Physikalische und chemische Eigenschaften des Rheniums

Agte, C.; Alterthum, H.; Becker, Karl‐Friedrich; Heyne, Gerton; Moers, K.

doi:10.1002/zaac.19311960116

Cited by 50 publications

(6 citation statements)

References 18 publications

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“…The Tc K edge and Re L 2 edge EXAFS spectra of these samples are shown in Figure and the fitting results are in the Supporting Information. The distances determined from fitting the EXAFS are in good agreement with the hcp structure of the metals. , Both samples are actually Tc:Re alloys: sample II-216 has a Tc:Re ratio of 6:1 and sample II-214 has a ratio of 1:3. Because II-216 contains mainly Tc in the metallic phase, it is referred to as Tc(0), and II-214 is referred to as Tc/Re.…”

Section: Resultssupporting

confidence: 61%

Dissimilar Behavior of Technetium and Rhenium in Borosilicate Waste Glass as Determined by X-ray Absorption Spectroscopy

et al. 2007

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ABSTRACT. Technetium-99 is an abundant, long-lived ( 1/2 = 213,000 yr) fission product that creates challenges for the safe, long-term disposal of nuclear waste. While 99 Tc receives attention largely due to its high environmental mobility, it also causes problems during its incorporation into nuclear waste glass due to the volatility of Tc(VII) compounds. This volatility decreases the amount of 99 Tc stabilized in the waste glass and causes contamination of the waste glass melter and off-gas system. The approach to decrease the volatility of 99 Tc that has received the most attention is reduction of the volatile Tc(VII) species to less volatile Tc(IV) species in the glass melt. On engineering scale experiments, rhenium is often used as a non-radioactive surrogate for 99Tc to avoid the radioactive contamination problems caused by volatile 99 Tc compounds.However, Re(VII) is more stable towards reduction than Tc(VII), so more reducing conditions would be required in the glass melt to produce Re(IV). To better understand the redox behavior of Tc and Re in nuclear waste glass, a series of glasses were prepared under different redox conditions. The speciation of Tc and Re in the resulting glasses was determined by X-ray absorption fine structure spectroscopy. Surprisingly, Re and Tc do not behave similarly in the glass melt. Although Tc(0), Tc(IV), and Tc(VII) were observed in these samples, only Re(0) and Re(VII) were found. In no case was Re(IV) (or Re(VI)) observed.

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Section: Resultssupporting

confidence: 61%

Dissimilar Behavior of Technetium and Rhenium in Borosilicate Waste Glass as Determined by X-ray Absorption Spectroscopy

et al. 2007

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“…Comparison of the gravimetric data with observed metal-recession indicates that with both alloys there are two concurrent processes taking place: (i) oxidation of Cr to Cr203, and (ii) oxidation of Re to ReO3 or Re2OT, both of which are volatile at the oxidation temperature (15)(16)(17). Since the Cr-32 a/o Re alloy showed weight gains in the gravimetric experiments at 1200~ and above, it appears that in this temperature range the external Cr203 scale acts as a barrier to further oxidation, and hence linear kinetics do not obtain.…”

Section: Discussionmentioning

confidence: 95%

“…The oxidation of Re has been studied by several investigators (15)(16)(17). Above about 600~ linear rates of weight loss are observed due to the formation of volatile Re oxides, probably ReO3 or Re207 (17).…”

mentioning

confidence: 99%

The High-Temperature Oxidation of Ductile Cr-Re Alloys

Tedmon

1966

J. Electrochem. Soc.

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The high-temperature oxidation behavior of ductile Cr-Re alloys containing 32 and 44 a/o (atomic per cent) Re has been investigated using thermogravimetric, metallographic, electron microbeam probe, and x-ray analytical techniques. The oxidation reactions taking place include the formation of a Cr203 external scale, a subscale, and volatile Re oxides. The Cr203 scale which forms on the Cr-32 a/o Re alloy is an effective barrier to loss of Re; on the Cr-44 a/o Re alloy, the Cr203 scale is quite porous, and Re loss as volatile oxide ensues, giving rise to linear kinetics. Air-oxidized samples showed essentially the same kinetics as samples exposed to oxygen; Cr2N did not form.Cr-Re alloys with Re concentrations near the bcc a-phase solubility limit possess good ductility and high strength (1-3). Since the use of Cr as a structural material has been limited historically by its lack of ductility at low temperature (T<300~ (4-7), the discovery of the Re ductilizing effect has aroused increased interest in ductile Cr-base alloys. Although there is considerable interest in potential applications of Cr-Re alloys at elevated temperatures, an understanding of their oxidation behavior has been lacking.Over the temperature range of 700~176 unalloyed Cr oxidizes with parabolic kinetics (8-11). The rate is primarily controlled by Cr +3 cation diffusion (8, 12, 13) although other factors such as surface preparation (ll), oxide blistering (8, ll) and oxide evaporation (8, ll, 14) can alter the kinetics significantly. Caplan et al. have suggested that anion diffusion could also affect the kinetics (11).The oxidation of Re has been studied by several investigators (15)(16)(17). Above about 600~ linear rates of weight loss are observed due to the formation of volatile Re oxides, probably ReO3 or Re207 (17).The objectives of this investigation were to determine the oxidation behavior of ductile Cr-Re alloys and to identify the factors controlling the kinetics. Experimental ProcedureSample preparation.--The melt stock used for the alloys was iodide Cr (99.99%) and Re powder (Chase Brass, 99.99%). The Re powder was vacuum sintered in an electron-beam furnace prior to melting in order to reduce surface oxide and surface area.The ductility of Cr-Re alloys increases with increasing Re content (3, 18), including Cr supersaturated with Re. Two compositions were studied, viz., Cr-32 a/o Re and Cr-44 a/o Re. Both alloys were prepared by nonconsumable electrode arc-melting under purified argon. Chemical analyses of the alloys are presented in Table I. As prepared, both alloys were single phase, ~-bcc structures. The solubility limit of Re in Cr, below about 1400~ is 36 a/o; above this temperature the solubility increases to 50 a/o at 2280~ (19). The Cr-44 a/o Re alloy, as cast, was supersaturated with respect to Re. Metallographic examination and electron microbeam probe scans showed the alloys to be homogeneous. During oxidation runs at ll00~ and above, the Cr-44 a/o Re alloy transformed to a two-phase ~+~ structure.Kinetic measurements.--S...

