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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

LiGa(OTf)(sub 4) as an Electrolyte Salt for Li-Ion Cells

Lithium tetrakis(trifluoromethane sulfo - nato)gallate [abbreviated "LiGa(OTf)4" (wherein "OTf" signifies trifluoro - methanesulfonate)] has been found to be promising as an electrolyte salt for incorporation into both liquid and polymer electrolytes in both rechargeable and non-rechargeable lithium-ion electrochemical cells. This and other ingredients have been investigated in continuing research oriented toward im proving the performances of rechargeable lithium-ion electrochemical cells, especially at low temperatures. This research at earlier stages, and the underlying physical and chemical principles, were reported in numerous previous NASA Tech Briefs articles. As described in more detail in those articles, lithiumion cells most commonly contain nonaqueous electrolyte solutions consisting of lithium hexafluorophosphate (LiPF6) dissolved in mixtures of cyclic and linear alkyl carbonates, including ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). Although such LiPF6-based electrolyte solutions are generally highly ionically conductive and electrochemically stable, as needed for good cell performance, there is interest in identifying alternate lithium electrolyte salts that, relative to LiPF6, are more resilient at high temperature and are less expensive. Experiments have been performed on LiGa(OTf)4 as well as on several other candidate lithium salts in pursuit of this interest. As part of these experiments, LiGa(OTf)4 was synthesized by the reaction of Ga(OTf)3 with an equimolar portion of LiOTf in a solvent consisting of anhydrous acetonitrile. Evaporation of the solvent yielded LiGa(OTf)4 as a colorless crystalline solid. The LiGa(OTf)4 and the other salts were incorporated into solutions with PC and DMC. The resulting electrolyte solutions exhibited reasonably high ionic conductivities over a relatively wide temperature range down to 40 C (see figure). In cyclic voltammetry measurements, LiGa(OTf)4 and the other salts exhibited acceptably high electrochemical stability over the relatively wide potential window of 0 to 5 V versus Li+/Li. 13C nuclear-magneticresonance measurements yielded results that suggested that in comparison with the other candidate salts, LiGa(OTf)4 exhibits less ion pairing. Planned further development will include optimization of the salt and solvent contents of such electrolyte solutions and incorporation of LiGa(OTf)4 into gel and solid-state polymer electrolytes. Of the salts, LiGa(OTf)4 is expected to be especially desirable for incorporation into lithium polymer electrolytes, wherein decreased ion pairing is advantageous and the large delocalized anions can exert a plasticizing effect.

Reddy, V. Prakash↗
NASA NTRS2003

Miniature Inchworm Actuators Fabricated by Use of LIGA

Miniature inchworm actuators that would have relatively simple designs have been proposed for applications in which there are requirements for displacements of the order of microns or tens of microns and for the ability to hold their positions when electric power is not applied. The proposed actuators would be members of the class of microelectromechanical systems (MEMS), but would be designed and fabricated following an approach that is somewhat unusual for MEMS. Like other MEMS actuators, the proposed inchworm actuators could utilize thermoplastic, bimetallic, shape-memory-alloy, or piezoelectric actuation principles. The figure depicts a piezoelectric inchworm actuator according to the proposal. As in other inchworm actuators, linear motion of an extensible member would be achieved by lengthening and shortening the extensible member in synchronism with alternately clamping and releasing one and then the other end of the member. In this case, the moving member would be the middle one; the member would be piezoelectric and would be shortened by applying a voltage to it. The two outer members would also be piezoelectric; the release of the clamps on the upper or lower end would be achieved by applying a voltage to the electrodes on the upper or lower ends, respectively, of these members. Usually, MEMS actuators cannot be fabricated directly on the side walls of silicon wafers, yet the geometry of this actuator necessitates such fabrication. The solution, according to the proposal, would be to use the microfabrication technique known by the German acronym LIGA - "lithographie, galvanoformung, abformung," which means lithography, electroforming, molding. LIGA involves x-ray lithography of a polymer film followed by selective removal of material to form a three-dimensional pattern from which a mold is made. Among the advantages of LIGA for this purpose are that it is applicable to a broad range of materials, can be used to implement a variety of designs, including those of structures >1 mm high, affords submicron precision, and is amenable to mass production at relatively low unit cost. Fabrication of the proposed actuators would involve some technological risks - in particular, in the integration of electrode connection lines and placement of actuator elements. It will also be necessary to perform an intensive study of the feasibility of growing piezoelectric crystals onto LIGA molds.

