Rhenium Foil Research Articles

Half-life of the 188-keV isomer of Re184

We report a new half-life measurement of the 188-keV isomeric state in $^{184}\mathrm{Re}$. The $^{184m}\mathrm{R}\mathrm{e}$ isomer was produced by means of neutron activation of natural rhenium foil in the MARIA nuclear reactor at the National Centre for Nuclear Research (NCBJ). The observation of the $^{184m}\mathrm{R}\mathrm{e}$ decay for over two half-life periods has yielded the new value of ${T}_{1/2}=177.25\ifmmode\pm\else\textpm\fi{}0.07$ d. Our result is the most precise determination of the half-life of the $^{184m}\mathrm{Re}$ isomer and improves the precision of the previously known value of ${T}_{1/2}=169\ifmmode\pm\else\textpm\fi{}8$ d by two orders of magnitude.

A double-layer heating method to generate high temperature in a two-stage multi-anvil apparatus**Project supported by the National Natural Science Foundation of China (Grant No. 51872189) and the Fundamental Research Funds for the Central Universities, China (Grant No. 2018SCUH0022).

A new heating method is proposed to increase the cell temperature of the 6–8 type multi-anvil apparatus without reducing the volume of the sample chamber. The double-layer heater assembly (DHA) has two layers of heaters connected in parallel. The temperature of the cell was able to reach 2500 °C by using 0.025 mm rhenium foils, and the temperature limit was increased by 25% compared with that of the traditional single-layer assembly. The power–temperature relationships for these two assemblies with different sizes were calibrated by using W/Re thermocouple at 20 GPa. When the volume of samples was the same, the DHA not only attained higher temperature, but also kept the holding time longer, compared to the traditional assembly. The results of more than ten experiments showed that the new 10/4 DHA with a relatively large sample size (2 mm in diameter and 4 mm in height) can work stably with the center temperature of the sample cavity exceeding 2300 °C under the pressure of 20 GPa.

The Oxidation of Rhenium and Identification of Rhenium Oxides During Catalytic Partial Oxidation of Ethylene: An In-Situ XPS Study

Abstract Rhenium is catalytically active for many valuable chemical reactions, and consequently has been the subject of scientific investigation for several decades. However, little is known about the chemical identity of the species present on rhenium surfaces during catalytic reactions because techniques for investigating catalyst surfaces in-situ – such as near-ambient-pressure X-ray photoemission spectroscopy (NAP-XPS) – have only recently become available. In the current work, we present an in-situ XPS study of rhenium catalysts. We examine the oxidized rhenium species that form on a metallic rhenium foil in an oxidizing atmosphere, a reducing atmosphere, and during a model catalytic reaction (i.e. the partial-oxidation of ethylene). We find that, in an oxidizing environment, a Re2O7 film forms on the metal surface, with buried layers of sub-oxides that contain Re4+, Re2+ and Re δ+ (δ ∼ 1) species at the Re2O7/Re interface. The Re2+ containing sub-oxide is not a known bulk oxide, and is only known to exist on rhenium-metal surfaces. The Re2O7 film sublimes at a very low temperature (ca. 150 ℃), while the Re4+, Re2+ and Re δ+ species remain stable in oxidizing conditions up to at least 450 ℃. In a reducing atmosphere of H2, the Re2+ species remain on the surface up to a temperature of 330 ℃, while Re δ+ species can be detected even at 550 ℃. Under conditions for partial-oxidation of ethylene, we find that the active rhenium catalyst surface contains no bulk-stable oxides, but consists of mainly Re2+ species and small amounts of Re4+ species. When the catalyst is cooled and inactive, Re2O7 is found to form on the surface. These results suggest that Re2+ and Re4+ species may be active species in heterogeneous rhenium catalysts.

Thermal diffusivity measurement in a diamond anvil cell using a light pulse thermoreflectance technique

Apparatus to measure the thermal diffusivity of a plate between diamond anvils at high pressure was developed. The Mg(OH)2 plates coated with Pt films on both sides were used for testing the apparatus. One side of the Pt film played the role of an absorber of a laser pulse, and the other side was used for the detection of the temperature change. The sample was loaded into a hole drilled in a rhenium foil gasket together with the insulation layers of NaCl as a pressure medium. Subsequently, the sample was compressed with 150 µm culet beveled diamond anvils. The pressure in this study reached 57 GPa. Then, a front face of the sample was heated by laser pulses with a duration of 2 ns and a wavelength of 1064 nm. To probe the temperature change at the back face of the sample, a continuous wave laser beam with a wavelength of 782 nm was irradiated. Using the reflected intensity of the continuous wave laser beam, a transient temperature curve was measured when the heat transferred across Pt/Mg(OH)2/Pt layers. The thermal diffusivity of Mg(OH)2 was calculated by analyzing the transient temperature curves. The thermal diffusivity of Mg(OH)2 is 5.9 × 10−6 m2 s−1 at 57 GPa, which is larger than that at ambient pressure by a factor of ≈6.

