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On-line monitoring of polyhydroxyalkanoate extraction process using compact NMR spectroscopy
No full textPortable benchtop NMR spectrometers enable real-time process and reaction monitoring in contrast to conventional laboratory based off-line gas chromatography or high-field NMR measurements. In this study, benchtop NMR spectroscopy is demonstrated as a process analytical technology (PAT) tool for the application of the solvent extraction step in downstream processing of polyhydroxyalkanoate (PHA) biopolymers. These are one of the few thermoplastic polymers synthesized 100 % via biotechnological routes which fully biodegrade in common natural environments. This makes them excellent candidate materials for sustainable replacement of conventional plastic materials.
Online NMR experiments were conducted using a fully automated setup, employing commercially available PTFE tubing as a flow-cell assembly. Extraction was carried out in a thermostated stirred batch reactor in lab-scale. Single-scan NMR spectra allowed continuous monitoring of the extraction of the PHA copolymer poly-(hydroxybutyrate-co-hydroxyhexanoate) containing 13.5 mol-% hydroxyhexanoate from Ralstonia eutropha biomass. Extractions were performed in chloroform and acetone across ground lyophilized cell loadings ranging from 20 to 120 g/L. The reproducibility and reliability of compact NMR spectroscopy closely matched with high-field NMR measurements. A strong correlation was observed between online low-field NMR data and offline gas chromatography (GC) analysis. The study highlights the versatility of compact NMR for process monitoring, facilitating endpoint determination and enhancing extraction efficiency by optimizing process parameters. Steady-state conditions were achieved within 6 to 10 minutes for chloroform and acetone, respectively, underscoring the method’s value in supporting downstream process development and optimization for PHA recovery
X-ray absorption spectroscopy of scandium oxide polymorphs
No full textScandium oxide (Sc2O3) is a rare-earth oxide with significant potential in key technological areas, but due to its limited supply a deep understanding of its characteristics in different crystalline phases is still missing. Here, we present a combined experimental and ab initio X-ray absorption spectroscopy investigation of Sc2O3 focusing on excitations from the O K-edge and the Sc L2,3-edge. While measurements are performed on a cubic sample, the most stable phase under ambient conditions, six different polymorphs are computed, including two high-pressure phases with a trigonal and monoclinic lattice in addition to the cubic phase, as well as three computationally predicted structures. Our analysis of the structural and electronic properties reveals significant similarities between the cubic polymorph and the high-pressure trigonal phase, while the monoclinic crystal exhibits distinct features. The spectra simulated for these similar phases from the solution of the Bethe–Salpeter equation show very good agreement with measurements. Additional comparison with results computed in the independent-particle approximation highlights the dominant role of electron–hole correlations in shaping the absorption features, particularly at the O K-edge, where a common pattern with the features of other sesquioxides is identified. Our findings offer new insight into the spectral fingerprints of Sc2O3 polymorphs, aiding in situ characterization and informing sustainable materials management
A modular concept for protection against debris flight - Design, properties and usage
No full textWith advances in technological development, stationary and mobile storage units for compressed hydrogen are becoming larger and larger. Their number is also increasing. At the same time, their design has evolved from steel and aluminium to pressure vessels made of composite materials. For safety reasons the design approval of those composite cylinders requires fire engulfment tests, which are mainly organised as open-air tests always needs dedicated protection measures. Under some conditions those protections measures even reduce the effort for organisational safety measures if e.g. the emission of splinters can get totally prevented. Another aspect is the improved reproducibility of fire tests by reducing the influence of wind.
