Mica Foil Research Articles

Polymer-Garnet-Based Composite Cathodes for Solid-State Li Batteries

All-solid-state lithium batteries (ASSLBs) can potentially outperform conventional Li-ion batteries with liquid or polymer electrolyte. One example for solid electrolytes is the garnet-type oxide Li7La3Zr2O12 (LLZO). LLZO has a wide electrochemical window, stability vs. lithium, and good ionic conductivity at room temperature. The cathode in ASSLBs is manufactured from a cathode active material (CAM), such as LiCoO2 (LCO). The efficiency of Li-ion storage can be improved by the use of a composite cathode consisting from a CAM and an ion-conducting ceramic, e.g. LCO/LLZO. In such a composite cathode, LLZO delivers Li-ions through the whole bulk enhancing the volumetric loading of LCO. In this work the addition of polymer electrolyte into LCO/LLZO composite cathode was proposed, aiming at further increase of cell performance due to facilitation of CAM usage, similar to the approach of manufacturing of polymer-ceramic electrolytes. They are fabricated mostly by tape casting of slurry with polymer matrix, ceramic filler and a solvent. An alternative technology includes free sintering of tape-casted LCO/LLZO porous network and subsequent infiltration by liquid or polymer electrolyte. Free sintering of LCO/LLZO composite requires relatively high temperature and/or long sintering time. This results in loss of volatile Li with decrease in electrochemical performance.In the present work the LCO/LLZO composite cathode was manufactured in a powder-based process by Field-Assisted Sintering Technique also known as Spark Plasma Sintering (FAST/SPS). Fast heating (100°C/min and higher) and application of mechanical pressure during FAST/SPS enable reduction of sintering temperature and processing time needed for fabrication of nearly-fully-dense composite.[1] Thereby, Li evaporation and grain growth can be significantly reduced. This technology was used in our previous work for fabrication of half-cells with dense LLZO electrolyte and dense LCO/LLZO composite cathode. However, the appearance of side phase after sintering at low pressure and a residual porosity was observed. The reason for that was partial reduction of oxides by carbon originated from graphite foil in FAST/SPS setup. In the presented work, the graphite foil was replaced by carbon-free mica foil. This measure enabled FAST/SPS sintering of porous LCO/LLZO network without side phase formation. The obtained porous skeleton was infiltrated with polymer electrolyte to fabricate a polymer-ceramic composite cathode. The cathode was assembled with an anodic half-cell consisting of dense FAST/SPS-sintered LLZO electrolyte and attached indium (In) foil used as anode. The ASSLB with polymer-ceramic composite cathode showed significantly lower interfacial impedance and remarkably higher area-specific storage capacity as compared to the similar ASSLBs with pure ceramic (porous or dense) composite cathodes. Thus, the functionality and the advanced storage capacity of the proposed polymer-ceramic cathode and related ASSLB architecture were demonstrated.[2]

Self-assembly behavior of POSS based ABA type amphiphilic tri-block copolymer prepared via ATRP

A series of ABA tri-block copolymers (TBCPs) of acryloisobutyl POSS (AibPOSS) and tert-butyl acrylate (tBA) with varying block length of poly(tert-butyl acrylate) (PtBA) was prepared via atom transfer radical polymerization (ATRP). PtBA block of these TBCPs, was selectively hydrolyzed to prepare poly(acryloisobutyl POSS)-block-poly(acrylic acid)-block-poly(acryloisobutyl POSS) (PAibPOSS-b-PAA-b-PAibPOSS). Interestingly, this hydrolyzed TBCP showed custard apple like, worm like and brush like morphologies in different block lengths of PAA (PAA90, PAA138 and PAA166) block. In this case, the TBCPs were dispersed in toluene followed by casting on the mica foil and subsequent evaporation, and then their morphologies were analyzed. Depending on the content of PAA, BCPs arranged themselves in spherical and cubical morphology over glass surface when cast with a mixed solvent (THF-water) (1: 4 vol ratio) followed by evaporation. To study the disparity in the particle size with the alternation of the PAA block length in solution, DLS analysis was carried out in THF-water mixture.