Novel rhenium gasket design for nuclear resonant inelastic x-ray scattering at high pressure

For the first time, a highly absorbing element, rhenium, has been proven to be a strong, reliable, and safe gasket material for achieving high pressure in nuclear resonant inelastic x-ray scattering (NRIXS) experiments. Rhenium foil was cut into rectangular slices and in order to reduce absorption, the elevated imprint due to preindenting of the gasket is removed using electrical discharge machining. By utilizing this novel gasket design, transmission losses were mitigated while performing NRIXS experiments conducted on the 119Sn and 57Fe Mössbauer isotopes.

Field emission studies of pulsed laser deposited [formula omitted] films on W and Re

Lanthanum hexaboride films were grown on tungsten and rhenium tips and foils by pulsed laser deposition. The X-ray diffraction spectra of the PLD LaB 6 films on both the substrates show crystalline nature with average grain size ∼ 125 nm . The field emission studies of pointed and foil specimens were performed in conventional and planar diode configurations, respectively, under ultra-high vacuum condition. An estimated current density of ∼ 1.2 × 10 4 A / cm 2 was drawn at the electric field of 3 × 10 3 and 6 × 10 3 V / μ m from the LaB 6 coated tips of tungsten and rhenium, respectively. The Fowler–Nordheim plots were found to be linear showing metallic behavior of the emitters. The field enhancement factors were calculated from the slopes of the Fowler–Nordheim plots, indicating that the field emission is from LaB 6 nanoscale protrusions present on emitter surfaces. The emitters were operated for long time current stability (3 h) studies. The post-field emission surface morphology of the emitters showed no significant erosion of LaB 6 films during 3 h continuous operation. The observed behavior indicates that it is linked with the growth of LaB 6 films on W and Re. These results reveal that the LaB 6 films exhibit high resistance to ion bombardment and excellent structural stability and are more promising emitters for practical applications in field emission based devices.

Rhenium-cup, in-torch vaporization (ITV) sample introduction for axially viewed ICP-AES and its application to the analysis of a microscopic, ng-weight solid sample

A reported advantage of axial over radial plasma viewing is improvement of detection limits. In an attempt to capitalize on this advantage, a new, horizontally operated in-torch vaporization (ITV) sample introduction system was developed and was coupled to an axially viewed inductively coupled plasma-atomic emission spectrometry (ICP-AES) instrument. In ITV, a sample is placed into a cup made out of a thin rhenium (Re) foil and the sample-carrying cup is inserted in a small volume vaporization chamber that clips onto a typical ICP torch. The effect of carrier gas (Ar–∼3% H2) flow rate and cup insertion position on analyte emission characteristics was examined for several elements (e.g., Ba, Be, Ca, Cd, Mg, V, Pb and Zn) that had different vaporization characteristics and emission lines that covered a wide spectral range (e.g., from 213.856 to 455.403 nm). Calibration curves were linear over the (narrow) range of concentrations used in this work and precision ranged between 1.0 and 2% (peak height) and between 1.0 and 4.6% (peak area). Detection limits were in the pg range for Pb, Cd and Zn, in the sub-pg range for Ba, Mg and V, and in the fg and sub-fg range for Be and Ca. The improvement in detection limits enabled determinations of Ca and Mg in microscopic individual grains of pollen (10 pL volume, ∼8 ng weight).

Electrodeposition of Rhenium onto Oriented Rhenium Foils from Salt Melts1

Epitaxial growth of rhenium layer electrodeposited from chloride melts onto single-crystal and polycrystalline rhenium substrates with orientations (10-10), (11-20), and (0001) was studied. Conditions for epitaxial growth on single-crystal rhenium foil with orientation (0001) were found. The surface morpholgy of rhenium deposits was studied and microhardness of single-crystal and polycrystalline rhenium layers with orientation (0001) was measured.

