Excess Energy Density Research Articles

Packaging Design and Assembly for Ultrahigh Energy Density Microbatteries

For commercially available lithium ion batteries, the package structures can accounts for as much as 70 percent of its volume. In a multi-year effort, we have developed designs, fabrications, and assembly processes for ultrahigh energy density micro batteries of 5 and 1 cubic millimeter. Over the course of the research, the packaging system evolved due to changes or limitation specific to the battery system itself. During the study, improvements in the construction of the housing for the cathodes were made. Anodized aluminum cans fabricated through our in-house micro-machining facility replaced the electroformed gold cans used in earlier experiments. Throughout the iteration of the can design, a flange around its open end, which would be used for sealing, was present, and both designs were fabricated as arrays. The ability to fabricate the housings in an array format lends it to be implemented into a scalable production assembly process. Materials evaluated for the cover ranged from copper foil to the final design of metalized sapphire with a plated though via. One area which needed to be addressed was reducing the temperature of the assembly process due to a change in the cell materials. This resulted in developing a low temperature hermetic sealing process. The seal between the cover and can was made using a novel composite ring of indium and epoxy. The indium provided the hermeticity needed for the battery chemistry and the epoxy provided mechanical robustness. Most of our experience was with sealing temperatures of 100°C, but the sealing temperature is only limited by the cure temperature of the epoxy. One experiment was conducted to look at the reliability of the seal. A dozen one cubic-millimeter cells were filled with lithium and sealed. They were aged in laboratory ambient environment and periodically weighed. There was no weight gain in any of the cells over the course of several months, but one cell which was opened at the end of the experiment rapidly gained weight as the lithium corroded. The micro-battery cell developed in this program used a lithium cobalt oxide cathode in the form of a porous sintered compact. Its bottom surface was coated with a gold film so that it could be thermocompression bonded to a gold bump on the bottom of the can. Following bonding, the cathode assembly was spray coated with a polymer separator. The anode was a piece of lithium metal bonded to the battery cover. After the cover was sealed to the battery can, the cell was filled with electrolyte and charged. Then a plug was inserted in the via through the cover to seal the battery. Batteries assembled in this manner exhibited energy densities in excess of 200 Wh/l for the smaller volumetric package.

Density-functional theory of thermoelectric phenomena.

We introduce a nonequilibrium density-functional theory of local temperature and associated local energy density that is suited for the study of thermoelectric phenomena. The theory rests on a local temperature field coupled to the energy-density operator. We identify the excess-energy density, in addition to the particle density, as the basic variable, which is reproduced by an effective noninteracting Kohn-Sham system. A novel Kohn-Sham equation emerges featuring a time-dependent and spatially varying mass which represents local temperature variations. The adiabatic contribution to the Kohn-Sham potentials is related to the entropy viewed as a functional of the particle and energy density. Dissipation can be taken into account by employing linear response theory and the thermoelectric transport coefficients of the electron gas.

High Temperature Performance of Oxide Film Capacitors

Film capacitors that perform well at temperatures exceeding 150°C and have energy densities in excess of 1 J/cm3 are an enabling technology for many applications in automotive, geophysical exploration, aerospace, and the military. To address this need Faradox Energy Storage, Inc. has produced and is testing high temperature film capacitors fabricated using amorphous oxides (OxFilm™) as the dielectric material. The capacitors are made by depositing thin films of an oxide dielectric on both sides of a double metalized polyimide substrate to form dielectric-coated electrodes. Currently Faradox is producing 2″ long, 1/4″ diameter 2 uF, 100 VDC capacitors using silicon dioxide as the dielectric material. In this paper we present test data demonstrating that OxFilm capacitors have relatively stable properties over a wide temperature range. Measurements include capacitor testing at different 3rd Party test facilities and internal testing using a variety of test conditions including:Life testing at 200 and 250°C for over 1000 hours with measurements of capacitance, leakage, dF and ESR.Capacitance versus voltage, temperature and frequencyImpedance, ESR, and dF versus frequency and temperature and voltageData will also be presented that show these capacitors can be cycled between 0°C and 200°C without degrading their performance. Work is ongoing to obtain additional test data with more statistically significant numbers of capacitors.

Research on Crack Generating in the Process of Hybrid Plasma and Laser Deposition Manufacturing

Crack is the common drawback in deposition manufacturing process with high energy beam, which usually leads to the manufacturing process being given up halfway. So it is important and urgent to investigate the generating principle of crack and establish relative means to prevent crack appearance. In this paper, the principle of crack generating in the process of hybrid plasma and laser manufacturing was studied experimentally and systematically. The influences of power system and shielding atmosphere on crack were researched. The results were summarized as follows: (1) The crack generating in the course of manufacturing is mainly heat crack. (2) Excessive energy density and temperature will result in crack. (3) The best method preventing part being manufactured from oxidation is to put the whole part into the inert gas.

