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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Poly(methyl methacrylate)/layered zinc sulfide nanocomposites: Preparation, characterization and the improvements in thermal stability, flame retardant and optical properties

Highlights: • Layered zinc sulfide (LZnS) was synthesized successfully via hydrothermal method. • We prepare PMMA/LZnS nanocomposites by in situ bulk polymerization of MMA. • PMMA/LZnS nanocomposites were investigated by TGA, DSC, MCC, UV–vis and PL test. • The thermal stability, flame retardant and optical properties of PMMA are improved. - Abstract: Layered zinc sulfide (LZnS) was synthesized successfully via hydrothermal method and poly(methyl methacrylate) (PMMA)/layered zinc sulfide nanocomposites were obtained by in situ bulk polymerization of methyl methacrylate (MMA). X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the as-synthesized layered zinc sulfide and PMMA/layered zinc sulfide nanocomposites. Microscale combustion calorimeter (MCC), differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA) were used to test the thermal properties of the composites. Ultraviolet visible (UV–vis) transmittance spectra and photoluminence (PL) spectra were obtained to investigate the optical properties of the composites. From the results, the thermal degradation temperature is increased by 20–50 °C, the peak of heat release rate (pHRR) and total heat release (THR) are both decreased by above 30%, and the photoluminence intensity is enhanced with the increasing loading of layered zinc sulfide.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Morphology-controlled synthesis of Co{sub 3}O{sub 4} by one step template-free hydrothermal method

Highlights: • Co{sub 3}O{sub 4} crystals had been synthesized by one step template-free hydrothermal method. • The H{sub 2}O{sub 2} plays a crucial role in morphological control of Co{sub 3}O{sub 4} nanostructures. • The morphology has significant effect on the optical property of Co{sub 3}O{sub 4}. - Abstract: We had developed a facile synthetic route of Co{sub 3}O{sub 4} crystals with different morphologies via one step template-free hydrothermal method. The phase and composition of the Co{sub 3}O{sub 4} were investigated by X-ray powder diffraction and Raman spectrum. The morphology and structure of the synthesized samples were characterized by scanning electron microscopy and transmission electron microscopy. The H{sub 2}O{sub 2} played a crucial role in morphological control of Co{sub 3}O{sub 4} nanostructures. It only obtained Co-based precursor in the absence of H{sub 2}O{sub 2}. On the contrary, the Co{sub 3}O{sub 4} with different morphologies including nanoparticles, nano-discs and well-defined octahedral nanostructures were synthesized in the presence of H{sub 2}O{sub 2}. In addition, the optical property of the obtained Co{sub 3}O{sub 4} samples was investigated by UV–vis spectra.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

The GdF3 phosphors with enhanced multicolor luminescence via multi-channel excitation and energy migration procedure

Highlights: • Core-shell structured GdF{sub 3} phosphors were synthesized by hydrothermal method. • SiO{sub 2} coating layers prevent aggregation and sintering during thermal annealing. • The annealed CSS nanophosphors were highly dispersible. • The inserted PMA significantly enhances multicolor luminescence. • The annealed CSS phosphors exhibit enhanced multicolor luminescence properties. - Abstract: A collection of GdF{sub 3} core-shell structured (CSS) phosphors were synthesized by hydrothermal method. The as-prepared (AP) phosphors were coated with SiO{sub 2} layers to avoid aggregation and sintering during thermal annealing at 800 °C, after which the SiO{sub 2} layers were etched off and the annealed phosphors became highly dispersible. The annealed CSS phosphor aGdF{sub 3}:Eu{sup 3+}@GdF{sub 3}:Ce{sup 3+},Dy{sup 3+} shows excellent multicolor luminescence performance with the aid of dual-channel excitation and energy migration (EM) procedure of Gd{sup 3+} ions. By inserting pyromellitic acid (PMA) organic ligands into the interfaces between annealed core and AP shell layer regions, the so-called antenna effect of organic ligands of PMA forms a new excitation channel, which makes the CSS phosphor aGdF{sub 3}:Eu{sup 3+}@PMA@GdF{sub 3}:Ce{sup 3+},Dy{sup 3+} exhibit significantly enhanced multicolor luminescence via multi-channel excitation and EM process. The prepared CSS phosphors in this work are excellent candidates for applications in solid-state lighting.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Sintering behaviors, phases, and dielectric properties of MO-TeO2-V2O5 (M = Ca, Sr, Ba) ultralow temperature ceramics