Flow and evaporation in single micrometer and nanometer scale pipes

We report measurements of pressure driven flow of fluids entering vacuum through a single pipe of micrometer or nanometer scale diameter. Nanopores were fabricated by etching a single ion track in polymer or mica foils. A calibrated mass spectrometer was used to measure the flow rates of nitrogen and helium through pipes with diameter ranging from 10 μm to 31 nm. The flow of gaseous and liquid nitrogen was studied near 77 K, while the flow of helium was studied from the lambda point (2.18 K) to above the critical point (5.2 K). Flow rates were controlled by changing the pressure drop across the pipe in the range 0–31 atm. When the pressure in the pipe reached the saturated vapor pressure, an abrupt flow transition was observed. A simple viscous flow model is used to determine the position of the liquid/vapor interface in the pipe. The observed mass flow rates are consistent with no slip boundary conditions.

Influence of support materials on carbon clusters formation from fullerene C60 and TOF parameters

In the present paper the effect of different fullerene C60 substrates on the production of positive and negative ions has been examined. The ions were produced by the laser desorption/ionization method (LDI). All measurements were carried out using a linear time of flight mass spectrometer (TOF). Usually stainless steel is a substrate for the tested samples. Silver was also examined. In some cases dielectrics are used as sample substrates. In this work insulating substrates such as mica, glass and floppy disc foil were used. The influence of these different materials on the positive and negative ions mass spectra was observed. During the experiment, the electric charging of dielectric substrates affects the spectrometer: ion time of flight and distribution of potentials inside the ion source.

A Study on the Formation and Thermal Stability of 11-MUA SAMs on Au(111)/Mica and on Polycrystalline Gold Foils

In this article we present a comprehensive study of 11-mercaptoundecanoic acid self-assembled monolayer (SAM) formation on gold surfaces. The SAMs were prepared in ethanolic solution, utilizing two different substrates: Au(111)/mica and polycrystalline gold foils. Several experimental methods (X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and atomic force microscopy) reveal a well-defined SAM. The main focus of this work, however, was to test the stability of these SAMs by thermal desorption spectroscopy. The spectra show different desorption peaks indicating different adsorption states and/or decomposition products on the surface. The assumed monolayer peak, which can be attributed to desorption of the intact molecule, is detected at 550 K. Further desorption peaks can be found, which result, e.g., from cracking of the S-C bond on the surface, depending on the substrate quality and on the residence time under ambient conditions.

Heinz Maier-Leibnitz

Heinz Maier-Leibnitz

Millimeter-wave intracavity-jet OROTRON-spectrometer for investigation of van der Waals complexes

A highly sensitive intracavity millimeter-wave spectrometer was developed for the investigation of the absorption spectra of van der Waals complexes in a supersonic jet. The key element of the spectrometer is a tunable oscillator, called OROTRON, which generates the millimeter-wave radiation through the interaction of an electron beam with the electromagnetic field of a high quality (Q≈104) Fabry–Perot resonant cavity. This cavity consists of a movable spherical mirror and a fixed planar mirror with the periodic structure imprinted on its surface. The electron beam moves along the periodic structure of the plane mirror. This part separated from the rest of the resonator by a mica foil is kept under ultrahigh vacuum conditions. The molecular jet is injected by a pulsed valve into the other part of the resonator. The absorption in the jet is sensitively detected by measuring the electric current in a special collector circuit of the OROTRON. The spectral purity of the OROTRON radiation is 10–15 kHz providing the capability of sub-Doppler spectral resolution without phase locking. An increase in sensitivity of a factor of about 100 in comparison with the usual single pass arrangement was evaluated from the measurements of the absorption lines of the CO rare isotopomers, the Ar–CO and Ne–CO van der Waals complexes. The high sensitivity, wide spectral range, and simple tunability of the spectrometer make it a very efficient tool for the searching of weakly absorbing species in a jet.

