Chromium (Cr), manganese (Mn) and carbon (C) are well known alloying elements used in technologically important alloy steels and advanced high strength steels. It is known that binary Crc(x) and MnCx carbides can be formed in steels, but in this study we reveal for the first time that Cr and Mn were found combined in novel ternary cementite type (Cr, Mn)C carbides. Electron diffraction experiments showed that Cr, Mn and C formed two distinct carbide phases possessing orthorhombic and monoclinic crystal structures. Density functional theory calculations were performed on these phases and excellent agreement was found between calculations and experiments on the lattice parameters and relative atomic positions. The calculations showed that the combination of Mn and Cr resulted in a very high thermodynamic stability of the (Cr, Mn)C carbides, and that local structural relaxations are associated with carbon additions. Possible implications of these ternary carbides for novel applications in steel design and manufacturing are discussed.@en

We have developed a nanoreactor, sample holder and gas system for in-situ transmission electron microscopy (TEM) of hydrogen storage materials up to at least 4.5 bar. The MEMS-based nanoreactor has a microheater, two electron-transparent windows and a gas inlet and outlet. The holder contains various O-rings to have leak-tight connections with the nanoreactor. The system was tested with the (de)hydrogenation of Pd at pressures up to 9.5 bar. The Pd film consisted of islands being 15 nm thick and 50-500 nm wide. In electron diffraction mode we observed reproducibly a crystal lattice expansion and shrinkage owing to hydrogenation and dehydrogenation, respectively. In selected-area electron diffraction and bright/dark-field modes the (de)hydrogenation of individual Pd particles was followed. Some Pd islands are consistently hydrogenated faster than others. When thermally cycled, thermal hysteresis of about 10-16 degrees C between hydrogen absorption and desorption was observed for hydrogen pressures of 0.5-4.5 bar. Experiments at 0.8 bar and 3.2 bar showed that the (de)hydrogenation temperature is not affected by the electron beam. This result shows that this is a fast method to investigate hydrogen storage materials with information at the nanometer scale.@en

Transmission electron microscopy (TEM) of (de-)hydrogenation reactions is crucial to characterize efficiency of hydrogen storage materials. The nanoreactor, a micromachined channel with 15-nm-thick windows, effectively confines the gas flow to an electron-transparent chamber during TEM of reactions. Realistic experiments require very high pressures to be sustained by the device. Nanomechanical bulge tests and simulations show that due to a very strong size effect, ultra-thin device components can reliably withstand tensile stresses as high as 19.5¿GPa enabling high pressure operation. We use the device to characterize Pd particles under a 4-bar H2 pressure within the ultra-high-vacuum of the TEM@en