Between 2017 and 2019, BAM developed a stackable protective frame made of steel to safely capture splinters for the safe execution of high-energy impact tests. However, this frame was not flexible enough for the follow-up project, which led to a completely new protection concept for (potentially) destructive tests on gas-filled pressure vessels. This concept is based on very robust building blocks made from welded steel. Despite their considerable weight of around 500 kg p.p., they can be combined and stacked very easily like ‘Lego bricks’. The presentation will show the flexibility of the concept, some results of tests on the robustness against pressure waves and the effectiveness in wind attenuation. Finally, the interaction with a new, also modular burner concept for localised fires and full engulfment fires will be presented
Recycling nickel aluminium bronze grinding chips to feedstock for directed energy deposition via impact whirl milling: Investigation on processability, microstructure and mechanical properties
No full textDuring the production of ship propellers, considerable quantities of grinding chips from nickel aluminium bronze areproduced. This paper examines the mechanical comminution of such chips via impact whirl milling and the utilization of twochip-powder batches as feedstock for a laser-based directed energy deposition process. The materials are characterized viadigital image analysis, standardized flowability tests, scanning electron microscopy and energy dispersive X-ray spectroscopyand are compared to conventional, gas atomized powder. The specimens deposited via directed energy deposition areanalyzed for density, hardness and microstructure and tensile properties for vertical and horizontal build up directions arecompared. At elevated mill rotation speeds, the comminution with impact whirl milling produced rounded particles, favorableflow properties and particle size distribution, making them suitable to deposit additive specimens. The microstructureexhibited characteristic martensitic phases due to the high cooling rates of the additive manufacturing process. The presenceof ceramic inclusions was observed in both the powder and on the tensile fracture surfaces, partly impairing the mechanicalproperties. However, specimens in the vertical build-up direction (Z) showed competitive tensile results, with 775 MPa intensile strength, 455 MPa in yield strength and 12.6 % elongation at break. The findings of this study indicate that recyclingof machining chips to additive manufacturing feedstock can be a viable option for reducing material costs and environmentalimpact
Precise Real‐Time Measurement of Liquid Viscosity Using Digital Video Data
No full textQuantitative knowledge of liquid viscosity is of fundamental importance in many areas of materials synthesis and processing. However, the determination of viscosity often relies on specialized experimental equipment, offline experimentation, or invasive procedures, in particular when required in extreme conditions such as at high temperature, high pressure, and in confined or corrosive environments. Here, this study proposes and validates a fast and simple method that mimics the intuitive perception of liquid flow within a quantitative framework. For this, this study employs digital video observation to derive quantitative values of the shear viscosity of liquids, with high precision and rapid acquisition rates. The technique involves capturing liquid dynamics after minor mechanical stimulation. Processed imaging data are indexed by similarity and referenced to a digital database generated with a finite element model, from which values of viscosity are obtained in line. The approach is tested on water at room temperature and on a high‐temperature glass melt. Covering a viscosity range of four orders of magnitude, both yield convincing agreement with tabulated reference data at low computational cost
Internal friction and energy dissipation during fracture in silicate glasses
No full textTo obtain a deeper insight into the nature of energy dissipation during fracture, the internal friction of 13 borosilicate, aluminosilicate, soda-lime, and lead-containing glasses, for which inert crack growth data are known, was measured using dynamic mechanical thermal analysis. For asymmetrically bent glass beams, the loss tangent, tan δ, was determined between 0.2 and 50 Hz at temperatures between 273 K and the glass transition temperature, Tg. It was found that the area under the tan δ vs T·Tg−1 curve correlates with the crack growth exponent, n, in the empirical v = v0·KIn relation between crack growth velocity, v, and stress intensity, KI, which indicates that n correlates with the degree of energy dissipation of sub-Tg relaxation phenomena
Wear resistance of modified Ni based claddings in relation to the resulting machinability via ultrasonic-assisted milling
No full textIn the field of plastics processing, extruder screws are subjected to significant wear stresses. The extruder screw is the main wear component in those production machines and is usually coated with intermetallic wear protection alloys composed of Ni-based alloys, specifically Colmonoy C56 PTA (NiMoCrSi). There is a growing demand for providing an economic machinability of these alloys to achieve defined contours with a sufficient surface integrity. Recent investigations exhibit promising results applying ultrasonic milling for such hard-to-cut materials. The Colmonoy C56 is modified by various alloying additions Ti, Nb, Mo, Hf, and Al, and then cladded on a steel S355 via Plasma Transferred Arc process. The effect of alloying additions on the microstructure is analyzed regarding their resistance to abrasive and adhesive wear. With Miller test ASTM G75 the influence of alloying elements on resistance to abrasive wear for two abrasive materials is investigated (high-grade corundum F220 and quartz powder). The wear loss is not increased for additions of Nb and Ti compared to the base material C56. Modifications with Hf or Al reduces the resistance to abrasive wear and significantly increases material loss. The extruder screw is also subject to adhesive wear, which can be quantified by means of the pin-roll test. It is demonstrated that the addition of Hf, for example, contributes to a reduction in wear loss. Aim of the investigations is to find suitable modifications for the wear claddings of C56 for a sufficient machineability, without compemising the wear resistant. The machinability is considerably affected by the alloy additions, and is determined using ultrasonic-assisted milling. The addition of hafnium reduces machinability, i.e. significantly increases cutting forces. The incorporation of Nb exhibits a significant reduction of cutting forces, and results in reduced tool wear and an enhanced of surface integrity (roughness, density of defects, residual stresses)
Energy conversion of waste heat using thermomagnetic materials
No full textTo date, there are very few technologies available for the conversion of low-temperature waste heat into electricity. Thermomagnetic generators are one approach proposed more than a century ago. Such devices are based on a cyclic change of magnetization with temperature. This switches a magnetic flux and, according to Faraday’s law, induces a voltage. We demonstrated that guiding the magnetic flux with a pretzel-type topology of the magnetic circuit improves the performance of thermomagnetic generators by orders of magnitude [1]. From an ideal material’s perspective, several similarities with magnetocaloric materials [2] can be found, like a sharp first-order like magnetostructural transition, low hysteresis and high thermal diffusivity. This makes some magnetocaloric materials good candidates also for thermomagnetic energy harvesting, like e.g. (MnFe)2P-based and La(Fe,Si)13-based compounds.