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“…While this measurement is significant and highlights that the E‐CNL system can achieve exceptionally high temperatures, more work is required. The next series of experiments to be conducted will be to measure the melting points of a series of di‐borides: TiB 2 (Tm = ∼3193 K 22 ) ZrB 2 (Tm = ∼3323 K 22 ), NbB 2 (Tm = ∼3323 K 22 ), HfB 2 (Tm = ∼3513 K 22 ), TaB 2 (Tm = ∼3473 K 22 , carbides: TiC (Tm = ∼3340 K 20 ), ZrC (Tm = ∼3784 K 102 ), NbC (Tm = ∼3886 K 20 ), HfC (∼4201K 20 ) TaC (Tm = ∼4168 K 20 ) and the highest estimated melting point materials Ta 0.8 Hf 0.2 C (Tm = ∼4178 K 103 ) and Hf(C,N) (Tm = ∼4135 K 104 ). These experiments will be challenging, exciting, and impactful for three key reasons: (1) the melting points of these materials are not well established as there are only a few measurements in the literature, (2) the emissivity of these materials are not well characterized with evidence that some of these materials exhibit changes in NSE (0.29–0.4 in ZrB 2

\lambda \; = \;0.655\;\mu {\mathrm{m}}

) 105 at high temperature, and (3) their melting points are all high, with some approaching the upper limit measured on HfO 2 (4250 ± 34 K).…”

Section: Introductionmentioning

confidence: 99%

Environmental conical nozzle levitator equipped with dual wavelength lasers

Thorpe,

Li,

Weber

et al. 2023

J Am Ceram Soc.

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The environmental conical nozzle levitator (E‐CNL) with dual‐wavelength lasers is an extreme environment materials characterization system that was designed to investigate ultra‐high‐temperature materials: refractory metals, oxides, carbides, and borides above 3000 K in a controlled atmosphere. This article details the characterizations using this system to establish its high‐temperature capabilities and to outline ongoing work on materials under extreme conditions. The system has been used to measure the melting point of several oxide materials (TiO2, Tm = 2091 ± 3 K; Al2O3, Tm = 2310 3 K; ZrO2, Tm = 2984 31 K; and HfO2, Tm = 3199 ± 45 K) and several air‐sensitive refractory metals (Ni, Tm = 1740 K; Ti, Tm = 1983 K; Nb, Tm = 2701 K; and Ta, Tm = 3368 K—note: mean ± standard deviation) during levitation which matched literature values within 0.17–2.43 % demonstrating high accuracy and precision. This containerless measurement approach is critical for probing properties without container‐derived contamination, and dual‐wavelength laser heating is essential to heat both relatively poor electrical conductors (some refractory metals and carbides) and insulators (oxides). The highest temperature achieved utilizing both lasers in these experiments was ∼4250 ± 34 K on a 76.6 mg, molten HfO2 sample using a normal spectral emissivity of 0.91. Stable levitation was demonstrated on spherical samples (yttria‐stabilized zirconia) while adjusting levitation gas composition from pure oxygen to pure argon, verifying atmospheric control up to 3173 K on solid or molten samples. These successes demonstrate the viability of in situ high‐temperature environmentally controlled studies potentially up to 4000 K on all classes of ultra‐high‐temperature materials in one system. These measurements highlight the E‐CNL system will be essential for the development of next‐generation ultra‐high‐temperature materials for hypersonic platforms, nuclear fission and fusion, and space exploration.

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Physikalische und chemische Eigenschaften des Rheniums

Cited by 50 publications

References 18 publications

Dissimilar Behavior of Technetium and Rhenium in Borosilicate Waste Glass as Determined by X-ray Absorption Spectroscopy

Dissimilar Behavior of Technetium and Rhenium in Borosilicate Waste Glass as Determined by X-ray Absorption Spectroscopy

The High-Temperature Oxidation of Ductile Cr-Re Alloys

Environmental conical nozzle levitator equipped with dual wavelength lasers

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