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DOE OSTI2016

Effective reduction in the nanoparticle sizes of NiO obtained via the pyrolysis of nickel malonate precursor modified using oleylamine surfactant

Nickel oxide nanoparticles were synthesized via thermal decomposition of two precursors, the first, a simple nickel malonate and the second, a nickel malonate modified by oleylamine, a surfactant, both having been synthesized by precipitation. While FTIR, TGA and ToF-SIMS were used to characterize the two precursors and to show the presence of oleylamine in the modified precursor, XRD, SEM, TEM and BET were employed to investigate the structure, the morphology and the specific surface area of the decomposition products obtained after pyrolysis. The results showed that the modification of nickel malonate by oleylamine was effective. The XRD results, which showed a cubic structure for the NiO obtained, suggest with SEM an important particle size reduction (at least 54%) when oleylamine was used to modify the nickel malonate precursor. The SEM images also showed a well-defined spherical nanoparticle morphology in both cases, not affected by the presence of oleylamine. The TEM also confirmed the reduction of particle size and their spherical nature but at the same time showed that, in the presence of oleylamine, there was no agglomeration resulting in a more uniform particle size distribution. The specific surface area of the NiO obtained by the oleylamine-modified precursor was 4.7 times larger than that obtained with the regular precursor. This again confirms the particle size reduction. - Highlights: • Nickel malonate precursor has been synthesized by precipitation method. • This precursor was successfully modified by a surfactant (oleylamine). • NiO was identified as the decomposition products of the previous precursors. • Oleylamine has provoked around 54% of particle size reduction of the NiO.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

Physicochemical and antibacterial characterization of ionocity Ag/Cu powder nanoparticles

Metal ion in bimetallic nanoparticles has shown vast potential in a variety of applications. In this paper we show the results of physical and chemical investigations of powder Ag/Cu nanoparticles obtained by chemical synthesis. Transmission electron microscopy (TEM) experiment indicated the presence of bimetallic nanoparticles in the agglomerated form. The average size of silver and copper nanoparticles is 17.1(4) nm (Ag) and 28.9(2) nm (Cu) basing on the X-ray diffraction (XRD) data. X-ray photoelectron (XPS) and Raman spectroscopies revealed the existence of metallic silver and copper as well as Cu{sub 2}O and CuO being a part of the nanoparticles. Moreover, UV–Vis spectroscopy showed surface alloy of Ag and Cu while Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) and Energy Dispersive X-ray Spectroscopy (EDX) showed heterogeneously distributed Ag structures placed on spherical Cu nanoparticles. The tests of antibacterial activity show promising killing/inhibiting growth behaviour for Gram positive and Gram negative bacteria. - Highlights: • Ag/Cu nanoparticles were obtained in the powder form. • The average size of nanoparticles is 17.1(4) nm (Ag) and 28.9(2) nm (Cu). • Ag/Cu powder nanoparticle shows promising antibacterial properties.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Effect of cold rolling on the microstructural evolution of new β-typed Ti–6Mo–6V–5Cr–3Sn–2.5Zr alloys

A Ti–6Mo–6V–5Cr–3Sn–2.5Zr (wt.%) alloy was designed as a new metastable β-Ti alloy. The effect that cold rolling had on the microstructural evolution of the material was investigated via optical microscopy (OM), X-ray diffraction (XRD), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM) measurements. A single β phase formed in the alloy after solution treatment at 780 °C for 30 min followed by water quenching. The solution-treated alloy was cold rolled with thickness reductions of 10%, 30%, 50% and 70%, and the hardness values increased as the thickness of the specimen decreased. The textures of the cold rolled specimen were characterized according to the 〈110〉 partial parallel to the rolling direction as the rolling reduction increased. The crystallographic orientation showed principal α-fiber textures for (111)〈110〉 and (112)〈110〉. The cold deformation led to the appearance of martensite α″ phases, particularly stress-induced martensite (SIM) α″ phases. - Highlights: • Effect of cold rolling on new β-typed Ti-6Mo-6V-5Cr-3Sn-2.5Zr alloy was studied. • A single β phase was obtained after solution treatment at 780 °C for 30 min. • α-Fiber textures became dominated with the increase in cold rolling reduction. • A stress-induced α″ martensite was caused by cold rolling.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Impact of microstructure on the thermoelectric properties of the ternary compound Ce{sub 3}Cu{sub 3}Sb{sub 4}

