Open Access

Melanins are organic, dark pigments produced by many organisms. Fungi either fix these pigments in their cell wall or secrete them into their environment to protect themselves against an array of physicochemical stresses (e.g., UV irradiation, desiccation, ...). However, melanins can also adsorb metals like iron and therefore might have a role in the fungal capacity to deteriorate iron-containing minerals and metals. To study this, we focus on the fungi Knufia petricola, a rock-inhabiting fungus with melanised cell walls which deteriorates minerals, and Amorphotheca resinae, a soil-borne fungus able to secrete melanin, degrade alkane-containing fuels, and corrode metals. The broader significance of this work lies in the mitigation of climate change via the negative emission technology enhanced rock weathering for the former to the mitigation of corrosion of biofuel infrastructure for the latter. Genes of K. petricola involved in melanin synthesis and iron uptake were deleted and down- and up- regulated to generate strains with a different melanin content and ability to take up iron. These strains and the wild type (WT) were exposed to a growth solution containing the iron-magnesium silicate olivine of which dissolution rates were obtained by measuring aqueous Mg concentrations using ICP-OES. Thus, the specific mineral deterioration mechanisms of melanised fungi were identified. Abiotically, these experiments showed that iron oxidation at the surface inhibits olivine dissolution. K. petricola was able to enhance dissolution when this abiotic inhibition is strongest (at pH 6) but prevented dissolution when this inhibition is weakest (at pH 4). The fungus therefore dissolves olivine by interacting with the oxidised iron at the olivine surface. Its iron uptake pathways do not seem to be involved as mutants deficient in iron uptake dissolved olivine at the same rate as the WT. The higher dissolution rates of a mutant which secretes a melanin precursor and the lower rates of a melanin-deficient mutant, however, indicate that the iron-adsorbing and -reducing capacities of melanin play a key role. This hypothesis is further supported by carbon steel corrosion experiments with six strains of A. resinae isolated from anthropogenic and natural environments. Their varying ability to secrete melanin correlated with their corrosion rates. We now plan to develop CRISPR/Cas9-mediated genome editing techniques for A. resinae to figure out whether this correlation is also a causation. In summary, our data show that the iron-binding capacity of melanins enables fungi to deteriorate iron-containing substrates at a higher rate.

This contribution presents the results of an experimental study on the creep behavior of an austenitic 316L stainless steel produced by laser powder bed fusion (PBF-LB/M/316L) with an emphasis on understanding the effects of microstructure on the creep mechanisms. Hot tensile tests and constant force creep tests at 600 °C and 650 °C, X-ray computed tomography, as well as optical and electron microscopy were performed. The produced PBF-LB/M/316L exhibits a low void population (< 0.01 %) resulting from the manufacturing parameters used and which allowed us to understand the effects of other microstructural aspects on creep behavior, e.g., grain morphology and dislocation substructure. A hot‑rolled variant of 316L was also tested as a reference.

For prestressing steel’s factory production control, approvals, and continuous surveillance in Germany, a susceptibility test against hydrogen-induced stress corrosion cracking is performed. The measured time to fracture results (in hours) must be reproducible and reliable in the test. ISO 15630-3 gives currently unpersuasive and diverging results using a free corrosion approach for hydrogen charging. A newly developed test method uses cathodic polarization for defined hydrogen charging instead of an uncontrolled and variable electron supply by metal dissolution during free corrosion. With this new test method, a reliable differentiation is possible between highly susceptible-known “old-type” quenched and tempered prestressing steel, i.e., Neptun, Hennigsdorfer, Sigma, and currently approved cold-drawn wires St 1470/1670 (CDS-1670) and St 1570/1770 (CDS-1770). The reproducibility of the new test method was evaluated in a round-robin test with eight attended testing institutes on a St 1470/1670 (CDS-1670) batch.

Digitalization is nowadays the central key in developing pharmaceutical products, but it also becomes increasingly important in computer aided material development. In this work it is presented how a collaborative ontology development for the alloy development process is approached and a workflow for chemical optimization of copper alloys is introduced. This is done by employing a combination of a high-throughput alloy development method [1] with the calculation of the corresponding phase compositions. The work presented here is part of the publicly funded project KupferDigital. The project is associated with the innovation platform MaterialDigital (PMD) and focusses on the digitalization of processes as well as knowledge representation along the life-cycle of copper and copper alloys. One part of this life cycle is the alloy development of copper alloys, in this case the alloy development employing a high throughput method based on diffusion couples. The alloy development process can be further broken down into several typical material processing steps such as casting, diffusion welding and annealing. As part of the copper life cycle, the constitution and the properties of an alloy play an important role for processes further down the road during product manufacturing and service life and are also crucial for the recycling properties of the alloy. It is therefore important to, on the one hand, communicate data concerning properties, process history and constitution to the following stations of the life cycle, on the other hand, it is also elementary for the material scientist to be aware of the recycling properties of the alloys constituents. This motivates sharing of data along the life cycle and the development of ontology based data spaces, where life-cycle information can be linked across all involved domains. As part of the alloy development process, it is presented how experimental data created at fem are shared using linked data and ontologies with an example based on the digital representation of the chemical composition of copper alloys further processed by CALculation of PHAse Diagrams (CALPHAD) at the Fraunhofer IWM. The calculation results are used to correlate measured hardness data with the equilibrium phases of the alloys. Selected Compositions are cast and heat treated and subjected to mechanical testing at BAM and the resulting mechanical property-data are again linked to the measured and simulated data from the alloy development process.

This publication is the final report on the proficiency test (PT) LS BAM-5.4-2024 „Measurement of the particle size distribution of ceramic powders by laser diffraction”. The PT was organized by the Federal Institute for Materials Research and Testing (BAM), division 5.4 “Advanced Multi-materials Processing”, Germany. The measurements took place from 2024/05 to 2024/07. The aim of the interlaboratory comparison was the proficiency assessment of the participating laboratories. The PT was performed in accordance with DIN EN ISO/IEC 17043:2010. The harmonized measurement procedure was based on ISO 13320:2020The statistical analysis was performed in accordance with DIN ISO 13528:2020 by use of the software PROLab (QuoData GmbH, Dresden, Germany). A group of 35 laboratories from 14 countries participated in the PT. Laser diffraction analyzers produced by 7 different manufacturers were used. The three test materials were commercial ceramic powders. Overall, the measured characteristic values of the particle size distributions (d10,3, d50,3 and d90,3) were in the size range between 1 and 35 μm. The final report contains all individual results in an anonymous form.