Highlights: • Introduction of TeO{sub 2} to MO-V{sub 2}O{sub 5} (M = Ca,Sr,Ba) ceramics promoted a M{sub 2}V{sub 2}O{sub 7} phase formation, and obtain excellent dielectric properties and a densification sintering at below 600°. • Chemical compatibility of ULTCC ceramics with aluminum electrode indicated that aluminum did not react with MO-TeO{sub 2}-V{sub 2}O{sub 5} ceramics. • Aluminum easily encouraged the transformation of M{sub 2}V{sub 2}O{sub 7} structures to M{sub 3}(VO{sub 4}){sub 2} structures and other structures under the ultra-low temperature sintering. - Abstract: Influences of TeO{sub 2} on phase evolutions and sintering behaviors of MO-TeO{sub 2}-V{sub 2}O{sub 5} (M = Ca, Sr, Ba) ultralow temperature ceramics were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Dielectric properties of MO-TeO{sub 2}-V{sub 2}O{sub 5} (M = Ca, Sr, Ba) ceramics and their chemical compatibility with an aluminum electrode were also studied. Introducing TeO{sub 2} to MO-V{sub 2}O{sub 5} (M = Ca, Sr, Ba) ceramics obviously decreased the sintering temperature and promoted formation of M{sub 2}V{sub 2}O{sub 7} (M = Ca, Sr, Ba) phases. Also, dielectric properties mainly depend on the amount of TeO{sub 2} added to MO-TeO{sub 2}-V{sub 2}O{sub 5} ceramics. Investigation of chemical compatibility with aluminum shows that aluminum does not react chemically with MO-TeO{sub 2}-V{sub 2}O{sub 5} ceramics; however, aluminum causes transformation of M{sub 2}V{sub 2}O{sub 7} phases to other phases (such as M{sub 3}(VO{sub 4}){sub 2}) to be easier. Sintering temperature of MO-TeO{sub 2}-V{sub 2}O{sub 5} (M = Ca, Sr, Ba) ceramics can be regulated below 600 °C, which is much less than the melting point of aluminum. In addition, MO-TeO{sub 2}-V{sub 2}O{sub 5} (M = Ca, Ba) ceramics maintain quality factors of ∼18,000 GHZ, a dielectric constant of 10–12, and dielectric loss lower than 10{sup −4}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Hierarchically MoS2 nanospheres assembled from nanosheets for superior CO gas-sensing properties

Highlights: • Preparation of 3D Hierarchical large surface area MoS{sub 2} nanospheres from nansheets. • The efficient enhanced gas-sensing response of 92.6 at 500 ppm for CO at 230 °C. • Higher selectivity towards CO than other gases at different temperature ranges. - Abstract: Hierarchical three dimensional MoS{sub 2}nanostructures composed of small sheet-like nanostructures are successfully prepared using a simple two-step hydrothermal process with sodium dodecyl sulfate (SDS), as a surface modifier. The as-preparedMoS{sub 2}nanospheres are characterized by XRD, BET, XPS, EDS, SEM and HRTEM. The gas–sensing properties of as–prepared MoS{sub 2}nanostructures are tested at 175–230 °C temperatures for 50–500 ppm concentration range, using an efficient ceramic-tube sensor system via an intelligent gas testing system. A high response and selectivity towards carbon monoxide than other gases is observed. Comparative studies of MoS{sub 2}nanostructures for different concentration of carbon monoxide gas and definite sensor-stability for different gases are studied, as well. The sensor fabrication and sensing mechanism is discussed as well.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Enhanced photocatalytic degradation of phenol over Ag3PO4-BiOCl1−xBrx composites