Ultratrace determination of thulium by laser-excited atomic fluorescence spectrometry with atomization in a rhenium lined tube furnace

In the present work, a method for the determination of ultratrace levels of thulium by laser induced atomic fluorescence (LEAFS) was developed. High sensitivity was achieved by using a dye laser pumped by a high repetition copper vapor laser and electrothermal atomization (ETA) in a tube furnace. Four different atomizer surfaces (pyrolytic graphite, tungsten, tantalum and rhenium) as well as coating treatments of the graphite with noble metal solutions were evaluated with the objective of improving the atomization efficiency of thulium. The best results in terms of intensity, reproducibility and lifetime were obtained with rhenium-lined graphite tubes. Since the rhenium surface was more resistant to oxidation under the operational conditions, the sample was atomized under a stop flow regime rather than in an argon miniflow regime, which was required when tantalum and tungsten foils were employed. Atomization under the stop flow regime avoided dilution of the analyte in the analytical zone, thereby improving sensitivity. In addition, the lifetime of the rhenium foil lined atomizer was longer than those observed with tantalum or tungsten linings. Furnace parameters were optimized to maximize the fluorescence signal–background ratio. The limit of detection for the rhenium lined atomizer was 200 fg with a precision of 6.0% at the 10 ng ml −1 level. Thulium was determined with excellent results in urine and coal fly ash samples using the new method.

Diamond-Like Carbon Coatings for Rhenium Wire and Foils

ABSTRACTDiamond like carbon has been deposited as a protective layer for coronary stenting applications. Taking advantage of DLC's resistance to chemical attack, its flexibility, and other properties. our current technical objective is to develop DLC as a coating for radioactive rhenium stents. Radioactive rhenium stents are being investigated to limit smooth muscle cell growth following coronary surgery. The DLC coating is being investigated to reduce the release of radioactive rhenium (released activity) into the blood following the stenting procedure. An inductively coupled RF plasma system was used to deposit the DLC onto rhenium substrates. Foils, wires, and coils were coated and tested for adhesion, cytotoxicity, and release of radioactive rhenium. Our initial results indicate up to a three-fold decrease in released activity relative to uncoated rhenium

Status of the rhenium beta experiment for neutrino mass study

The status of the Genoa 187Re β experiment, the final objective of which is to place limits on the mass of the electron anti-neutrino, will be presented. The latest measurements from a rhenium detector, composed of a NTD-Ge thermistor coupled to a small polycrystalline rhenium foil, will be discussed. An investigation of the expected final experimental performances using Monte Carlo stimulation is also reported.

Defects in fabrication and properties of rhenium foils

Defects in fabrication and properties of rhenium foils

Measurement of melting temperatures of some minerals under lower mantle pressures

Melting temperature measurements of six minerals (stishovite (SiO2), corundum(Al2O3), diopside (CaMgSi2O6), and three perovskites (MgSiO3, CaSiO3, Mg3Al2Si3O12)) at high pressures were carried out in a YAG laser‐heated diamond anvil cell with rhenium metal as an absorber of the laser light. A polished or compressed disc of the sample was in contact with rhenium foil and heated by conduction. Melting was determined by plotting laser power/sample temperature function and looking for the thermal anomaly associated with the fusion of materials. All these solids were found to be highly refractory, requiring quite high temperatures for melting at the lower mantle pressures. The experimental melting results showed that for these minerals, melting temperatures increased with increasing pressure. Our results at low pressures are consistent with the data determined by other techniques (piston‐cylinder, multianvils). The high‐pressure melting of MgSiO3 perovskite agreed with the recent measurements by Zerr and Boehler (1993) within experimental uncertainties. Melting temperatures and melting slopes of CaSiO3 and Mg3Al2Si3O12 perovskites were found to be less than those of MgSiO3 perovskite, indicating that the presence of Ca and Al would decrease the melting temperatures of MgSiO3 perovskite in the Earth's lower mantle and that this effect will increase with increasing pressures. Melting temperature measurements on stishovite and corundum to pressures of 36 GPa and 25 GPa, respectively, are reported.

Transformation of Platinum into a Stable, High-Temperature, Dehydrogenation-Hydrogenation Catalyst by Ensemble Size Reduction with Rhenium and Sulfur

The effect of the addition of rhenium and sulfur on the catalytic properties of platinum and on its ability to resist deactivation by carbonaceous deposits was studied. The reactions of neopentane (2,2-dimethylpropane), n-hexane, and cyclohexane in excess H2 were studied on model bimetallic catalysts prepared by the deposition of platinum on a rhenium foil or vice versa. The rates were measured in a batch reactor with a ratio of H2 to hydrocarbon of 30 or 60, a H2 pressure of 450 kPa, and a reaction temperature in the range of 570 to 800 K. Rhenium-sulfur is catalytically inactive and acted only as a diluent to platinum. As the platinum ensembles on the surface became smaller by dilution with rhenium-sulfur, the rates of the structure-sensitive reactions decreased rapidly and eventually only hydrogenation-dehydrogenation reactions were observed. Most importantly, as the size of the platinum ensembles decreased, they became more resistant to poisoning than the larger ones.

