Influence of Processing Route on the Surface Reactivity of Cu47Ti33Zr11Ni6Sn2Si1 Metallic Glass

Recently, laser additive manufacturing (AM) techniques have emerged as a promising alternative for the synthesis of bulk metallic glasses (BMGs) with massively increased freedom in part size and geometry, thus extending their economic applicability of this material class. Nevertheless, porosity, compositional inhomogeneity, and crystallization display themselves to be the emerging challenges for this processing route. The impact of these “defects” on the surface reactivity and susceptibility to corrosion was seldom investigated but is critical for the further development of 3D-printed BMGs. This work compares the surface reactivity of cast and additively manufactured (via laser powder bed fusion—LPBF) Cu47Ti33Zr11Ni6Sn2Si1 metallic glass after 21 days of immersion in a corrosive HCl solution. The cast material presents lower oxygen content, homogeneous chemical distribution of the main elements, and the surface remains unaffected after the corrosion experimentation based on vertical scanning interferometry (VSI) investigation. On the contrary, the LPBF material presents a considerably higher reactivity seen through crack propagations on the surface. It exhibits higher oxygen content, heterogeneous chemical distribution, and presence of defects (porosity and cracks) generated during the manufacturing process

Multidisciplinary Diagnostic Algorithm for Evaluation of Patients Presenting with a Prosthetic Problem in the Hip or Knee:A Prospective Study

The predominant indications for revision surgery after total hip (THA) or knee arthroplasty (TKA) are an aseptic failure (AF) and prosthetic joint infection (PJI). Accurate diagnosis is crucial. Therefore, we evaluated prospectively a multidisciplinary diagnostic algorithm including multi-modal radionucleid imaging (RNI) and extended microbiological diagnostics. If the surgeon suspected PJI or AF, revision surgery was performed with multiple samples obtained in parallel for special culture procedures and later molecular analyses. Alternatively, if the underlying cause was not evident, RNI was scheduled comprising 99Tc—HDP SPECT/CT, 111In-labeled white blood cells combined with 99Tc-nanocoll bone marrow SPECT/CT, and 18F-FDG PET/CT. A multidisciplinary clinical team made a recommendation on the indication for a diagnostic procedure guided by RNI images or revision surgery. A total of 156 patients with 163 arthroplasties were included. Fifty-five patients underwent RNI. In all, 118 revision surgeries were performed in 112 patients: 71 on the indication of AF and 41 revision of PJI. Thirty-four patients were concluded with chronic pain, and revision surgery refrained. The effective median follow-up period was 13 months. A structured approach offered by the algorithm was useful for the clinician in the evaluation of patients with a failing TKA or THA. Surgical revision was possibly obviated in approximately 20% of patients where an explanation or cause of failure was not found. The algorithm served as an effective tool

Differential contributions of specimen types, culturing, and 16S rRNA sequencing in diagnosis of prosthetic joint infections

ABSTRACT Prosthetic joint failure is mainly caused by infection, aseptic failure (AF), and mechanical problems. Infection detection has been improved with modified culture methods and molecular diagnostics. However, comparisons between modified and conventional microbiology methods are difficult due to variations in specimen sampling. In this prospective, multidisciplinary study of hip or knee prosthetic failures, we assessed the contributions of different specimen types, extended culture incubations, and 16S rRNA sequencing for diagnosing prosthetic joint infections (PJI). Project specimens included joint fluid (JF), bone biopsy specimens (BB), soft-tissue biopsy specimens (STB), and swabs (SW) from the prosthesis, collected in situ , and sonication fluid collected from prosthetic components (PC). Specimens were cultured for 6 (conventional) or 14 days, and 16S rRNA sequencing was performed at study completion. Of the 156 patients enrolled, 111 underwent 114 surgical revisions (cases) due to indications of either PJI ( n = 43) or AF ( n = 71). Conventional tissue biopsy cultures confirmed PJI in 28/43 (65%) cases and refuted AF in 3/71 (4%) cases; one case was not evaluable. Based on these results, minor diagnostic adjustments were made. Fourteen-day cultures of JF, STB, and PC specimens confirmed PJI in 39/42 (93%) cases, and 16S rRNA sequencing confirmed PJI in 33/42 (83%) cases. One PJI case was confirmed with 16S rRNA sequencing alone and five with cultures of project specimens alone. These findings indicated that JF, STB, and PC specimen cultures qualified as an optimal diagnostic set. The contribution of sequencing to diagnosis of PJI may depend on patient selection; this hypothesis requires further investigation. </jats:p

Raw data topographic measurements by Raman spectroscopy-coupled vertical scanning interferometry-measurements (R-VSI) of corroded steel surface

