensure a high surface integrity, especially when cutting has to be carried out without cooling lubricants.

Sodium-ion batteries (SIBs) are emerging as potential stationary energy storage devices due to the abundance and low cost of sodium. A simple and energy efficient strategy to develop electrodes for SIBs with a high charge/discharge rate is highly desirable. Here we demonstrate that by surface modification of Ge, using electroless deposition in SbCl3/ionic liquids, the stability and performance of the anode can be improved. This is due to the formation of GexSb1-x at the surface leading to better diffusion of Na, and the formation of a stable twin organic and inorganic SEI which protects the electrode. By judicious control of the surface modification, an improvement in the capacity to between 50% and 300% has been achieved at high current densities (0.83-8.4 A g(-1)) in an ionic liquid electrolyte NaFSI-[Py1,4]FSI. The results clearly demonstrate that an electroless deposition based surface modification strategy in ionic liquids offers exciting opportunities in developing superior energy storage devices.

Group III-V semiconductor nanostructures are important materials in optoelectronic devices and are being researched in energy-related fields. A simple approach for the synthesis of these semiconductors with well-defined nanostructures is desired. Electroless deposition (galvanic displacement) is a fast and versatile technique for deposition of one material on another and depends on the redox potentials of the two materials. Herein we show that GaSb can be directly synthesized at room temperature by galvanic displacement of SbCl3 /ionic liquid on electrodeposited Ga, on Ga nanowires, and also on commercial Ga. In situ AFM revealed the galvanic displacement process of Sb on Ga and showed that the displacement process continues even after the formation of GaSb. The bandgap of the deposited GaSb was 0.9±0.1 eV compared to its usual bandgap of 0.7 eV. By changing the cation in the ionic liquid, the redox process could be varied leading to GaSb with different optical properties.

We report on a new approach to transport samples for surface analysis safely from oxidation over long distances. The transport method is based on silane-doped inert gases, which are used as a transport medium. In this paper, we show that with the help of silane, highly purified inert gas atmospheres with oxygen contents of less than 10−15 mbar can be generated. In addition, we demonstrate that compared to commercially available inert gases, silane-doped inert gas atmospheres can be efficiently used to store and transport samples safely from oxidation. For this, surface sensitive measurements on highly reactive titanium samples, which passed the different stages of samples transport, were performed. The measurements revealed that no pronounced oxidation by the silane-doped atmosphere takes place. However, adsorption of silicon oxide from the atmosphere was observed.