Preparation of two uranium glass reference materials for fission-track dating of geological samples

The European Commission produced and certified uranium glass for fission-track dating in 1996 (Reference Material IRMM-540). This material is now out of stock and a project for the preparation of two new reference glasses is underway. The new glasses, containing nominally 15 and 55 mg kg −1 uranium, were prepared from blended oxide powder, and cast using an improved method, which minimised micro-scale defects and optimised the yield. Glass rods were produced which were then cut into discs of 2 mm thickness and 15 mm diameter and subsequently polished. Uranium homogeneity and fission-track stability are critical properties of the glass. An extensive study was carried out to verify the homogeneity by fission-track counting, investigating both within-disc and between disc effects, and to investigate potential track fading due to thermal annealing. No evidence of uranium heterogeneity was detected. The stability study, using an “isochronous” method, in which all measurements are made at the end of exposure to artificial ageing, is still underway. The reference material will be certified for isotopic composition (natural), uranium mass fraction and neutron fluence (one disc out of each set of three will be irradiated, together with a mica foil, to induce fission tracks in a certified fluence). The reference materials will be released as IRMM-540R ( 15 mg kg −1 U) and IRMM-541 ( 55 mg kg −1 U).

Perfluorinated surfactants: properties and applications

Thermodynamic properties of fluorinated surfactants are briefly reviewed and compared with the equivalent protonated compounds. The binary phase diagrams of perfluoro surfactants in solvents such as water, oil and perfluorocarbons have been investigated in detail with attention to the aggregation properties of the surfactants in the different solvents. The critical micellar concentration and the surface tension of the perfluorinated surfactant/solvent mixture have been measured for different classes of perfluoro surfactants. The wetting properties of some of these binary mixtures have been studied for different surfaces including glass, mica and aluminium foil. The ternary (perfluoro surfactant/water and oil) and quaternary (perfluoro surfactant/water/oil and cosurfactant) phase diagrams have been investigated in order to study the formation of isotropic and anisotropic regions and the liquid crystal regions. Rheological measurements on these phases have been performed and related to their physical structure. Particular attention has been devoted to the formation of microemulsions of perfluorinated oil in water and vice versa and to liquid crystal systems. Possible applications of industrial interest of these phase are discussed.

Effect of electron irradiation on the dehydration temperature of muscovite mica

Electron irradiation of muscovite mica causes a change in its dehydration temperature. Thin mica foils are exposed to electrons in the energy region between 20 and 60 keV. A threshold electron energy, above which the irradiation causes an increase in its dehydration temperature, is found between 20 and 25 keV. An electron energy around 45 keV is found to be most effective for increasing the dehydration temperature with a minimum dose. Finally, possible mechanisms are presented to explain the radiation induced change of the dehydration temperature of muscovite mica.

Surface area estimation from the adsorption isotherm gradient at the linear portion by benzene and toluene vapors on mica and aluminum foil samples

Adsorption isotherms of benzene and toluene vapors on mica and aluminum foil samples, whose apparent surface areas were known geometrically, were measured at 30 to 40°C by gravimetry, in order to inspect the relation of the surface area of the samples to the gradient at the linear portion or at the inflexion of the Type II (or Type III) adsorption isotherms to be obtained. The surface areas of the mica and aluminum foil samples having respective geometrical surface areas of 500 and 790 cm 2 were estimated as slightly larger values by about +9 and +7% from the values of the linear portion gradient of the adsorption isotherms obtained (adsorption isotherm gradient method). However, the BET surface area of the aluminum sample by the nitrogen adsorption was 12% larger than the geometrical one. It was shown in this study that the adsorption isotherm gradient method using the benzene or toluene vapor at room temperature may be useful as well as the standard BET method for the estimation of the surface area.

