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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Boosting Thermoelectric Performance in Nanocrystalline Ternary Skutterudite Thin Films through Metallic CoTe 2 Integration

Metal–semiconductor nanocomposites have emerged as a viable strategy for concurrently tailoring both thermal and electronic transport properties of established thermoelectric materials, ultimately achieving synergistic performance. In this investigation, a series of nanocomposite thin films were synthesized, embedding metallic cobalt telluride (CoTe 2 ) nanophase within the nanocrystalline ternary skutterudite (Co(Ge 1.22 Sb 0.22 )Te 1.58 or CGST) matrix. Our approach harnessed composition fluctuation-induced phase separation and in situ growth during thermal annealing to seamlessly integrate the metallic phase. The distinctive band structures of both materials have developed an ohmic-type contact characteristic at the interface, which raised carrier density considerably yet negligibly affected the mobility counterpart, leading to a substantial improvement in electrical conductivity. The intricate balance in transport properties is further influenced by the metallic CoTe 2 phase’s role in diminishing lattice thermal conductivity. The presence of the metallic phase instigates enhanced phonon scattering at the interface boundaries. Consequently, a 2-fold enhancement in the thermoelectric figure of merit (zT ~ 1.30) is attained with CGST-7 wt. % CoTe 2 nanocomposite film at 655 K compared to that of pristine CGST.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta(CoTe)2 by Materials Project

Ta(CoTe)2 crystallizes in the orthorhombic Pnma space group. The structure is two-dimensional and consists of two Ta(CoTe)2 sheets oriented in the (0, 0, 1) direction. there are two inequivalent Ta sites. In the first Ta site, Ta is bonded in a 10-coordinate geometry to eight Co and two equivalent Te atoms. There are four shorter (2.56 Å) and four longer (2.84 Å) Ta–Co bond lengths. Both Ta–Te bond lengths are 2.87 Å. In the second Ta site, Ta is bonded in a 11-coordinate geometry to eight Co and three Te atoms. There are four shorter (2.64 Å) and four longer (2.71 Å) Ta–Co bond lengths. There are one shorter (2.82 Å) and two longer (3.02 Å) Ta–Te bond lengths. There are four inequivalent Co sites. In the first Co site, Co is bonded in a 10-coordinate geometry to four Ta, three Co, and three Te atoms. There are a spread of Co–Co bond distances ranging from 2.56–2.86 Å. There are a spread of Co–Te bond distances ranging from 2.54–2.62 Å. In the second Co site, Co is bonded in a 10-coordinate geometry to four Ta, three Co, and three Te atoms. There are one shorter (2.60 Å) and one longer (2.84 Å) Co–Co bond lengths. There are a spread of Co–Te bond distances ranging from 2.54–2.62 Å. In the third Co site, Co is bonded in a 10-coordinate geometry to four Ta, three Co, and three Te atoms. There are one shorter (2.56 Å) and one longer (2.60 Å) Co–Co bond lengths. There are a spread of Co–Te bond distances ranging from 2.54–2.62 Å. In the fourth Co site, Co is bonded in a 10-coordinate geometry to four Ta, three Co, and three Te atoms. There are one shorter (2.64 Å) and one longer (2.71 Å) Co–Ta bond lengths. The Co–Co bond length is 2.86 Å. There are a spread of Co–Te bond distances ranging from 2.54–2.62 Å. There are three inequivalent Te sites. In the first Te site, Te is bonded in a 5-coordinate geometry to one Ta and four Co atoms. In the second Te site, Te is bonded in a 6-coordinate geometry to two Ta, two Co, and two equivalent Te atoms. There are one shorter (3.25 Å) and one longer (3.33 Å) Te–Te bond lengths. In the third Te site, Te is bonded in a 4-coordinate geometry to four Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoTe by Materials Project

CoTe is Tungsten Carbide-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Co2+ is bonded to six equivalent Te2- atoms to form a mixture of edge, corner, and face-sharing CoTe6 octahedra. The corner-sharing octahedral tilt angles are 51°. All Co–Te bond lengths are 2.62 Å. Te2- is bonded in a 6-coordinate geometry to six equivalent Co2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y5(CoTe)2 by Materials Project