Specific heat, internal energy, and thermodynamic Casimir force in the neighborhood of theλtransition

We discuss the relation of the specific heat, the energy density and the thermodynamic Casimir effect in the case of thin films in the three dimensional XY universality class. The finite size scaling function $\theta(x)$ of the thermodynamic Casimir force can be expressed in terms of the scaling functions h'(x) and h(x) of the excess energy density and the excess free energy density. A priori these quantities depend on the reduced temperature t and the thickness L_0 of the film. However finite size scaling theory predicts that the scaling functions depend only on the combination x=t [L_0/\xi_0]^{1/\nu}, where \nu is the critical exponent and $\xi_0$ the amplitude of the correlation length. We exploit this fact to compute \theta from Monte Carlo data for the excess energy density of the improved two-component \phi^4 model on the simple cubic lattice with free boundary conditions in the short direction. We repeat this exercise using experimental data for the excess specific heat of 4He films. The finite size scaling behaviour of the excess specific heat is governed by h''(x), which is proportional to the scaling function $f_2$ discussed in the literature. We compare our results with previous work, where the Casimir force has been computed by taking the derivative of the excess free energy with respect to the thickness of the film. As a preparative study we have also computed the scaling functions h'(x) and h(x) for finite L^3 systems with periodic boundary conditions in all directions, where L is the linear extension of the system.

Alkali-free glass as a high energy density dielectric material

One of the greatest challenges in the development of new high energy density materials is to increase dielectric permittivity while maintaining high breakdown strength. The dielectric breakdown behavior of an alkali-free barium boroaluminosilicate glass is shown to have remarkably high DC dielectric breakdown strength (12 MV/cm) and reasonably high permittivity (~ 6), equating to energy densities in excess of 35 J/cm 3. This behavior is attributed to highly polarizable Ba ions enhancing the real part of complex permittivity, the low loss due to the alkali-free composition, and the substantially defect-free quality of the glass and its surfaces. To our knowledge, this is the highest breakdown strength reported for a bulk glass, and rivals the breakdown strength more typically observed in pristine thin films of SiO 2. These findings indicate that alkali-free multicomponent glasses may be strong candidates for next-generation high energy density storage capacitors for portable or pulsed power applications.

Accretion disc dynamos opened up by external magnetic fields

We show that a relatively weak poloidal external magnetic field, imposed in the outer parts of a Keplerian accretion disc, can open magnetic lines of a much stronger magnetic field generated by the dynamo in the inner disc. The resulting magnetic configuration can be favourable for launching a centrifugally driven wind. Even for a relatively weak external magnetic field (with energy density in excess of about only 10% of the thermal energy density at the outer disc radius) the geometry of the poloidal field in the disc neigbourhood is almost independent of the dynamo action, and is determined by the external field. The radial profile of the poloidal magnetic field on the disc surface is similar to that in the self-similar solution of Blandford & Payne (\cite{BP82}). We conclude that poloidal fields resulting from dynamo action can be important for launching a magneto-centrifugally driven outflow in accretion discs that occur in weakly magnetized environments, i.e. where an external field is too weak to be important. However, even a relatively weak external field can be wound up by the differential rotation to give a much stronger azimuthal field, and so modify dynamo action in the disc.

Memory of texture during HDDR processing of NdFeB

The hydrogenation disproportionation desorption recombination (HDDR) process can yield highly anisotropic and coercive NdFeB-type powders with energy densities in excess of (BH)/sub max/ = 340 kJ/m/sup 3/. The elucidation of the very unusual phenomenon of texture inducement is of great scientific and technological interest. Here, Nd/sub 12.5/Fe/sub bal/B/sub 6.3/ and Nd/sub 12.5/Fe/sub bal/Ga/sub 0.3/Nb/sub 0.3/B/sub 6.3/ alloys have been processed and hydrogen partial pressures and dwell times during disproportionation and recombination have been varied systematically. The effect of these processing parameters on the microstructural and magnetic properties is described. Intermediate processing stages were characterized by Rietveld analysis, field emission gun scanning electron microscopy, transmission electron microscopy using EDX and diffraction modes. Crystallographic relationships between parent, disproportionated and recombined phases are described and it is suggested that the iron boride phase could act as the anisotropy-mediating phase throughout the different stages of the process. The nucleation and growth of the various phases are controlled by the hydrogen partial pressure during the exothermic disproportionation, thereby strongly effecting the final degree of texture. This d-HDDR (dynamic-) process yields a highly stable memory carrier, thus, allowing to maximize texture without Co addition. It is proposed that Nb is useful for the stabilization of the boride phase, whereas Ga is beneficial during initial recombination.