We present detailed structural and thermoelectric studies of the ternary compound Ce{sub 3}Cu{sub 3}Sb{sub 4}. This material is of interest due to previously reported considerable thermopower above room temperature (∼ 100 μV/K) and low thermal conductivity (2 W/(m K)). Here, we present detailed studies concerning microstructural and thermoelectric data, their variation across the samples and possible explanations for the observed behaviour. We have used X-ray diffraction, scanning electron microscopy (SEM), and time-of-flight secondary ion mass spectrometry (TOF-SIMS) for microstructural analysis. The thermoelectric properties were examined using a physical property measurement system (PPMS). We analyse the impact of the sample quality on the thermoelectric properties. The most unstable parameter is the material resistivity which varies between 1.5 and 15 mΩ cm at room temperature. The properties variability is mainly due to structural defects caused by stresses during material preparation and also due to formation of foreign phases CeCuSb{sub 2} and CeSb. The figure of merit ZT is also strongly dependent on the quality of the sample. The largest value ZT ≈ 0.15 at 400 K is determined for the almost stoichiometric sample with small amounts of a impurity phases. - Highlights: •The Ce{sub 3}Cu{sub 3}Sb{sub 4} has considerable thermoelectric properties and potential for further chemical and/or structural modification. •The control over foreign phases formation is challenging. •The defects arising during arc melting process highly deteriorate ZT of material.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Multilayered vacuum-arc nanocomposite TiN/ZrN coatings before and after annealing: Structure, properties, first-principles calculations

Highlights: • Multilayer TiN/ZrN films were deposited using sequential vacuum-arc deposition of Ti and Zr targets in nitrogen atmosphere; • Several samples were annealed in air at the temperature 700 °C; • First-principles calculations of TiN(111), ZrN(111) structures and TiN(111)/ZrN(111) multilayer were carried out; • All deposited samples were highly polycrystalline with quite large 20–25 nm crystals; • The nanohardness and elastic modulus of non-annealed coatings reached 42 GPa and 348 GPa, respectively; • Deposited coatings demonstrate good wear and oxidation resistance; - Abstract: Nanoscale multilayered TiN/ZrN films were deposited using sequential vacuum-arc deposition of Ti and Zr targets in a nitrogen atmosphere. Studies of film's properties were carried out using various modern methods of analysis, such as XRD, STEM, HRTEM, SIMS combined with results of nanoindentation and tribological tests. To interpret the mechanical properties of the deposited multilayer films first-principles calculations of TiN(111), ZrN(111) structures and TiN(111)/ZrN(111) multilayer were carried out. To study the influence of thermal annealing, several samples were annealed in air at the temperature 700 °C. All deposited samples were highly polycrystalline with quite large 20–25 nm crystals. The crystalline planes were very ordinated and demonstrated an excellent coordinated growth. The nanohardness and elastic modulus of non-annealed coatings reached 42 GPa and 348 GPa, respectively. Annealing in air at the temperature 700 °C led to partial oxidation of the multilayered coatings, however hardness of the non-oxidized part of the coatings remained as high, as for initial coatings. All deposited coatings demonstrate good wear resistance.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2018

Microstructural study and simulation of intrinsic two-way shape memory behavior of functionally graded Ni-rich/NiTiCu thin film