Y5(CoTe)2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are three inequivalent Y sites. In the first Y site, Y is bonded in a 7-coordinate geometry to three Co and four equivalent Te atoms. There are one shorter (2.83 Å) and two longer (2.84 Å) Y–Co bond lengths. There are two shorter (3.33 Å) and two longer (3.35 Å) Y–Te bond lengths. In the second Y site, Y is bonded in a 6-coordinate geometry to three Co and three equivalent Te atoms. There are two shorter (2.85 Å) and one longer (2.92 Å) Y–Co bond lengths. There are one shorter (3.15 Å) and two longer (3.20 Å) Y–Te bond lengths. In the third Y site, Y is bonded in a distorted square co-planar geometry to two Co and two equivalent Te atoms. There are one shorter (2.95 Å) and one longer (3.26 Å) Y–Co bond lengths. Both Y–Te bond lengths are 3.18 Å. There are two inequivalent Co sites. In the first Co site, Co is bonded in a 9-coordinate geometry to seven Y and two equivalent Co atoms. Both Co–Co bond lengths are 2.38 Å. In the second Co site, Co is bonded in a 9-coordinate geometry to seven Y and two equivalent Co atoms. Te is bonded in a 8-coordinate geometry to eight Y atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

CoTe 2 : A Quantum Critical Dirac Metal with Strong Spin Fluctuations

Abstract Quantum critical points separating weak ferromagnetic and paramagnetic phases trigger many novel phenomena. Dynamical spin fluctuations not only suppress the long‐range order, but can also lead to unusual transport and even superconductivity. Combining quantum criticality with topological electronic properties presents a rare and unique opportunity. Here, by means of ab initio calculations and magnetic, thermal, and transport measurements, it is shown that the orthorhombic CoTe 2 is close to ferromagnetism, which appears suppressed by spin fluctuations. Calculations and transport measurements reveal nodal Dirac lines, making it a rare combination of proximity to quantum criticality and Dirac topology.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er5(CoTe)2 by Materials Project

Er5Co2Te2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are three inequivalent Er sites. In the first Er site, Er is bonded in a distorted square co-planar geometry to two Co and two equivalent Te atoms. There are one shorter (2.90 Å) and one longer (3.18 Å) Er–Co bond lengths. Both Er–Te bond lengths are 3.17 Å. In the second Er site, Er is bonded in a 6-coordinate geometry to three Co and three equivalent Te atoms. There are two shorter (2.79 Å) and one longer (2.90 Å) Er–Co bond lengths. There are one shorter (3.13 Å) and two longer (3.19 Å) Er–Te bond lengths. In the third Er site, Er is bonded in a 7-coordinate geometry to three Co and four equivalent Te atoms. There are two shorter (2.79 Å) and one longer (2.81 Å) Er–Co bond lengths. There are two shorter (3.32 Å) and two longer (3.36 Å) Er–Te bond lengths. There are two inequivalent Co sites. In the first Co site, Co is bonded in a 9-coordinate geometry to seven Er and two equivalent Co atoms. Both Co–Co bond lengths are 2.40 Å. In the second Co site, Co is bonded in a 9-coordinate geometry to seven Er and two equivalent Co atoms. Te is bonded in a 8-coordinate geometry to eight Er atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoTe(PbO3)2 by Materials Project

Pb2CoTeO6 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Co4+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six equivalent TeO6 octahedra. The corner-sharing octahedra tilt angles range from 14–18°. There are four shorter (2.13 Å) and two longer (2.14 Å) Co–O bond lengths. Pb2+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of Pb–O bond distances ranging from 2.61–3.16 Å. Te4+ is bonded to six O2- atoms to form TeO6 octahedra that share corners with six equivalent CoO6 octahedra. The corner-sharing octahedra tilt angles range from 14–18°. There is two shorter (1.95 Å) and four longer (1.96 Å) Te–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Co4+, four equivalent Pb2+, and one Te4+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Co4+, four equivalent Pb2+, and one Te4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoTe(PbO3)2 by Materials Project

Pb2CoTeO6 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Co4+ is bonded to six equivalent O2- atoms to form CoO6 octahedra that share corners with six equivalent TeO6 octahedra. The corner-sharing octahedral tilt angles are 17°. All Co–O bond lengths are 2.14 Å. Pb2+ is bonded in a 12-coordinate geometry to nine equivalent O2- atoms. There are a spread of Pb–O bond distances ranging from 2.58–2.93 Å. Te4+ is bonded to six equivalent O2- atoms to form TeO6 octahedra that share corners with six equivalent CoO6 octahedra. The corner-sharing octahedral tilt angles are 17°. All Te–O bond lengths are 1.96 Å. O2- is bonded in a 2-coordinate geometry to one Co4+, three equivalent Pb2+, and one Te4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoTe(PbO3)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2025

