Mechanical, Corrosive, and Tribological Degradation of Metal Coatings and Modified Metallic Surfaces

Mechanical, corrosive, and tribological degradation of metal and metal coatings is just one of the challenges faced by numerous industries [...

Unravelling the Role of Nitrogen in Surface Chemistry and Oxidation Evolution of Deep Cryogenic Treated High-Alloyed Ferrous Alloy

The role of nitrogen, introduced by deep cryogenic treatment (DCT), has been investigated and unraveled in relation to induced surface chemistry changes and improved corrosion resistance of high-alloyed ferrous alloy AISI M35. The assumptions and observations of the role of nitrogen were investigated and confirmed by using a multitude of complementary investigation techniques with a strong emphasis on ToF-SIMS. DCT samples display modified thickness, composition and layering structure of the corrosion products and passive film compared to a conventionally heat-treated sample under the same environmental conditions. The changes in the passive film composition of a DCT sample is correlated to the presence of the so-called ghost layer, which has higher concentration of nitrogen. This layer acts as a precursor for the formation of green rust on which magnetite is formed. This specific layer combination acts as an effective protective barrier against material degradation. The dynamics of oxide layer build-up is also changed by DCT, which is elucidated by the detection of different metallic ions and their modified distribution over surface thickness compared to its CHT counterpart. Newly observed passive film induced by DCT successfully overcomes the testing conditions in more extreme environments such as high temperature and vibrations, which additionally confirms the improved corrosion resistance of DCT treated high-alloyed ferrous alloys

Influence of the Deep Cryogenic Treatment on AISI 52100 and AISI D3 Steel’s Corrosion Resistance

The effect of deep cryogenic treatment (DCT) on corrosion resistance of steels AISI 52100 and AISI D3 is investigated and compared with conventional heat-treated counterparts. DCT’s influence on microstructural changes is subsequently correlated to the corrosion resistance. DCT is confirmed to reduce the formation of corrosion products on steels’ surface, retard the corrosion products development and propagation. DCT reduces surface cracking, which is considered to be related to modified residual stress state of the material. DCT’s influence on each steel results from the altered microstructure and alloying element concentration that depends on steel matrix and type. This study presents DCT as an effective method for corrosion resistance alteration of steels

Mechanical limits of viral capsids

We study the elastic properties and mechanical stability of viral capsids under external force-loading with computer simulations. Our approach allows the implementation of specific geometries corresponding to specific phages such as $\phi$29 and CCMV. We demonstrate how in a combined numerical and experimental approach the elastic parameters can be determined with high precision. The experimentally observed bimodality of elastic spring constants is shown to be of geometrical origin, namely the presence of pentavalent units in the viral shell. A criterion for capsid breakage is defined, which explains well the experimentally observed rupture. From our numerics we find for the dependence of the rupture force on the F\"oppl-von K\'arm\'an (FvK) number a crossover from $\gamma^{2/3}$ to $\gamma^{1/2}$. For filled capsids high internal pressures lead to a stronger destabilization of viruses with a buckled ground state than unbuckled ones. Finally, we show how our numerically calculated energy maps can be used to extract information about the strength of protein-protein interactions from rupture experiments.Comment: 6 pages, 9 figure

Coupled role of alloying and manufacturing on deep cryogenic treatment performance on high-alloyed ferrous alloys

This study focuses on influence of alloying content and type of manufacturing on the effectiveness of deep cryogenic treatment (DCT) on properties of selected high-alloyed ferrous alloys (HAFA): EN HS6-5-2, EN HS6-5-2-5, EN HS6-5-3 and EN HS12-1-4. In order to evaluate the dependency of DCT performance on chemical composition and manufacturing type, the microstructure, hardness, impact and fracture toughness and fatigue properties were analyzed. Additionally, the fatigue data was evaluated using an adapted strain-life model in order to understand the unique effects of DCT with selected factors and provide a model for estimating the fatigue limit of DCT HAFA. The study indicates that DCT affects carbide precipitation, size and morphology of nanocarbides, average distance between carbides and nanocarbides, as well as the base matrix (martensitic laths). The induced microstructural changes cause an overall positive change of mechanical properties in selected HAFA, which correlates well with individual alloying and manufacturing differences. Overall, DCT has greater effect on wrought HAFA than powder metallurgy manufactured HAFA, at which high content of W and Co generally degenerates the DCT induced microstructure modifications

Macro- and micro-strain in GaN nanowires on Si(111)

We analyze the strain state of GaN nanowire ensembles by x-ray diffraction. The nanowires are grown by molecular beam epitaxy on a Si(111) substrate in a self-organized manner. On a macroscopic scale, the nanowires are found to be free of strain. However, coalescence of the nanowires results in micro-strain with a magnitude from +-0.015% to +-0.03%.This micro-strain contributes to the linewidth observed in low-temperature photoluminescence spectra