Alloying of refractory high entropy alloys (HEAs) such as MoNbTaW is usually done by vacuum arc melting (VAM) or powder metallurgy (PM) due to the high melting points of the elements. Machining to produce the final shape of parts is often needed after the PM process. Casting processes, which are often used for aerospace components (turbine blades, vanes), are not possible. Direct metal deposition (DMD) is an additive manufacturing technique used for the refurbishment of superalloy components, but generating these components from the bottom up is also of current research interest. MoNbTaW possesses high yield strength at high temperatures and could be an alternative to state-of-the-art materials. In this study, DMD of an equimolar mixture of elemental powders was performed with a pulsed Nd:YAG laser. Single wall structures were built, deposition strategies developed and the microstructure of MoNbTaW was analyzed by back scattered electrons (BSE) and energy dispersive X-ray (EDX) spectroscopy in a scanning electron microscope. DMD enables the generation of composition gradients by using dynamic powder mixing instead of pre-alloyed powders. However, the simultaneous handling of several elemental or pre-alloyed powders brings new challenges to the deposition process. The influence of thermal properties, melting point and vapor pressure on the deposition process and chemical composition will be discussed

This article reports about nanocomposites, which refractive index is tuned by adding TiO₂ nanoparticles. We compare in situ/ex situ preparation of nanocomposites. Preparation procedure is described, properties of nanocomposites are compared, and especially we examine the applicability of two-photon polymerization (2PP) of synthesized nanocomposites. All prepared samples exhibit suitable optical transparency at specific laser wavelengths. Three-dimensional structures were generated by means of two-photon polymerization effect induced by a femtosecond laser.

We report on the first experimental observation of a concentric-ring pattern in a short planar dielectric barrier gas-discharge system and study its spatiotemporal behavior. While increasing the gas pressure the destabilization of the rings into a filamentary structure is observed. The charge carriers deposited on the dielectric electrodes determine the spatiotemporal behavior of the pattern.