Measurement of the spontaneous-fission disintegration constant of 238U

Large-area muscovite mica foils, previously treated thermally, prepared and chemically pre-etched in HF, were exposed in juxtaposition to uranium cylinders (U 3O 8 density 7.16 g cm −3; 3.3 cm in diameter and 4.0 cm in height), for 0.525 yr. In this period the mica foils registered tracks from the spontaneous fission of 238U nuclei contained in the cylinders as well as a small contribution of induced-fission tracks in uranium. We show that the latter group of fission tracks—induced mainly by cosmic-ray neutrons and by fast neutrons from the spontaneous fissions that take place in the cylinder during the exposure—give rise to an increase of less than 2% in the total number of fission tracks detected by the mica foils. Afterwards the mica foils were properly etched in HF and analysed microscopically. Then, sandwiches of uranium-loaded nuclear emulsion, mica foils and uranium targets were irradiated with slow neutrons. In this irradiation, the nuclear emulsions were used as calibrators of the absolute neutron flux. The mica foils were etched in HF, the emulsions were developed, and both fission-track detectors were observed under a microscope. The uranium-loaded nuclear emulsions were made from gel KO from Ilford Ltd. We measured the uranium-loading by gravimetry and by observing, under a microscope, the uranium alpha-activity. We obtained the following result: λ f = (8.6±0.4) × 10 −17 yr −1.

Nuclear track microfilters made of mica

Production and properties of a new class of microsieves with high resistance to corrosion, chemical attack and temperature is described. At the heavy ion accelerator facility GSI, mica foils of 50 mm diameter and up to 60 μm thickness are irradiated with xenon, lead or uranium ions of specific energies up to 8.5 MeV/amu at preset doses (10 3–10 6 cm −2), making often use of the waste beam from nuclear research experiments. The irradiated foils are etched in hydrofluoric acid to the desired pore diameter. The side length of the rhomboidally shaped pore depends linearly on the etching time and has a Gaussian distribution of fwhm ∼12%. The pore size remains constant throughout the thickness of the filter. For higher porosities multiple holes occur with predictable probability. Application of these well defined microsieves is envisioned in chemical engineering for filtration of hot aggressive liquids, in environmental studies for accurate determination of airborne particles, and in diagnostic medicine for filtration of blood.

Search for long-lived superheavy elements in the reaction systemU238+ 9.6-MeV/nucleonCu63,65

A thick /sup 238/U target has been bombarded with /sup 63//sub,//sup 65/Cu ions at an incident beam energy of 9.6 MeV/nucleon. After radiochemical separations into CdS, HgS, and La-oxalate fractions, a search for evidence of the production of superheavy elements was undertaken using Si surface-barrier detectors and mica foils simultaneously for detection of spontaneous-fission events and high-energy ..cap alpha.. emission. No evidence for the presence of superheavy elements in the samples was found. Upper limits for production cross sections for superheavy elements in each of the three chemical samples, assuming an arbitrary half-life of 100 days and a target thickness equal to the entire reaction range of the incident ions from initial energy to the reaction barrier, are as follows: (a) CdS (Z = 108--115): 1 x 10/sup -34/ cm/sup 2/; (b) HgS (Z = 112): 6 x 10/sup -35/ cm/sup 2/; (c) La-oxalate (/sup 254/Cf): 8 x 10/sup -35/ cm/sup 2/. (AIP)

Determination of Coating Contamination in Coated Fuel Particles

Abstract Uranium contamination in the coating layers of coated fuel particles will adversely affect the operation of high-temperature gas cooled reactors. It is thus of great importance to reduce such contamination introduced in the course of manufacture of the particles, and to this end the need is felt for the establishment of an effective method of determining such contamination. In an attempt to answer this need, a comparative experimental study was undertaken on the alternative techniques of (a) isotope dilution mass spectrometry, (b) fluorometry, (c) α-counting and (d) mica foil method. The fission recoil range in the high density pyrolytic carbon, necessary for the determination by the mica foil method, was estimated experimentally. From the results, it is concluded that α-counting and mica foil methods should mutually complement the shortcomings possessed by each method in determining the contamination of coated fuel particles by kernel material.