Energizing Robust Sulfur/Lithium Electrochemistry via Nanoscale-Asymmetric-Size Synergism

Sluggish redox kinetics and dendrite growth perplex the fulfillment of efficient electrochemistry in lithium–sulfur (Li–S) batteries. The complicated sulfur phase transformation and sulfur/lithium diversity kinetics necessitate an all-inclusive approach in catalyst design. Herein, a compatible mediator with nanoscale-asymmetric-size configuration by integrating Co single atoms and defective CoTe 2–x (Co SA -CoTe 2–x @NHCF) is elaborately developed for regulating sulfur/lithium electrochemistry synchronously. Substantial electrochemistry and theoretical analyses reveal that CoTe 2–x exhibits higher catalytic activity in long-chain polysulfide transformation and Li 2 S decomposition, while monodispersed Co sites are more effective in boosting sulfur reduction kinetics to regulate Li 2 S deposition. Such cascade catalysis endows Co SA -CoTe 2–x @NHCF with the all-around service of “trapping-conversion-recuperation” for sulfur species during the whole redox reaction. Furthermore, it is demonstrated by in situ transmission electron microscopy that initially formed electronic-conductive Co and ionic-conductive Li 2 Te provide sufficient lithiophilic sites to regulate homogeneous Li plating and stripping with markedly suppressed dendrite growth. Consequently, by coupling the Co SA -CoTe 2–x @NHCF interlayer and Li@Co SA -CoTe 2–x @NHCF anode, the constructed Li–S full batteries deliver superior cycling stability and rate performance, and the flexible pouch cell exhibits stable cycling performance at 0.3 C. In conclusion, the gained insights into the synergistic effect of asymmetric-size structures pave the way for the integrated catalyst design in advanced Li–S systems.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Large off-diagonal magnetoelectricity in a triangular Co2+-based collinear antiferromagnet

Abstract Magnetic toroidicity is an uncommon type of magnetic structure in solid-state materials. Here, we experimentally demonstrate that collinear spins in a material with R -3 lattice symmetry can host a significant magnetic toroidicity, even parallel to the ordered spins. Taking advantage of a single crystal sample of CoTe 6 O 13 with an R -3 space group and a Co 2+ triangular sublattice, temperature-dependent magnetic, thermodynamic, and neutron diffraction results reveal A-type antiferromagnetic order below 19.5 K, with magnetic point group -3′ and k = (0,0,0). Our symmetry analysis suggests that the missing mirror symmetry in the lattice could lead to the local spin canting for a toroidal moment along the c axis. Experimentally, we observe a large off-diagonal magnetoelectric coefficient of 41.2 ps/m that evidences the magnetic toroidicity. In addition, the paramagnetic state exhibits a large effective moment per Co 2+ , indicating that the magnetic moment in CoTe 6 O 13 has a significant orbital contribution. CoTe 6 O 13 embodies an excellent opportunity for the study of next-generation functional magnetoelectric materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2006