大面積電子ビームによる金型加工面の高能率仕上げに関する研究（第１報）―放電加工面平滑化の可能性と基本的加工特性の解明―

A new finishing process for metal molds by large-area electron beam irradiation is proposed in this study. In the large-area electron beam irradiation equipment used here, the electron beam with a maximum diameter of 60mm can be used for melting or evaporating metal surface. Experimental results show that the roughness of the irradiated surface becomes smaller with increasing the energy density of beam and the number of irradiation, but excessive energy density and too many irradiations make it a little worse. Under a proper condition, the surface roughness decreases from 6μm to less than 1 μm in just a few minutes. The glossiness of the surface also can be improved very well. By observing the cross section of irradiated surfaces, it is confirmed that the material removal is performed just on the irradiated surface without any resolidified layers. Moreover, the surface roughness after irradiation becomes smaller when the roughness before irradiation is small. Therefore, large-area electron beam irradiation method has a high possibility of high efficient finishing process for metal molds.

Advanced rechargeable sodium batteries with novel cathodes

Various high energy density rechargeable batteries are being considered for future space applications. Of these, the sodium-sulfur battery is one of the leading candidates. The primary advantage is the high energy density (760 W h kg −1 theoretical). Energy densities in excess of 180 W h kg −1 have been realized in practical batteries. More recently, cathodes other than sulfur are being evaluated. We, at JPL, are evaluating various new cathode materials for use in high energy density sodium batteries for advanced space applications. Our approach is to carry out basic electrochemical studies of these materials in a sodium cell configuration in order to understand their fundamental behaviors. Thus far, our studies have focussed on alternative metal chlorides such as CuCl 2 and organic cathode materials such as TCNE.

An interpretation of the excess energy density observed on the Wien side of the microwave background radiation

Le spectre du rayonnement de fond microonde s'ecarte passablement de la loi de corps noir simple (Matsumoto et al., 1988) pour les frequences elevees. On montre ici qu'un modele constitue d'une loi de corps noir et d'une loi de corps gris permet de decrire correctement le spectre observe. Les implications de cette interpretation sur la conception de l'univers primordial sont discutees

The Roles of Energetic Displacement Cascades in Ion Beam Modifications of Materials

AbstractThe roles of energetic displacement cascades are ubiquitous in the fields of radiation damage and ion beam modifications of materials. These roles can be described on two time scales. For the first, which lasts ≈ 10-11 s, small cascade volumes are characterized by large supersaturations of point defects, structural disorder, and energy densities in excess of some tenths of eV's per atom. During this period, the system can be driven far from equilibrium with significant rearrangement of target atoms and the production of Frenkel pairs. Experimental studies of ion beam mixing in conjunction with molecular dynamics computer simulations, have contributed largely toward understanding these dynamic cascade processes. At later times, the microstructure of the material evolves as cascades begin to overlap, or at elevated temperatures, point defects migrate away from their nascent cascades. It will be shown how the primary state of damage in cascades influences this microstructural development. Examples involving radiation-enhanced diffusion and ion-induced amorphization will be discussed.

Thermomechanical equilibrium in solid-fluid systems with curved interfaces

A virtual variational approach for deducing the conditions for thermomechanical equilibrium is extended to solid-fluid systems with curved interfaces. A surface excess energy density is introduced which depends on excess entropy, number densities of the excess constituent components, the surface deformation gradient, the surface orientation and the principal curvatures. The coupling and roles of the surface stress and the Cahn–Hoffman ξ-vector in stressed solid-fluid systems is identified. Results are used to examine the case of a solid isotropic sphere immersed in a fluid.

Broadband Tunable XeF (C→A) Excimer Laser

In this paper the factors controlling the performance of an electron beam pumped broadband diatomic raregas halide excimer laser are discussed. Particular attention is directed toward the blue/green in the XeF (C-A) laser centered at 485 nm, for which significantly improved performance has been obtained by selective tailoringof mixture kinetic processes. Maximum XeF (C-A) laser output energy densities in excess of 3 J/liter have beenachieved, corresponding to an intrinsic efficiency of approximately 2%.

Efficient XeF(C→A) laser oscillation using electron-beam excitation

Significantly improved XeF(C→A) laser energy density and efficiency have been obtained using electron-beam excited Ar-Xe gas mixtures at pressures up to 10 atm which contain both NF3 and F2. Maximum blue-green laser pulse energy density in excess of 1.0 J/liter was obtained, corresponding to an intrinsic electrical-optical energy conversion efficiency estimated to be in the 0.5%–1.0% range. Comprehensive, time-resolved absolute measurements of XeF(C→A) fluorescence, laser energy, and gain were carried out for a wide variety of experimental conditions. Analysis of these data has resulted in identification of the dominant transient absorbing species in the laser medium. For the laser mixtures investigated in this work, the primary blue/green absorption processes have been identified as photoionization of the 4p, 3d, and higher lying states of Ar, and of the Xe 6p and 5d states, and photodissociation of Ar2(3∑+u) and Ar+3.