Highlights: • Ag{sub 3}PO{sub 4}-BiOCl{sub 1−x}Br{sub x} composites were successfully synthesized and characterized. • The band energy of composites can be tunable by solid-solution strategy. • Appropriate band-gap structure facilitates charge separation property and light absorption. - Abstract: In this paper, a series of Ag{sub 3}PO{sub 4}-BiOCl{sub 1−x}Br{sub x} composites with adjustable band gap has been fabricated by using a facile two-step synthetic method. The photocatalytic activity of Ag{sub 3}PO{sub 4}-BiOCl{sub 1−x}Br{sub x} was evaluated by photocatalytic decomposition of phenol aqueous solution under simulated solar light irradiation. The result shows that Ag{sub 3}PO{sub 4}-BiOCl{sub 0.75}Br{sub 0.25} (1:5) composite possesses the best photocatalytic activity among all the as-prepared samples. The photocatalytic activity of Ag{sub 3}PO{sub 4}-BiOCl can be enhanced mainly owing to the strong light absorption ability by loading Ag{sub 3}PO{sub 4} on the surface of BiOCl, while the photocatalytic activities of Ag{sub 3}PO{sub 4}-BiOCl{sub 1−x}Br{sub x} (x = 0.25, 0.5, 0.75 and 1) composites could be enhanced by restraining the recombination of photo-generated electron-hole pairs. The enhanced solar-light photocatalytic activities of Ag{sub 3}PO{sub 4}-BiOCl{sub 1−x}Br{sub x} composites could be ascribed to the adjustable energy band structure, which facilitates the separation of photoinduced carriers. In addition, superoxide radicals (O{sub 2}{sup −}), holes (h{sup +}) and OH are considered to dominate the photocatalytic degration process. Moreover, a possible mechanism of deep understanding on the base of experimental results was proposed.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Synthesis of carbon core–shell pore structures and their performance as supercapacitors

High-power supercapacitors require excellent electrolyte mobility within the pore network and high electrical conductivity for maximum capacitance and efficiency. Achieving high power typically requires sacrificing energy densities, as the latter demands a high specific surface area and narrow porosity that impedes ion transport. Here, we present a novel solution for this optimization problem: a nanostructured core–shell carbonaceous material that exhibits a microporous carbon core surrounded by a mesoporous, graphitic shell. The tunable synthesis parameters yielded a structure that features either a sharp or a gradual transition between the core and shell sections. Electrochemical supercapacitor testing using organic electrolyte revealed that these novel core–shell materials outperform carbons with homogeneous pore structures. The hybrid core–shell materials showed a combination of good capacitance retention, typical for the carbon present in the shell and high specific capacitance, typical for the core material. These materials achieved power densities in excess of 40 kW kg -1 at energy densities reaching 27 Wh kg -1 .

25 ENERGY STORAGE↗
DOE OSTI2017

Structure-dependent performance of TiO 2 /C as anode material for Na-ion batteries