Satellite Detection of Ebola River Hemorrhagic Fever Epidemics Trigger Events

Ebola hemorrhagic fever, named after the Ebola River in Central Africa, first appeared in June 1976, during an outbreak in Nzara and Maridi, Sudan. In September 1976, a separate outbreak was recognized in Yambuku, Democratic Republic of the Congo (DRC). One fatal case was identified in Tandala, DRC, in June 1977, followed by another outbreak in Nzara, Sudan, in July 1979. Ebola hemorrhagic fever outbreaks results in a very high mortality of patients who contract the disease: from 50 to 80% of infected people perish from this highly virulent disease. Death is gruesome, with those afflicted bleeding to death from massive hemorrhaging of organs and capillaries. The disease was not identified again until the end of 1994, when three outbreaks occurred almost simultaneously in Africa. In October, an outbreak was identified in a chimpanzee community studied by primatologists in Tal, Cote d'lvoire, with one human infection. The following month, multiple cases were reported in northeast Gabon in the gold panning camps of Mekouka, Andock, and Minkebe. Later that same month, the putative index case of the 1995 Kikwit, DRC, outbreak was exposed through an unknown mechanism while working in a charcoal pit. In Gabon, two additional outbreaks were reported in February and JuIy,1996, respectively, in Mayibout II, a village 40 km south of the original outbreak in the gold panning camps, and a logging camp between Ovan and Koumameyong, near Booue. The largest Ebola hemorrhagic fever epidemic occurred in Gulu District, Uganda from August 2000 to January 2001. In December 2001, Ebola reappeared in the Ogooue-lvindo Province, Gabon with extension into Mbomo District, The Republic of the Congo lasting until July 2002. Since 2002 there have been several outbreaks of Ebola hemorrhagic fever in Gabon and adjacent areas of Congo. Of interest is the seasonal context and occasional temporal clustering of Ebola hemorrhagic fever outbreaks. Near simultaneous appearances of Ebola epidemics in Nzara, Sudan and Yambuku, DRC in 1976 occurred within two months of each other in two geographic locations separated by hundreds of kilometers involving two separate viral strains (Sudan and Zaire EBO strains). The outbreaks of Tal, Cote d'lvoire; Mekouka, Gabon; and Kikwit, DRC in late 1994 also occurred within months of each other in three different geographic regions involving two different viral strains (Cote d'lvoire and Zaire EBO strains). Fifteen years passed between the 1976-9 and 1994-6 temporal clusters of Ebola cases without identification of additional cases.

Tucker, Compton J.↗
NASA NTRS2015

Anti-Adhesion Elastomer Seal Coatings for Ultraviolet and Atomic Oxygen Protection

Radiation blocking sunscreen coatings have been developed for the protection of elastomer seals used in low-Earth-orbit (LEO). The coatings protect the seals from ultraviolet (UV) radiation and atomic oxygen (AO) damage. The coatings were developed for use on NASA docking seals. Docking seal damage from the UV and AO present in LEO can constrain mission time-line, flight mode options, and increases risk. A low level of adhesion is also required for docking seals so undocking push-off forces can be low. The coatings presented also mitigate this unwanted adhesion. Greases with low collected volatile condensable materials (CVCM) and low total mass loss (TML) were mixed with slippery and/or UV blocking powders to create the protective coatings. Coatings were applied at rates up to 2 milligrams per square centimeter. Coated seals were exposed to AO and UV in the NUV (near-UV) and UV-C wavelength ranges (300 to 400 nanometers and 254 nanometers, respectively). Ground based ashers were used to simulate the AO of space. The Sun's UV energy was mimicked assuming a nose forward flight mode, resulting in an exposure rate of 2.5 megajoules per square meter per day. Exposures between 0 and 147 megajoules per square meter (UV-C) and 245 megajoules per square meter (NUV) were accomplished. The protective coatings were durable, providing protection from UV after a simulated docking and undocking cycle. The level of protection begins to decline at coverage rates less than 0.9 milligrams per square centimeter. The leakage of seals coated with Braycote plus 20 percent Z-cote ZnO sunscreen increased by a factor of 40 after moderate AO exposure; indicating that this coating might not be suitable due to AO intolerance. Seals coated with DC-7-16.4 percent Z-cote ZnO sunscreen were not significantly affected by combined doses of 2 x 10 (sup 21) atoms per square AO with 73 megajoules per square meter UV-C. Unprotected seals were significantly damaged at UV-C exposures of 0.3 megajoules per square meter and DC-7-16.4 percent Z-cote coated seals were undamaged at all exposures up to the limits tested thus far which were 147 megajoules per square meter UV-C and 245 megajoules per square meter NUV. The coatings decreased adhesion sufficiently for docking seals at temperatures equal to or greater than -8 degrees Centigrade thus offer a simple and inexpensive way to mitigate adhesion.