The determination of oxygen in copper by α-particle activation analysis

The determination of oxygen in copper by activation analysis with 45-MeV α-particles is described. The chemical separation of 18F produced from oxygen consists of steam distillation as fluosilicic acid, followed by precipitation of the interfering gallium activities as the hydroxide and of the fluoride as lead chlorofluoride or of cation exchange followed by lead chlorofluoride precipitation. This allows a total decontamination from matrix radiation in excess of 10 6. As standard, mica foils are used, while, for the purp̈ose of flux monitoring, the activity induced in a thin copper or mica foil, placed before the sample is counted. Alternatively, the intensity of the particle beam is measured. The method, which allows determination of oxygen at the 1 μg g -1 level with a precision of about 10%, is applied to the determination of a concentration of 1.2 μg g -1. Analysis of a reference material containing 70 μg O g -1 proves the accuracy of the standardization methods applied.

On the selective erasure of cathodochromic image displays

A cathode ray tube is used with a cathodochromic material carried either on a mica foil or on the faceplate of the tube. Some experiments are performed on the selective erasure of information by means of heat applied by electron bombardment. The energy density required to erase a spot and a line is measured. The pulse duration and dwell time are varied between 10 ms and 10 s. The results can be understood by use of the heat flow equation, and can be used to assess the possibility of selective erasure in a given configuration.

A simple, stable Fabry-P rot etalon

The design and construction of a simple mechanical Fabry-Perot etalon is described. Attention to detail is an important feature of etalon design. The elimination of screwed junctions, by manufacturing the etalon body from a solid piece of mild steel, assists freedom from flexure and hence aids the stability of the system. Likewise, frictional drag in the adjusting mechanism has been kept to a minimum. A survey of suitable spacing media in the range 15-200 μm revealed Melinex film (ICI Ltd.) to be superior to wire loops, cleaved mica and metal foil. The interferometer will stay in good adjustment for periods of a few weeks.

Nuclear Energy Levels inB10

Five thousand stereoscopic pictures of electron tracks in a cloud chamber yielded six hundred sixty-five Compton electrons from a thin mica foil and seventy-six \ifmmode\pm\else\textpm\fi{} electron pairs formed in the gas in the chamber. These data indicate thirty-one lines in the $\ensuremath{\gamma}$-ray spectrum of ${\mathrm{B}}^{10}$. Nine energy levels account for the observed lines in a satisfactory manner, and are not in disagreement with the neutron spectrum from the same reaction. An attempt to correlate the observed energy levels with those predicted by theory leads to the following suggested classification: $^{3}S_{1}$ as the ground state (relative energy zero); $^{3}D_{123}$ at 0.26, 0.50 and 0.61 Mev; $^{1}S$ at 1.44 Mev; $^{1}D$ at 1.93 Mev; $^{3}D$ at 2.92 Mev; and $^{1}D$ at 3.64 Mev; and $^{3}F$ at 4.73 Mev.

The Gamma-Ray Spectrum ofB10

The gamma-rays from ${\mathrm{B}}^{10}$, produced by bombarding beryllium with 1 Mev deuterons, have been investigated by an examination of the momentum distribution of Compton electrons ejected from a thin mica foil in an expansion chamber. This spectrum consists of six gamma-rays of energies 0.51, 1.07, 1.44, 1.96, 2.81 and 3.21 Mev. These gamma-rays result from all possible transitions between three excited levels and the ground state of ${\mathrm{B}}^{10}$. The energy levels determined are in agreement with those obtained from a study of the neutron spectrum emitted by the same reaction.