Highlights: • Ni-rich/Ti-rich bi-layer thin film was deposited on Si by using DC magnetron sputtering. • The bi-layer exhibits the gradient structure and mechanical properties through the thickness. • The bi-layer shows intrinsic two-way shape memory effect due to functionally graded structure. • The intrinsic two-way shape memory effect was confirmed by finite element simulation. - Abstract: In this research, the gradient structure and mechanical properties of an austenitic/martensitic (Ni{sub 50.8}Ti/Ni{sub 45}TiCu{sub 5} (at.%)) bi-layer thin film was investigated. The bi-layer was deposited on a Si substrate using DC magnetron sputtering. After crystallization of the film at 773 K for 60 min, the microstructure and mechanical properties of the bi-layer thin film were characterized using X-ray diffraction (XRD), transmission electron microscopy (STEM and HRTEM) and nanoindentation, respectively. The diffraction pattern illustrated that the crystallized bi-layer was combined of martensitic and austenitic layers while secondary ion mass spectroscopy (SIMS) and high resolution transmission electron microscopy analysis demonstrated the existence of a compositional gradient through the thickness and residual strain in the interface of the bi-layer, respectively. Furthermore, the compositional gradient in the bi-layer led to gradual variations in the structure, hardness and Young's modulus through the thickness of the bi-layer. The intrinsic two-way shape memory effect due to its functionally graded structure and the induced stress was confirmed by experimental test and finite element simulation.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Fabrication and characterization of a novel β metastable Ti-Mo-Zr alloy with large ductility and improved yield strength

Highlights: • Ti-12Mo-5Zr alloy exhibits excellent combination of improved yielding strength (>650 MPa), high ductility (uniform elongation ≈30%) and work-hardening behaviour. • The superior performances arise from the synergic effects between phase transformation induced plasticity and twinning induced plasticity. • The ‘d-electron’ alloy design approach in Ti-12Mo-5Zr alloy, i.e. Zr substitution to Ti, validates the feasibility of yielding stress improvement of TWIP/TRIP titanium alloys. - Abstract: In this paper, a novel ternary β-metastable titanium alloy, Ti-12Mo-5Zr (wt%), was designed based on the “d-electron” alloy design theory. The Ti-12Mo-5Zr alloy displays excellent combination of improved yielding stress (>650 MPa), high ductility (uniform elongation ≈30%) and work-hardening behaviour. The detailed microstructural analysis indicates that the superior performances arise from the synergic effects between phase transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP). Conforming to the design strategy, the improvement of mechanical performance results from the addition of Zr alloying element in substituting Ti, attributing to solution hardening effect and the increasing of critical resolved shear stress (CRSS) of stress induced martensitic transformation (SIM α″).

36 MATERIALS SCIENCE↗

DOE OSTI2018

Microstructure and texture evolution of duplex stainless steels with different molybdenum contents

Highlights: • The 3.05Mo steel has higher resistance to strain-induced transformation than the 0.28Mo steel. • The increased Mo content affects the grain growth of austenite and ferrite due to the effects of segregation and anchoring. • At high annealing temperatures, this Mo retarding effect is weakened. • The suppression of γ-fiber development in the ferrite texture is associated with the increased Mo content. • High amounts of Mo generate unfavorable conditions for the formation of CSL boundaries. - Abstract: The microstructure and texture evolution of duplex stainless steels with different molybdenum contents were studied. For this purpose, hot-rolled 2205 and 2304 samples were solution-annealed at 1100 °C for 1800 s and then cold-rolled to a 75% thickness reduction. This was followed by an isothermal annealing at 900 and 1100 °C for 180 s. The EBSD technique was used to determine the phase ratio, crystallographic texture, and microstructural characteristics. The hot-rolled steel had a work hardened microstructure and the samples submitted to intermediate annealing presented mainly deformation-free grains. Cold rolling resulted in a substantial reduction in the phase spacing with the formation of the strain-induced α′-martensite (SIM) from the metastable austenite. After annealing at 900 °C, the ferrite grains retained the elongated shape of the cold-rolled condition and the primary recrystallization progressed in the austenite phase. Increasing the Mo content increased the resistance to strain-induced martensitic transformation and inhibited the grain growth of austenite phase during annealing at 900 °C. Increasing annealing temperature to 1100 °C promoted the coarsening of both bcc and fcc structures with the formation of annealing twins in the austenitic grains. The recrystallization kinetics and subsequent grain growth occur earlier in ferrite than in austenite phase. Differences in Mo content did not significantly alter the evolution of austenite texture, whereas in the ferrite phase the increase in Mo content suppressed the γ-fiber development. Oriented nucleation was the predominant mechanism observed during the recrystallization of ferritic grains in the 2205 samples. The development of ∑19a boundaries was associated with the selected growth of {554}<225>{sub α} grains in the annealed 2304 samples. Annealing twins were associated with the formation of Σ3 boundaries after the heat treatments. Grain coarsening resulted in a larger fraction of the special boundaries in ferrite phase but inhibited the CSL formation in the austenite phase.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Detailed investigation of defect states in Erbium doped In2O3 thin films