adhesion↗
DOE OSTI2020

Mind the Gap: Building Simulation in the Architectural Design Studio

Building modelling and simulation approaches are increasingly being utilized in architectural design studios to guide and inform the design process and offer evidence-based feedback on proposed building performance. The development of intuitive and simplified simulation interfaces has greatly contributed to achieving this integration. One aspect that is often overlooked is the workflow that governs and regulates integrated design, which can have significant impacts on final design outcomes. Currently there are numerous software packages available for building performance simulations. This makes it challenging to select an appropriate tool that provides accurate results yet allows a designer to make informed architectural decisions with a designer-friendly interface. Furthermore, workflows to incorporate simulations into the design process proved to highly impact student’s project design integration. Yet, it is not clear what type of workflows are successful to achieve this goal, under what conditions, and/or for which building and site typologies. This paper addresses these issues by first reviewing three different workflows for integrating building performance simulation processes and highlighting their strengths and weaknesses. Second, a comparative case study approach was employed to test three of the most common workflows in three different integrated design architectural studios at the senior and vertical studio levels as well as in two courses that run parallel and complementary to the design studios. The workflows, processes, and the resultant student projects were further analyzed based on criteria for better integrated design and architectural excellence as outlined in the American Institute of Architects Committee on the Environment (AIA COTE) Top 10 Student’s Competition. Third, to situate the pedagogical case studies’ results within a larger context, a survey of the AIA COTE Top 10 student competition award recipients over the last five years was conducted. The results are summarized in a pedagogical framework that outlines best strategies of the type of workflows, software, design process used, methods to achieve desired interaction between design process and analytical feedback, and metrics for educators to evaluate the success of this integration and their learning outcomes in the design studio. The goal is to help bridge the gap between the building design and simulation within the design studio’s creative process for more integrated design outcomes.

Elzeyadi, Ihab↗
DOE OSTI2025

Significance of the structural configuration of B2 disorder in Co and Ti based Heusler alloys

We investigate here structural (at local and global levels) and transport properties for 𝑋 2 ⁢MnAl (𝑋= Co and Ti). Additionally, the magnetic properties were also studied for Ti 2 ⁢MnAl. Our x-ray diffraction results show that both the compounds stabilize in B2 disordered phase with cubic structure of 𝑃⁢𝑚⁢$\overline{3}$⁢𝑚 space group. Further, the structural configuration of the above disordered phase for both the compounds was identified using combined studies of x-ray absorption spectroscopy and multiple scattering calculations at the transition metal 𝐾 edges. Upon such identification, in the case of Co 2 ⁢Mn 1−𝑦⁢ Cr 𝑦 ⁢Al (𝑦= 0, 0.05, 0.1, 0.2) with change in 𝑦, we are able to establish a better connection quantitatively between the inverse of Mn-Co bonds and peak in the temperature-dependent resistivity. This highlights the crucial importance of a detailed understanding of the nature of B2 disorder. In the case of 𝑦=0, in the temperature range of study, the resistivity is driven by the functional form associated with (a) three-dimensional enhanced electron-electron Coulomb interaction scattering mechanism and (b) an unconventional one-magnon process. For Ti 2 ⁢MnAl, the transport shows metallic glasslike behavior at high temperature, while at low temperature it follows both the Cote-Meisel's model and quantum correction model. In this compound, the magnetic studies suggest the formation of superparamagnetic clusters in the paramagnetic matrix at low temperatures. Our density functional theory results are in line with the transport and magnetic properties. In literature, the spin polarization percentage (𝑃) for 𝑋= Co in B2 disordered phase is 76%. However, the present results emphasize the fact that in B2 disordered phase, the value of 𝑃 can range from 90% to 71% depending on the structural configuration introduced by swapping of the atomic positions of Mn and Al. For the compound under study, the value of percentage spin polarization obtained ranges between 82% to 85%. In addition, we also identify the origin of the difference in the shape of the Mn 3⁢𝑑 density of states for both the alloys. In conclusion, our results for 𝑋= Co alloy highlights the importance of identifying the specific structural configuration associated with a particular disorder category especially in the estimation of 𝑇 𝑐 and 𝑃 and for 𝑋= Ti, the physical properties can be tuned by varying the position of 𝐸 𝐹 and thereby its utilization in device applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

From print to digital: Preserving over 10,000 McKibbin Cards

Collections management staff from the National Security Research Center (NSRC) recently digitized more than 10,000 McKibbin Cards to make them accessible on the Lab’s unclassified network, said NSRC collections management team leader Patricia Cote (WRS-NSRCMS). The cards, named after Dorothy McKibbin, who was known as the gatekeeper of Los Alamos because she was often the first point of contact for new hires, have become symbolic of the Lab when the world’s greatest minds secretly gathered to create the first atomic bomb and end World War II.

96 KNOWLEDGE MANAGEMENT AND PRESERVATION↗