Rechargeable high voltage low temperature molten, salt cell Na/β''-alumina/SCl 3+ in AlCl 3-NaCl

This paper deals with the rechargeable molten salt cell: Na/β''-alumina/SCl 3 + in AlCl 3-NaCl, and its underlying chemistry. This cell is operated at 180–250°C, and is characterized by two discharge plateaus: 4Na + SC1 3AlCl 4 + 3AlCl 3 = S + 4NaAlCl 4 2Na + S + AlCl 3 = AlSCl + 2NaCl The AlCl 3-NaCl melt is important in stabilizing several sulfur species formed in charge/discharge processes and in maintaining a conducting liquid positive mixture. The cell voltage in the fully charged state is ⪢ =4.30 V for the first step and 2.75 V for the second step. The theoretical capacity is in excess of 190 Ah kg −1 , corresponding to a theoretical energy density in excess of 700 Wh kg −1. High energy and power densities have been achieved. Hundreds of deep charge/discharge cycles have been obtained for several cells using Reticulated Vitreous Carbon or tungsten positive current-collectors.

Universal and nonuniversal critical behavior of then-vector model with a defect plane in the limitn→∞

The local critical behavior of the $d$-dimensional $n$-vector model near an internal $d\ensuremath{-}1$ dimensional plane of weakened interactions in the limit $n\ensuremath{\rightarrow}\ensuremath{\infty}$ changes qualitatively at $d=3$. For $d>3$ the critical exponent ${\ensuremath{\eta}}_{\ensuremath{\parallel}}$, which characterizes the correlation of spins in the defect plane, is universal, i.e., is independent of the strength of the interactions in the defect plane. We argue that ${\ensuremath{\eta}}_{\ensuremath{\parallel}}$ is nonuniversal for $d=3$ and calculate its dependence on the difference between the defect and bulk couplings to second order in perturbation theory. We show that the excess energy density at a distance $z$ from the defect plane decays at the critical point to the bulk value as ${z}^{\ensuremath{-}2}$ for $d\ensuremath{\ge}3$ and faster than ${z}^{\ensuremath{-}2}$ for $d<3$. Near the free surface of a semi-infinite system one finds a ${z}^{\ensuremath{-}2}$ dependence for $d>3$ as well as for $d\ensuremath{\ge}3$.

Pulsed XeCl laser annealing of ZnS:Mn thin films

We describe pulsed XeCl (308 nm) laser annealing of ZnS thin films implanted with Mn ions and deposited onto single-crystal Si substrates. Successful annealing of the films only occurs when the specimens are held under inert gas pressure of several atmospheres during the laser pulse in order to obtain melting and regrowth of the films without appreciable vaporization. Typically, specimens annealed under 90 pounds per square inch, gauge (psig) of Ne at laser energy densities in excess of ∼0.8 J cm−2 exhibit a higher Mn photoluminescence signal than comparable samples thermally annealed at 500 °C, the difference being a factor of ∼2 at 2.5 J cm−2. Evidence for increased crystallinity in these specimens after laser annealing has also been obtained.

Raman Scattering Characterization of Bonding Defects in Silicon

ABSTRACTRaman scattering is used for the characterization of defects in Si. Damage is produced in single crystal silicon by ion-implantation of As and Si. The phonon structure of the damaged layer is that of the typical amorphous Si. After irradiation by pulsed laser(10ns,532nm) at energy density of approximately 0.1J/cm2, a Raman peak appears at a frequency between 508 cm−1 and 517 cm−1 depending on implant dosage. The higher the implant dosage, the lower is the frequency. We explain this in terms of the residual bonding defects caused by the presence of extraneous atoms such as oxygen. On the other hand, irradiation at an energy density in excess of 0.5 J/cm2, a Raman peak appears at a frequency close to that of the single crystal except for small shifts due to Fano-shift. For implant dosage in excess of 4×1016 As/cm2 , we have found additional peaks at 222 cm−1 and 267 cm−1 which are close to the metallic arsenic modes indicating the presence of arsenic clusters.

Segregation Effects in Cu-Implanted Si after Laser-Pulse Melting

Cu-implanted Si crystals were irradiated with $Q$-switched ruby-laser single pulses. After irradiation with energy density in excess of 1.0 J/${\mathrm{cm}}^{2}$, the Cu atoms accumulate at the sample surface. Thermal annealing in the 500-800\ifmmode^\circ\else\textdegree\fi{}C range casues a migration of Cu inside the specimen, in agreement with diffusion coefficient and solid solubility values. The results indicate the formation of a liquid layer induced by laser irradiation. The solid-liquid interface movement during freezing qualitatively justifies the observed surface accumulation.