Highlights: • SIMS analysis confirmed the doping of Er into the In{sub 2}O{sub 3} TF. • I–V loop analysis gives reduced current memory window for In{sub 2}O{sub 3}:Er TF based device. • High ideality factor was determined at low temperature and explained. • Defect related photoconductivity was confirmed from low temperature measurement. • 10 K temporal response of the Au/In{sub 2}O{sub 3}:Er/Si confirmed removal of oxygen defects. - Abstract: Erbium doped Indium Oxide (In{sub 2}O{sub 3}:Er) thin films (TFs) were synthesised by spin-on technique. Secondary Ion Mass Spectrometry confirmed that Er is incorporated into the In{sub 2}O{sub 3} lattice and formed an In-O-Er layer. The current–voltage loop produced a lower loop current window of ∼3.6 × 10{sup −4} A for In{sub 2}O{sub 3}:Er TF based devices. The Au/In{sub 2}O{sub 3}:Er/Si Schottky devices have lower ideality factor (∼6) and higher barrier height (∼0.63 eV) at 300 K than Au/In{sub 2}O{sub 3}/Si control samples. A blue shift in the main band-gap (∼50 nm) was calculated for In{sub 2}O{sub 3}:Er TFs from 10 K photoresponse. The Au/In{sub 2}O{sub 3}:Er/Si samples show higher photosensitivity in the temperature range 10 K–300 K and maximum (∼15 times) in the UV region at 10 K as compared to the Au/In{sub 2}O{sub 3}/Si devices. In addition, the Au/In{sub 2}O{sub 3}:Er/Si devices have better UV to visible cut-off ratio (∼3 times). Excellent temporal responses were recorded for Au/In{sub 2}O{sub 3}:Er/Si in the UV region as compared to Au/In{sub 2}O{sub 3}/Si.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2020

The CLAS12 Micromegas Vertex Tracker

The Micromegas Vertex Tracker was designed to improve upon the tracking capabilities of the baseline design of the CLAS12 spectrometer in Hall~B at Jefferson Laboratory. A Barrel Micromegas Tracker made with six concentric cylinders, each made of three 120$^\circ$-sector tiles, surrounds the Silicon Vertex Tracker, and a Forward Micromegas Tracker composed of 6 disks is placed 30~cm downstream of the liquid-hydrogen target. Both trackers sit in a 5~T solenoid magnetic field. All Micromegas elements are based on resistive technology to withstand luminosities up to $10^{35}$~cm$^{-2}$s$^{-1}$, as well as on bulk technology to enforce gain uniformity and mechanical robustness. Due to the high magnetic field, dedicated electronics have been designed and displaced $\sim$2~m away from the detectors. The electronics readout is based on the DREAM ASICs that allow sustained operation up to 20~kHz trigger rate at the maximum luminosity.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2020

Single electron–hole pair sensitive silicon detector with surface event discrimination