The performance of energy storage materials is highly dependent on their nanostructures. Herein, hierarchical rod-in-tube TiO 2 with a uniform carbon coating is synthesized as the anode material for sodium-ion batteries by a facile solvothermal method. This unique structure consists of a tunable nanorod core, interstitial hollow spaces, and a functional nanotube shell assembled from two-dimensional nanosheets. By adjusting the types of solvents used and reaction time, the morphologies of TiO 2 /C composites can be tuned to nanoparticles, microrods, rod-in-tube structures, or microtubes. Among these materials, rod-in-tube TiO 2 with a uniform carbon coating shows the highest electronic conductivity, specific surface area (336.4 m 2 g -1 ), and porosity, and these factors lead to the best sodium storage capability. Benefiting from the unique structural features and improved electronic/ionic conductivity, the as-obtained rod-in-tube TiO 2 /C in coin cell tests exhibits a high discharge capacity of 277.5 and 153.9 mAh g -1 at 50 and 5000 mA g -1 , respectively, and almost 100% capacity retention over 14,000 cycles at 5000 mA g -1 . In operando high-energy X-ray diffraction further confirms the stable crystal structure of the rod-in-tube TiO 2 /C during Na + insertion/extraction. Finally, this work highlights that nanostructure design is an effective strategy to achieve advanced energy storage materials.

25 ENERGY STORAGE↗
DOE OSTI2019

Sub-5 nm edge-rich 1T'-ReSe 2 as bifunctional materials for hydrogen evolution and sodium-ion storage

The rhenium-based transition metal dichalcogenides (TMDs), as new members in the TMDs family, have raised great interests recently. Due to the anisotropic structure and unique photoelectric properties, they have potential applications for electrochemical energy conversion and storage. In this work, we performed density functional theory (DFT) calculations on pristine 1T'-ReSe 2 toward hydrogen evolution reaction (HER). The results indicated that the Gibbs free energy of the 1T'-ReSe 2 edge site for HER could be as small as 0.01 eV, superior to other reported TMDs. Experimentally, we developed a strategy to fabricate sub-5 nm sized 1T'-ReSe 2 nanoflakes on carbon nanotubes. Such a small size for the nanoflakes brought abundant edge exposure, which boosted the catalytic activity in the HER. Specifically, the 1T'-ReSe 2 nanoflakes needed only 23 and 60 mV overpotentials to achieve –1 and –10 mA cm –2 current densities, along with a low Tafel slope of 37 mV dec –1 and a high exchange current density of 0.3 mA cm –2 . The edge-rich and layered 1T'-ReSe 2 was also explored as an anode for sodium ion battery. The in operando X-ray absorption near edge structure (XANES) technique was applied to investigate the TMD behavior in real-time during the sodiation/desodiation process. Furthermore, the in situ results revealed that the nanosized 1T'-ReSe 2 is electrchemically reversible during discharge/charge cycles. The electrochemical test results demonstrated that 1T'-ReSe 2 could be a promising anode material for alkaline batteries.

25 ENERGY STORAGE↗
DOE OSTI2019

Nitrogen-coordinated single iron atom catalysts derived from metal organic frameworks for oxygen reduction reaction

Iron and nitrogen co-doped carbon (Fe-N-C) catalysts hold great promise to replace platinum group metal used for the oxygen reduction reaction (ORR) in low-temperature fuel cells. However, general synthesis routes require tedious acid washing and extensive heat treatment, usually resulting in uncontrollable morphologies and undesirable compounds. In this work, a zeolitic imidazolate framework (ZIF-8) was employed as a self-template for one-pot synthesis of a Fe-N-C catalyst consisting of uniformly dispersed Fe single atoms. Atomically dispersed Fe atoms were well distributed along the edges of the porous carbon matrix. Each of the Fe atoms was coordinated with four N atoms in the plane and two O atoms in the axial direction. The optimized Fe-N-C catalyst showed excellent ORR activities with half-wave potentials of 0.81 and 0.90 V in acidic and alkaline solutions, respectively. The results may be important for the optimization of single-atom-based catalysts for various reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

1T MoS 2 nanosheets with extraordinary sodium storage properties via thermal-driven ion intercalation assisted exfoliation of bulky MoS 2