Recently, the EU MSCA initial training network Heat4Energy [2] was started with the aim of making three thermomagnetic energy converters for low grade waste heat (<100°C) to electricity with different power output ranges. While the smallest demonstrator operates with thin film materials, the two larger machines use bulk material, for which different processing and shaping routes are explored. In collaboration with the industrial stakeholders of the project, up-scalability and practical application issues of materials processing will be addressed during the project. After an introduction into the technological background and the ITN project, we will present first results on 3D printing and non-destructive imaging of the thermomagnetic parts. Furthermore, we will review criticality issues of materials employed in this new technology
Resolving the Subsurface Residual Stress Maximum in Laser Powder Bed-Fused 316L Stainless Steel by Diffraction-Based Analysis
No full textLaser powder bed fusion (PBF-LB/M) is a metal additive manufacturing process. Due to the complex nature of the layer-wise, repeated heating and cooling cycles, it tends to generate high-magnitude residual stresses. If not correctly understood and mitigated through in- or post-process approaches, these residual stresses can be detrimental as they are often tensile at the surface. However, determining the magnitude and location of peak tensile residual stresses is not trivial as they are often located subsurface. This work focuses on determining the magnitude and location of these deleterious tensile residual stresses in a PBF-LB/316L specimen. Two diffraction-based Methods are used to reveal the relationship between the residual stresses and the underlying microstructure. On the one hand, high spatial resolution Neutron diffraction is used to determine triaxial stresses from the bulk to a depth of 0.15 mm. On the other hand, laboratory X-ray diffraction coupled with electrolytical layer removal allows the biaxial residual stress depth profile to be probed from the surface to a depth of about 0.6 mm. The results show a good agreement between the two methods. The peak residual stress is shown to be 500 MPa, which appears as a plateau between 0.08 and 0.35 mm in depth
Safety for H2 Transport in Welded Low-Alloy Gas Pipelines
No full textSteel gas pipelines are to be used in the future for the transport of hydrogen (H) or for its blending in natural gas. For the use of existing pipeline systems, as well as their adaptation and expansion with modern steels to the end user, it is necessary to investigate the extent to which hydrogen is absorbed by the material or welded joints, depending on the gas composition and changing temperature and pressure stresses, and can reduce their ductility, in order to exclude an unexpected brittle failure in the form of hydrogen-assisted cracking. So far, in-situ tests of H-absorption under continuous mechanical stress have been carried out using slow strain rate tests (SSRT) with full-section test specimens in high-pressure autoclaves. The high safetyrelated laboratory costs associated with this prevent cost-effective series testing for industry. Initial studies show that hollow tensile specimens (HTS) SSRT are a viable alternative through the defined adjustment of gases and pressures via the inner bore hole. To this end, the following key questions need to be addressed, (1) representation of real stress scenarios of welded pipes on HTS, (2) the effect of the gas composition (H2/CH4) on H absorption and degradation, (3) the influences and interaction of different weld seam structures under continuous and cyclically changing stress, (4) the possibility of integrating into a practical test concept for the evaluation of welded steels, and (5) the material behaviour of existing pipelines compared to modern steels. This work, which is being carried out as part of the IGF project no. 22884, focuses on a systematic investigation of the boundary conditions temperature, pressure and H2 partial pressure as well as steel grade and strain rate in correlation with realistic conditions. The experimental investigations show significant, and in dependence of the strain rate, different pronounced effects, in particular due to the temperature and the H2 partial pressure on the deformation capacity of the examined materials. With this, the technology should be further developed for further questions, in particular with regard to weld microstructure, in order to establish a simple, economical test procedure based on HZP-SSRT with regard to the H-readiness of welded steel pipelines by means of corresponding guidelines and transfer to standards. Ultimately, users, especially SMEs such as testing laboratories, should be involved in the development of the hydrogen economy as part of the energy transition, which underlines the high relevance for society as a whole