Here, we demonstrate single electron-hole pair resolution in a single-sided, contact-free 1 cm$^2$ by 1 mm thick Si crystal operated at 48 mK, with a baseline energy resolution of 3 eV. This crystal can be operated at voltages in excess of $\pm50$ V, resulting in a measured charge resolution of 0.06 electron-hole pairs. The high aluminum coverage ($\sim$70%) of this device allows for the discrimination of surface events and separation of events occurring near the center of the detector from those near the edge. We use this discrimination ability to show that dark events seen in previous detectors of a similar design are likely dominated by charge leakage along the side wall of the device. We saw only a small reduction in dark event rate with this biasing scheme, further suggesting that sidewall and edge-dominated processes are responsible for the majority of these events.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2018

Plasma exposures of a high-conductivity graphitic foam for plasma facing components

The plasma-surface interactions from samples of high-conductivity graphitic foam biased to 120 V and placed in 6–8 eV deuterium plasmas with densities as high as 10 19 m -3 were investigated at the PSI-2 linear plasma device in Jülich. Graphitic foam-plasma interactions were also studied at the Wendelstein 7-X (W7-X) stellarator in Greifswald by exposure to hydrogen and helium plasmas using the Jülich multi-purpose manipulator. The purpose was to explore the possibility of using the material in a plasma facing component, and initial results were encouraging. In W7-X, no measurable erosion or cracking was observed. The PSI-2 samples received a deuterium fluence of 5 × 10 25 m -2 resulting in an average erosion of 43 µm or about 5 mg per sample. Residual gas analysis (RGA) data were acquired to monitor sample outgassing. Laser-induced Breakdown Spectroscopy (LIBS) was used to measure deuterium retention in the porous foam. After exposure, the surfaces were characterized with scanning electron microscopy, energy dispersive x-ray analysis and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The graphitic foam has a thermal conductivity as high as 287 W/mK and is considered as a replacement to more exotic carbon fiber composites such as SepCarb NB31 or isotropic graphites like ATJ that are no longer produced but used in present-day tokamak experiments. Actively cooled monoblocks were made from the foam and underwent extensive materials characterization including infrared response studies at Oak Ridge National Laboratory. This material is under consideration for the proposed actively-cooled W7-X divertor scraper element.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2020

Exploration of Sn 70 Li 30 alloy as possible material for flowing liquid metal plasma facing components

As an advanced alternative to solid materials, Liquid Metals (LM) may offer more resilient and feasible Plasma Facing Components (PFCs). Particularly, regarding the unavoidable material erosion/degradation produced by particle/heat fluxes in future fusion devices where much longer duty cycles are expected. Furthermore, configurations that propose a flowing LM surface can add the advantage of a continuously fresh and clean layer facing the plasma. Although lithium is the most widely tested option, tin-lithium (SnLi) alloys have been proposed to attempt to combine the positive characteristics of both pure elements and ameliorate the specific issues of lithium. In this work, the potential use of Sn70Li30 alloy in such flowing concepts has been explored by addressing several preliminary and mandatory aspects for its utilization. Key issues such as wettability and compatibility of the alloy with relevant substrates have been studied in a multidisciplinary approach. The data obtained from deposited liquid tin-lithium droplets indicates approximate wetting temperatures of 360 °C, 390 °C and 405 °C for the fresh alloy on 316 stainless steel, molybdenum, and tungsten, respectively. However, the alloy contamination appeared to strongly affect the wetting characteristics of materials, increasing their wetting temperature by ~130 °C in the worst observed cases. Interestingly, in some instances, the instability of the liquid alloy surface was observed in the form of sudden gaseous ejection. The deposited droplets were posteriorly characterized in terms of absolute composition and depth profile by Inductively Coupled PlasmaOptical Emission Spectroscopy (ICP-OES) and Secondary Ion Mass Spectrometry (SIMS-ToF). Additionally, the nature and composition of the boundaries between the substrates and alloy microparticles was investigated by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and 3D Laser microscopy. The overall results of this post-mortem characterization revealed that first signs of corrosion induced by both alloy elements (lithium-chromium association and iron-tin intermetallic mixing) were present on 316 stainless steel after short exposures (≤3 h) at temperatures lower than 550 °C. Conversely, molybdenum and tungsten showed good compatibility with the alloy in equivalent conditions. The global implications of these results are finally addressed, focusing on the future perspectives and the more viable scenarios for the eventual utilization of these alloys in flowing liquid metal configurations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2026