Metallic phase (1T) MoS 2 has attracted enormous attention as an appealing energy storage material for batteries, supercapacitors, and catalysts. However, a facile fabrication method is lacking and the intensive understanding of its sodium storage mechanism is absent. Herein, ultrathin 1T MoS 2 nanosheets (1-2 layers) are directly fabricated via and are investigated as an anode material for sodium-ion batteries. Interestingly, the as-prepared 1T MoS 2 nanosheets demonstrate a high reversible capacity of 450 mAh g -1 at 50 mA g -1 and outstanding cycling stability with a high capacity retention ratio of 94% after 200 cycles at 1 A g -1 , which is far superior to that of the 2H phase counterpart. Density function theory (DFT) calculations show that, in addition to significantly enhanced electronic conductivity, 1T MoS 2 also possesses much more sodium philicity and faster Na atom mobility in comparison with the 2H phase. More importantly, as revealed by ex-situ Raman, in-situ X-ray diffraction, and DFT calculations, the 1T MoS 2 is more capable of suppressing the dissolution of S species from the material structure compared with the 2H phase, leading to excellent cycling stability. Furthermore, the facile and easily scalable method as well as the deep mechanism analysis will provide a very important reference for the development of high-performance MoS 2 anodes and other SIB electrode materials.

1T MoS2↗
DOE OSTI2019

High rate and long cycle life in Li-O 2 batteries with highly efficient catalytic cathode configured with Co 3 O 4 nanoflower

The reaction mechanism of non-aqueous Li-O 2 batteries is based on the deposition and decomposition of Li 2 O 2 . The polarization of Li-O 2 batteries can be rapidly increased by operation under a high rate condition, resulting in the early capacity fade of the cells. Therefore, a well-designed catalyst with a unique structure and excellent catalytic ability is an important way to boost the round-trip performance of Li-O 2 batteries, especially under high current density. In this work, a unique nanoflower structure assembled with Co 3 O 4 nanosheets is synthesized by using 2-methylimidazole (2-MIM) as a structural directing agent. X-ray photoelectron spectroscopy (XPS) and Raman spectra reveal abundant oxygen vacancies on the surface of the Co 3 O 4 nanoflower, which are beneficial for oxygen reduction and evolution reactions and long round-trip lifetime. Density functional theory results demonstrate that Co 3 O 4 catalyst with oxygen vacancies could promote the wetting of Li 2 O 2 on substrate and formation of a Li 2 O 2 nanofilm, thereby boosting the discharge capacity of Li-O 2 batteries. On account of the synergistic effect of abundant oxygen vacancies, the unique structure, and excellent oxygen evolution reaction, Co 3 O 4 nanoflower-based cells could deliver ultralong lifetime of 276 and 248 cycles with a discharge capacity of 1000 mAh g(-1) under charge/discharge current densities of 0.5 A g -1 and 1 A g -1 , respectively. Finally, this study has shed light on a new strategy for catalyst preparation for long lifetime Li-O 2 batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

Toward a high-voltage fast-charging pouch cell with TiO 2 cathode coating and enhanced battery safety

Nickel-rich layered lithium transition metal oxides, LiNi x Co y Mn 1-x-y O 2 , are key cathode materials for high-energy lithium-ion batteries owing to their high specific capacity. However, the commercial deployment of nickel-rich oxides has been hampered by their poor thermostability and insufficient cycle life. In this work full batteries with uncoated and TiO 2 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathodes and graphite anodes are compared in terms of electrochemical performance and safety behavior. The battery using a TiO 2 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode exhibited better cyclic performance at high cutoff voltage. Electrochemical impedance spectroscopy analysis indicated that the TiO 2 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode gave the battery a more stable charge transfer resistance. Transmission electron microscopy demonstrated that TiO 2 coating reduced accumulation of the cathode electrolyte interface layer on the particle surface. Time-of-flight secondary ion mass spectrometry demonstrated that TiO 2 coating markedly enhanced the interface stability of the cathode particle and protected the particle from serious etching by the electrolyte. Accelerating rate calorimetry revealed that the trigger temperature of thermal runaway for the battery using TiO 2 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 as cathode material was 257 °C, which was higher than that of the battery with the uncoated LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode (251 °C). In situ X-ray diffraction during heating demonstrated that this enhanced safety can be attributed to the suppressed phase evolution of the coated cathode material.