Ensemble size reduction by rhenium-sulfur as a method to lower the rate of deactivation of hydrocarbon reactions over Pt catalysts

The reactions of cyclohexane (6.7 kPa) andn-hexane (13.3 kPa) in H2 (450 kPa) were studied on platinum-rhenium model catalysts in the range 570–740 K. The catalysts were prepared by depositing rhenium on a platinum foil or platinum on a rhenium foil. The catalyst total area was 0.5–1.0 cm2. The surfaces were pre-sulfided before reaction and thiophene added to the feed to maintain the surface sulfided under reaction conditions. Sulfur binds with rhenium forming a catalytically inactive rhenium-sulfur compound. As the concentration of rhenium-sulfur on the surface is increased and the platinum ensembles become smaller, only dehydro-genation-hydrogenation activity is observed. However, the catalyst becomes more resistant to deactivation.

Electrolytic preparation of actinide filaments for laser resonance ionization spectroscopy

For the determination of trace amounts of actinide elements by resonance ionization mass spectroscopy, atomic beams of these elements are produced by evaporation from rhenium substrates. The actinides are deposited by electrolysis as hydroxides in a 2 mm spot on a rhenium foil and covered electrolytically with a thin layer of rhenium or platinum. During heating of such a sandwich reduction occurs to the metallic state while diffusing through the overplated layers and the actinides are evaporated as atoms from the surface. With lead-doped platinum, efficient release is observed already at 1700°C in contrast to rhenium where 2100°C is required and a higher background is produced.

Collisionally-activated dissociation in hyperthermal surface ionization of cholesterol

Cholesterol in a hydrogen-seeded supersonic molecular beam was scattered from a continuously oxidized rhenium foil. The hyperthermal surface scattering exhibited efficient molecular ionization with a controlled amount of molecular ion dissociation. At 5.3 eV incident molecular kinetic energy the hyperthermal surface ionization mass spectrum was dominated by the parent molecular ion. Upon the increase of the molecular kinetic energy, a gradual increase in the degree of ion dissociation was observed. At 22eV incident kinetic energy the parent ion was completely dissociated and the mass spectrum was dominated by an extensive consecutive fragmentation. An efficient kinetic-vibrational energy transfer was observed, and it is extimated to be over 18% of the available incident kinetic energy. The implication for surface collisionally-activated dissociation of polyatomic ions is discussed. Rhenium oxide is suggested as an optimal surface for this purpose, as well as for the hyperthermal surface ionization of neutral species.

Work function measurements on rhenium foils in a directed cesium flux: Thermionic converter applications

The effective electron work function was measured on polycrystalline Re surfaces with a continuous Cs flux directed on the surface. Surface temperatures of 400–1600 K were used, and work functions as low as 1.0±0.1 eV were found between 400 and 700 K. The Cs flux density corresponded to a pressure less than 10 -3 mbar. Similar work functions were usually found for both the front side of the sample (12.5 μm thick 99.99% Re foil) and for the back, which was not exposed to any Cs flux from the gas phase or the beam. No ionized gas phase outside the sample contributed to the large electron currents measured. Both bulk and surface diffusion processes transported Cs to the back of the sample. The low work functions are attributed to the existence of oxygen buried in the topmost layers of the metal, thus giving a low work function with only a small possibility of removal by Cs attack. Any great influence of rhenium oxides or cesium oxides is ruled out by the experimental situation. Re surfaces with subsurface oxygen appear to be of great interest as collectors in thermionic energy converters.

Fabrication of slots in a cathode front surface using a pinhole ion lens

The feasibility of fabricating a thermionic cathode with controlled pore geometry via projection ion lithography is demonstrated in this paper. The advantages of such cathodes over the porous-plug type currently in use are described, followed by a brief description of the pinhole ion lens and its general applications. Examples of controlled pore images produced in substrates and refractory metal foils using different variations of the pinhold ion lens technique are given. The technique used for etching slots is described, and slot arrays etched in rhenium foil, tungsten foil, and in the front surface of a controlled pore dispenser cathode are examined. The slots produced ranged from 13 μm wide by 580 μm long in rhenium to 6 μm wide by 64 μm long in tungsten.

Reactor thermal neutron flux monitoring with rhenium foils at high temperature in on-line isotope separation

The feasibility of applying rhenium as a thermal neutron flux monitor at high temperature in on-line isotope separation was investigated experimentally. Measurements of the integrated flux take into consideration the fluctuations in the thermal neutron flux during the irradiation of the ion source. The integrated thermal neutron flux was calculated from the absolute activity of 188Re and measured with a calibrated Ge(Li) detector. Good results were obtained at temperature in the region of 1800°C.