Testing of spark plasma sintered porous tungsten under neon glow discharge cleaning conditions in LTX-β

This paper demonstrates that tungsten (W) based powder reconstituted Plasma Facing Components (PFCs) can be treated in situ in a fusion reactor to remove W oxide and carbon (C) contamination. Doing so should ease the challenge of using these materials in a Capillary Porous System (CPS) with lithium (Li) by enabling better wetting and less contamination of the Li by the underlying CPS. Most powder reconstituted materials including 3D printed and sintered PFCs suffer from a high surface contamination from oxides and surface C, which complicates their use with liquid Li, a primary PFC candidate. Spark plasma sintered porous W samples were fabricated to be used as a CPS with liquid Li. The samples were characterized in terms of morphology and surface chemistry. Analysis confirms a high C and oxygen (O) contamination. We present the results of exposing this type of CPS to Glow Discharge Cleaning (GDC) cycles in the Lithium Tokamak Experiment-β (LTX-β). The sample was exposed to neon (Ne) GDC in the midplane of the low-field side of LTX-β and analyzed in vacuo with Temperature Programmed Desorption (TPD) and Secondary Ion Mass Spectrometry (SIMS) to investigate the effects the Ne GDC had on the chemical composition of the sample. The combination of Ne GDC with rapid heating as done in TPD was successful in reducing the W oxides and removing the C contamination.

Capillary porous system↗

DOE OSTI2025

Natural top quark condensation (a redux)

The Nambu--Jona-Lasinio (NJL) model involves a pointlike 4-fermion interaction. While it gives a useful description of chiral dynamics (mainly in QCD), it nonetheless omits the crucially important internal wave-function of a two-body bound state, $\phi(r)$. This becomes significant near critical coupling where $\phi(r)$ extends to large distance, leading to dilution and suppression of induced couplings $\propto \phi(0)$, such as the Yukawa and quartic couplings, as well as reduced fine-tuning of a hierarchy. In top quark condensation, where the BEH boson is a $\bar{t}t$ bound state and we have a UV completion such as topcolor, we must go beyond the NJL model and include effects of $\phi(r)$. We provide a formulation of this for the Brout-Englert-Higgs boson, and find that it leads to an extended $\phi(r)$, a significantly reduced and natural composite scale of $M_0 \sim 6$ TeV, a successful prediction for the quartic coupling, $\lambda$, and fine tuning that is reduced to a few percent, providing a compelling candidate solution to the naturalness problem of the BEH boson. The theory is testable and new physics should begin to emerge on the multi-TeV mass scales and possibly accessible to the LHC.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Assessing the fidelity of marine vertebrate microfossil δ18O signatures and their potential for palaeo-ecological and -climatic reconstructions