Yang, Eui-Hyeok↗
NASA NTRS1995

Recent Developments in Microsystems Fabricated by the Liga-Technique

As an example of microsystems fabricated by the LIGA-technique (x-ray lithography, electroplating and molding), three systems are described and characterized: a triaxial acceleration sensor system, a micro-optical switch, and a microsystem for the analysis of pollutants. The fabrication technologies are reviewed with respect to the key components of the three systems: an acceleration sensor, and electrostatic actuator, and a spectrometer made by the LIGA-technique. Aa micro-pump and micro-valve made by using micromachined tools for molding and optical fiber imaging are made possible by combining LIGA and anisotropic etching of silicon in a batch process. These examples show that the combination of technologies and components is the key to complex microsystems. The design of such microsystems will be facilitated is standardized interfaces are available.

Schulz, J.↗
DOE OSTI2020

Materials Data on LiGa by Materials Project

LiGa is Zintl Phase structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional and consists of two LiGa frameworks. Li is bonded to four equivalent Ga atoms to form distorted corner-sharing LiGa4 tetrahedra. All Li–Ga bond lengths are 2.71 Å. Ga is bonded to four equivalent Li atoms to form distorted corner-sharing GaLi4 tetrahedra.

36 MATERIALS SCIENCE↗
NASA NTRS2009

Miniature Scroll Pumps Fabricated by LIGA

Miniature scroll pumps have been proposed as roughing pumps (low - vacuum pumps) for miniature scientific instruments (e.g., portable mass spectrometers and gas analyzers) that depend on vacuum. The larger scroll pumps used as roughing pumps in some older vacuum systems are fabricated by conventional machining. Typically, such an older scroll pump includes (1) an electric motor with an eccentric shaft to generate orbital motion of a scroll and (2) conventional bearings to restrict the orbital motion to a circle. The proposed miniature scroll pumps would differ from the prior, larger ones in both design and fabrication. A miniature scroll pump would include two scrolls: one mounted on a stationary baseplate and one on a flexure stage (see figure). An electromagnetic actuator in the form of two pairs of voice coils in a push-pull configuration would make the flexure stage move in the desired circular orbit. The capacitance between the scrolls would be monitored to provide position (gap) feedback to a control system that would adjust the drive signals applied to the voice coils to maintain the circular orbit as needed for precise sealing of the scrolls. To minimize power consumption and maximize precision of control, the flexure stage would be driven at the frequency of its mechanical resonance. The miniaturization of these pumps would entail both operational and manufacturing tolerances of <1 m. Such tight tolerances cannot be achieved easily by conventional machining of high-aspect-ratio structures like those of scroll-pump components. In addition, the vibrations of conventional motors and ball bearings exceed these tight tolerances by an order of magnitude. Therefore, the proposed pumps would be fabricated by the microfabrication method known by the German acronym LIGA ( lithographie, galvanoformung, abformung, which means lithography, electroforming, molding) because LIGA has been shown to be capable of providing the required tolerances at large aspect ratios.

Wiberg, Dean↗
DOE OSTI2020

Materials Data on LiGa(SeO3)2 by Materials Project

LiGa(SeO3)2 crystallizes in the tetragonal I-42d space group. The structure is three-dimensional. Li1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are two shorter (2.01 Å) and two longer (2.03 Å) Li–O bond lengths. Ga3+ is bonded in an octahedral geometry to six O2- atoms. There are a spread of Ga–O bond distances ranging from 1.99–2.03 Å. Se4+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. There are a spread of Se–O bond distances ranging from 1.72–1.75 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Ga3+, and one Se4+ atom. In the second O2- site, O2- is bonded in a trigonal non-coplanar geometry to one Li1+, one Ga3+, and one Se4+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one Ga3+ and one Se4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiGa(PO3)4 by Materials Project