25 ENERGY STORAGE↗
DOE OSTI2020

A practical phosphorus-based anode material for high-energy lithium-ion batteries

State-of-the-art lithium-ion batteries cannot satisfy the increasing energy demand worldwide because of the low specific capacity of the graphite anode. Silicon and phosphorus both show much higher specific capacity; however, their practical use is significantly hindered by their large volume changes during charge/discharge. Although significant efforts have been made to improve their cycle life, the initial coulombic efficiencies of the reported Si-based and P-based anodes are still unsatisfactory (<90%). In this study, by using a scalable high-energy ball milling approach, we report a practical hierarchical micro/nanostructured P-based anode material for high-energy lithium-ion batteries, which possesses a high initial coulombic efficiency of 91% and high specific capacity of ~2500 mAh g –1 together with long cycle life and fast charging capability. In situ high-energy X-ray diffraction and in situ single-particle charging/discharging were used to understand its superior lithium storage performance. Moreover, proof-of-concept full-cell lithium-ion batteries using such an anode and a LiNi 0.6 Co 0.2 Mn 0.2 O 2 cathode were assembled to show their practical use. The findings presented here can serve as a good guideline for the future design of high-performance anode materials for lithium-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

Durable hybrid electrocatalysts for proton exchange membrane fuel cells

The low durability of carbon-based non-precious metal electrocatalysts hinders their practical applications in proton exchange membrane fuel cells (PEMFCs). In this study, we rationally design a hybrid Pt-Fe-N-C electrocatalyst with unprecedented durability. It consists of abundant Pt and Fe single atoms homogeneously dispersed on the nitrogen-doped carbon support and a small amount of Pt-Fe alloy nanoparticles. A PEMFC with Pt-Fe-N-C as the cathode shows a larger peak power density (0.75 W cm -2 ) than that with Fe-N-C as the cathode (0.50 W cm -2 ). The remarkable durability of Pt-Fe-N-C is reflected from no noticeable drop in the half-wave potential after 70000 potential cycles between 0.6 and 1.0 V in the liquid cell, and 80% current retention after 85 h of potential hold at 0.4 V in the fuel cell. This work demonstrates the feasibility of improving the durability of Fe-N-C material via ultra-low Pt doping and makes non-precious metal electrocatalysts be close to achieving commercial metrics.

25 ENERGY STORAGE↗
DOE OSTI2021

A General Strategy for Batch Development of High-Performance and Cost-Effective Sodium Layered Cathodes

High-performance and low-cost transition metal (TM) layered oxides using earth abundant elements are promising cathodes for Na-ion batteries. However, it is challenging to obtain desired materials because the large Na size, different Na occupations and various layer stacking sequences multiply the complication in determining the structure of a given composition and exacerbate uncertainty to the structure-property correlation. In this work, we use the attainment of desired NaxMnyNiZTM1-y-zO2-based cathode materials as an example to demonstrate a general roadmap for batch development of sodium layered cathodes towards practical applications. A synthesis phase diagram of NaxMnyNi1-yO2 was created for pre-screening and rational selection of the platform material of P2/O3-structured Na0.85Mn0.6Ni0.4O2. Cationic potential was leveraged in elemental substitution to further promote the material structural stability and electrochemical performance. Several cost-effective O3 and P2/O3 hybrid cathode materials have been obtained, all of which demonstrate excellent performance. In particular, the Na0.85Mn0.5Ni0.4Ti0.1O2 delivers a high specific capacity of ~130 mAh/g between 2-4 V and 91% retention after 500 cycles. The work discovers multiple materials as high-performance and cost-effective Na-ion battery cathodes and offers critical guidance to the rational design of future layered cathode materials.

Xiao, Biwei↗