Conodont biogenic apatite has become a preferred analytical target for oxygen isotope studies investigating ocean temperature and palaeoclimate change in the Palaeozoic. Despite the growing application in geochemical based palaeoenvironmental reconstructions, the paucity or absence of conodont fossils in certain facies necessitates greater flexibility in selection of robust oxygen bearing compounds for analysis. Microvertebrates offer a potential substitute for conodonts from the middle Palaeozoic. Microvertebrate bioapatite is particularly advantageous given a fossil record extending to the present with representatives across freshwater to fully marine environments, thus widening the scope of oxygen isotope studies on bioapatite. However, significant tissue heterogeneity within vertebrates and differential susceptibility of these tissues to diagenetic alteration have been raised as potential problems affecting the reliability of the oxygen isotope ratios as palaeoclimate proxies. Pristine microvertebrate and co-occurring conodont fossils from the Late Devonian and Early Carboniferous of the Lennard Shelf, Canning Basin, Western Australia, were analysed using bulk (gas isotope ratio mass spectrometry) and in-situ (secondary ion mass spectrometry) methodologies, with the latter technique allowing investigation of specific tissues within vertebrate elements. The δ18Oconodont results may be interpreted in terms of palaeolatitudinally and environmentally sensible palaeotemperatures and provide a baseline standard for comparison against δ18Omicrovertebrate values. Despite an absence of obvious diagenetic influences, GIRMS of microvertebrate denticles yielded δ18O values depleted by 2-4 ‰ relative to co-occurring conodonts. SIMS analysis of hypermineralised tissues in both scales and teeth produced δ18O values comparable with those of associated conodonts. The susceptibility of porous phosphatic fossil tissues to microbial activity, fluid interaction and introduction of mineral precipitates post-formation is demonstrated in microvertebrate dentine, which showed significant heterogeneity and consistent depletion in 18O. The hypermineralised tissues present in both teeth and scales appear resistant to many diagenetic processes and indicate potential for palaeoclimatic reconstructions and palaeoecological investigations.

conodont↗

DOE OSTI2022

Hydrodynamics and Load Shedding Behavior of a Variable-Geometry Oscillating Surge Wave Energy Converter (OSWEC)

In order to improve their long-term viability, wave energy converters (WECs) need to be able to shed loads when a threshold wave condition is exceeded. As shown by Tom et al. (2016) [1], provision of adjustable flaps within the body of an oscillating surge wave energy converter (OSWEC) allows wave energy to pass through the device. A control system may then be able to open and close the flaps when waves approaching the device exceed preset thresholds. The variable-geometry OSWEC (VG-OSWEC) concept studied in this paper is a bottom-hinged, rectangular wave paddle with five flaps of elliptical cross-section embedded into the face of the paddle. System ID tests were conducted on this VG-OSWEC device at a 1:14 scale in a wave basin. Free decay tests showed that the damping was distinctly nonlinear when the flaps were fully open, and the natural frequency increased by 40% when compared with the flaps in a fully closed configuration. Tests with regular wave conditions were used to develop the response amplitude operator for the rotational motion about the hinge. These response amplitude operator results when compared with numerical simulations run using WEC-Sim/WAMIT and ANSYS AQWA, show strong agreement with the flap open and closed conditions. The regular-wave condition measurements also show that the wave excitation moment about the hinge was reduced by up to 60% when the flaps were fully open. The experiments serve to demonstrate the potential of the variable geometry design to shed loads and survive harsh ocean environments.

load shedding↗

DOE OSTI2025

On the optimal sizing of power take-off systems for wave energy converters

The power take-off (PTO) system in a wave energy converter (WEC) is the means by which the energy in an ocean wave is converted into useful energy. There has been a general lack of technology convergence in the wave energy industry and PTO design has been largely device-specific with the design process determined by the WEC developer. An optimized PTO design can significantly affect the efficiency, reliability, performance, and overall cost and viability of a device. There remains a need in the marine energy industry for best practices and efficient design processes to be identified as it could greatly benefit developers and researchers in designing an optimal WEC PTO. This research utilizes the open-source Matlab-Simulink based software, WEC-Sim, which was developed by the National Renewable Energy Laboratory, and the Eagle, a high-performance computing system, to model and optimize two WECs of different archetypes and then investigates if any trends exist that can be exploited for greater efficiency in optimal PTO design. The results from this research indicate that there may be an optimal sizing for WEC PTOs for both power and PTO force rating and that substantial reductions can be made in the cost of a device without significant loss in the energy produced. Furthermore this optimal sizing may be independent of WEC type and deployment location. With an optimal, or near optimal, approach to WEC PTO sizing demonstrated, a methodology is proposed to address the challenge of nameplate ratings in the wave energy industry.

13 HYDRO ENERGY↗