The corrosion and degradation of materials, such as pipeline steel, have a strong effect on both the environment and the economy. The quantification of these processes can therefore provide important information needed to manage their impact. In this study, a concept for the characterization and quantification of corrosion is demonstrated on API X70 steel immersed in 3.5 wt.% NaCl solution. Due to the difficulty of quantifying corrosion rates, e.g., through single mean values, a unique system is applied that directly couples Raman spectroscopy with vertical scanning interferometry to assess the physical and chemical aspects of steel corrosion kinetics. Vertical scanning interferometry allows the quantification of the topographical evolution of corrosion product formation and material dissolution in combination with the direct measurements of the respective rates. The Raman spectroscopy provides additional information about the (mineral) phases. Rate variations ranging from uniform corrosion to areas of high pit densities are quantified and analyzed in rate maps and subsequently visualized in rate spectra. The rate distribution is classified into different domains and pitting rates. Thus, a comprehensive quantitative assessment of the characteristic corrosion behavior is discussed

Direct Observation of Microbial Inhibition of Calcite Dissolution

Vertical scanning interferometry (VSI) provides a method for quantification of surface topography at the angstrom to nanometer level. Time-dependent VSI measurements can be used to study the surface-normal retreat across crystal and other solid surfaces during dissolution or corrosion processes. Therefore, VSI can be used to directly and nondestructively measure mineral dissolution rates with high precision. We have used this method to compare the abiotic dissolution behavior of a representative calcite (CaCO(3)) cleavage face with that observed upon addition of an environmental microbe, Shewanella oneidensis MR-1, to the crystal surface. From our direct observations, we have concluded that the presence of the microbes results in a significant inhibition of the rate of calcite dissolution. This inhibition appears to be a 2nd-order effect that is related to the formation of etch pits. The opening of etch pits was greatly inhibited in the presence of added bacteria, suggesting that the bacterial cells exert their effect by inhibiting the formation of etch pits at high-energy sites at the crystal surface caused by lattice defects, e.g., screw or point dislocations. The experimental methodology thus provides a nondestructive, directly quantifiable, and easily visualized view of the interactions of microbes and minerals during weathering (or corrosion) processes or during mineral precipitation

Dissolution rate spectra data of calcite single crystal and micrite material

The large discrepancy between field and laboratory measurements of mineral reaction rates is a long-standing problem in earth sciences, often attributed to factors extrinsic to the mineral itself. Nevertheless, differences in reaction rate are also observed within laboratory measurements, raising the possibility of intrinsic variations as well. Critical insight is available from analysis of the relationship between the reaction rate and its distribution over the mineral surface. This analysis recognizes the fundamental variance of the rate. The resulting anisotropic rate distributions are completely obscured by the common practice of surface area normalization. In a simple experiment using a single crystal and its polycrystalline counterpart, we demonstrate the sensitivity of dissolution rate to grain size, results that undermine the use of "classical" rate constants. Comparison of selected published crystal surface step retreat velocities (Jordan and Rammensee, 1998) as well as large single crystal dissolution data (Busenberg and Plummer, 1986) provide further evidence of this fundamental variability. Our key finding highlights the unsubstantiated use of a single-valued "mean" rate or rate constant as a function of environmental conditions. Reactivity predictions and long-term reservoir stability calculations based on laboratory measurements are thus not directly applicable to natural settings without a probabilistic approach. Such a probabilistic approach must incorporate both the variation of surface energy as a general range (intrinsic variation) as well as constraints to this variation owing to the heterogeneity of complex material (e.g., density of domain borders). We suggest the introduction of surface energy spectra (or the resulting rate spectra) containing information about the probability of existing rate ranges and the critical modes of surface energy

Investigation of the influence of fluid flow on the mass transport of dissolved calcite ions on the microscale using 3D numerical simulation

The study and understanding of material dissolution plays an important role in environmental sciences, e.g. in the study of pipeline corrosion, reservoir development or nuclear waste storage. Commonly laboratory based experiments or numerical simulations in the meter scale are carried out to verify the resistivity of a material with regard to corrosion. However, it is challenging to directly determine the influence of the fluid movement on the relation of advective and diffusive mass transport on the µm scale. In order to overcome this difficulty we use a 3D numerical hydrodynamic continuum model by which the fluid flow and the mass transport over a pyrochlore surface are simulated. Using the finite volume method implemented in the open-source software CFD-package OpenFOAM, we investigated the hydrodynamic flow over three pyrochlore surfaces of varying surface roughness under steady-state flow conditions. The mass transport over the surfaced was further computed using the steady-state flow field. As may be expected the diffusive transport appeared to become lower with increasing flow velocity, but interestingly also as the surface roughness increased. Apart from that, we observed typical fluid dynamical features like the development of cavity flows in the surface depressions. Although the transport simulations show no influence of these hydrodynamic features, the mass transport changes with the flow velocity and surface roughness, with a higher release of dissolved calcite ions being observed at lower velocities and a lower surface roughness. Comment: The data in these archives contains case file for numerical studies in OpenFOAM to investigate the scope described above. Archives are split between three different surface topographies. The fourth archive contains data from post-processing