LiGa(PO3)4 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. Li1+ is bonded to four O2- atoms to form distorted LiO4 tetrahedra that share corners with four equivalent PO4 tetrahedra and an edgeedge with one GaO6 octahedra. There are two shorter (1.93 Å) and two longer (2.08 Å) Li–O bond lengths. Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with six PO4 tetrahedra and an edgeedge with one LiO4 tetrahedra. There is four shorter (1.97 Å) and two longer (2.00 Å) Ga–O bond length. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one GaO6 octahedra, corners with two equivalent LiO4 tetrahedra, and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 44°. There are a spread of P–O bond distances ranging from 1.47–1.62 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent GaO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 44–49°. There are a spread of P–O bond distances ranging from 1.51–1.60 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ga3+ and one P5+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two P5+ atoms. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two P5+ atoms. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Li1+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ga3+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Li1+, one Ga3+, and one P5+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1997

A LIGA Fabricated Quadrupole Array for Mass Spectroscopy

A linear array of nine quadrupoles was fabricated using the LIGA process. Pole heights ranging from 1 to 3 mm were fabricated using synchrotron X-ray exposures to form free standing polymethylmethacrylate (PMMA) molds into which copper, gold or nickel were electroplated.

Quadrupole Array synchrotron X-ray↗
DOE OSTI2020

Materials Data on LiGa(SiO3)2 by Materials Project

LiGaSi2O6 is Esseneite structured and crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 2.07–2.54 Å. Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with six equivalent SiO4 tetrahedra and edges with two equivalent GaO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.92–2.15 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent GaO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 37–60°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Li1+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Li1+, two equivalent Ga3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Ga3+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiGa(SiO3)2 by Materials Project

LiGaSi2O6 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Li1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Li–O bond distances ranging from 2.07–2.39 Å. Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent GaO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.92–2.15 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent GaO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–59°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent GaO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 42–60°. There are a spread of Si–O bond distances ranging from 1.61–1.67 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Li1+, one Ga3+, and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Ga3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to one Li1+, two equivalent Ga3+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Li1+, two equivalent Ga3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one Li1+ and two equivalent Si4+ atoms. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiGa(MoO4)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 OSTI2020

Materials Data on LiGa(WO4)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 OSTI2020

Materials Data on LiGa(GeSe3)2 by Materials Project

LiGaGe2Se6 crystallizes in the monoclinic Cc space group. The structure is three-dimensional. Li1+ is bonded in a 4-coordinate geometry to four Se2- atoms. There are a spread of Li–Se bond distances ranging from 2.69–2.90 Å. Ga3+ is bonded to four Se2- atoms to form GaSe4 tetrahedra that share corners with four GeSe4 tetrahedra. There are a spread of Ga–Se bond distances ranging from 2.44–2.46 Å. There are two inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to four Se2- atoms to form GeSe4 tetrahedra that share corners with two equivalent GaSe4 tetrahedra and corners with two equivalent GeSe4 tetrahedra. There are a spread of Ge–Se bond distances ranging from 2.38–2.44 Å. In the second Ge4+ site, Ge4+ is bonded to four Se2- atoms to form GeSe4 tetrahedra that share corners with two equivalent GaSe4 tetrahedra and corners with two equivalent GeSe4 tetrahedra. There are a spread of Ge–Se bond distances ranging from 2.39–2.44 Å. There are six inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to one Li1+ and two Ge4+ atoms. In the second Se2- site, Se2- is bonded in a water-like geometry to two Ge4+ atoms. In the third Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to one Li1+, one Ga3+, and one Ge4+ atom. In the fourth Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to one Li1+, one Ga3+, and one Ge4+ atom. In the fifth Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to one Li1+, one Ga3+, and one Ge4+ atom. In the sixth Se2- site, Se2- is bonded in a water-like geometry to one Ga3+ and one Ge4+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1995

Fabricating Sub-collimating Grids for an X-ray Solar Imaging Spectrometer using LIGA Techniques

This paper describes fabrication of sub-collimating X-ray grids that are used in an instrument for the High Energy Solar Spectroscopic Imager ( HESSI ), a proposed NASA mission that will promote understanding of solar particle acceleration and explosive energy release in the magnetized plasmas at the Sun. The HESSI comprises 12 rotating pairs of high-aspect-ratio, high-Z grids; each pair is separated by 1.7 meters and backed by a single Ge detector.

x-ray↗