Nagelschmidtite as a candidate host phase for actinides, rare earth and different waste elements

MRS Advances ◽  
2017 ◽  
Vol 3 (20) ◽  
pp. 1073-1083
Author(s):  
Sergey V. Stefanovsky ◽  
Olga I. Stefanovsky ◽  
Ivan L. Prusakov
Keyword(s):  
Continuous Solid Solution ◽  
Induction Melting ◽  
Average Chemical Composition ◽  
Temperature Synthesis ◽  
Waste Forms ◽  
Phase Average ◽  
High Temperature Synthesis ◽  
Metallurgical Slags ◽  
Geological Formations ◽  
Nuclear Waste Forms

AbstractNagelschmidtite, Ca7P2Si2O16, is an end-member of continuous solid solution Ca2SiO4 – Ca3(PO4)2⋅2Ca2SiO4 within the pseudo-binary system Ca3(PO4)2 – Ca2SiO4 (whitlockite – larnite). This phase is capable to wide isomorphic exchanges in Ca, P and Si sites: Ca2+ = Sr2+; Ca2+ = Eu2+; Ca2+ + P5+ = (RE,An)3+ + Si4+, 2Ca2+ = Na+ + (RE,An)3+; 2Ca2+ = An4+ + ☐; Ca2+ + Si4+ = (RE,An)3+ + (Al,Fe)3+; Ca2+ + Si4+ = Na+ + P5+; 2Ca2+ = Na+ + (Al,Fe)3+; Ca2+ + P5+ = Na+ + S6+. It was found in metallurgical slags and geological formations. We revealed nagelschmidtite-type phase in vitrified phosphorus-bearing radioactive incinerator slags. The materials were glass-crystalline and contained nano-sized nagelschmidtite crystals distributed in vitreous matrix phase. Average chemical composition of the largest (few microns) crystals was recalculated to formula Na1.21K1.05Ca2.22Al2.02Fe0.46Si2.69P1.26U0.08O15.76. Significant oxygen misbalance suggests higher than U(IV) oxidation state for uranium – U(V) or U(VI). Capability of nagelschmidtite to be crystallized from melt makes it promising phase for actinides, rare earths and some other fission and corrosion products at using a melting route to nuclear waste forms including cold crucible induction melting and self-propagating high-temperature synthesis.

scholarly journals The Directions of Creation of Unique Technologies in Medicine on the Basis of New Generation of Biocompatible Materials and Implants With Shape Memory

2017 ◽  
Vol 2 (1) ◽  
pp. 1 ◽  
Author(s):  
V.E. Gunther
Keyword(s):  
High Temperature ◽  
Powder Metallurgy ◽  
Shape Memory ◽  
Biocompatible Materials ◽  
Induction Melting ◽  
Temperature Synthesis ◽  
New Class ◽  
High Temperature Synthesis ◽  
Melting Technique ◽  
New Generation

The article describes the main directions of creation of unique technologies in medicine on the basis of new generation of biocompatible materials and implants with shape memory effect (SME). Physical and biological fundamentals and principles of creating a new class of biocompatible superelastic TiNi-based materials were drafted. Manufacturing technique of TiNi-based materials with using the induction melting technique, self-extending high-temperature synthesis and powder metallurgy with a certain complex of properties for various fields of medicine have been developed.

scholarly journals Rapid Immobilization of Simulated Radioactive Soil Waste Using Self-Propagating Synthesized Gd2Ti2O7 Pyrochlore Matrix

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1163 ◽  
Author(s):  
Jiali Xue ◽  
Kuibao Zhang ◽  
Zongsheng He ◽  
Wenwen Zhao ◽  
Weiwei Li ◽  
...  
Keyword(s):  
Phase Composition ◽  
High Temperature ◽  
Contaminated Soil ◽  
Chemical Durability ◽  
Leaching Rate ◽  
Rapid Synthesis ◽  
Temperature Synthesis ◽  
Main Work ◽  
Waste Forms ◽  
High Temperature Synthesis

A rapid and effective method is necessary in the disposal of severely radioactive contaminated soil waste. Simulated Ce-bearing radioactive soil waste was immobilized by self-propagating high-temperature synthesis (SHS) within 5 min in this study. The main work includes the rapid synthesis of soil waste forms, the analysis of phase composition, microstructure and chemical durability. These results show that the simulated nuclide Ce was successfully immobilized into the pyrochlore-rich waste matrice, whose main phases are SiO2, pyrochlore (Gd2Ti2O7) and Cu. The normalized leaching rates of Si and Na on the 42nd day are 1.86 × 10−3 and 1.63 × 10−2 g·m−2·d−1, respectively. And the normalized leaching rate of Ce also remains at low level (10−5–10−6 g·m−2·d−1) within 42 days.

Self-Propagating High-Temperature Synthesis of Simulated 90SrO-Contained Radioactive Graphite in N2 Atmosphere

2014 ◽  
Vol 525 ◽  
pp. 45-52 ◽  
Author(s):  
Xi Rui Lu ◽  
Si Jin Su ◽  
Meng Jun Chen
Keyword(s):  
Titanium Dioxide ◽  
High Temperature ◽  
Titanium Carbide ◽  
Exothermic Reaction ◽  
The Self ◽  
Cubic Phase ◽  
Temperature Synthesis ◽  
Radioactive Graphite ◽  
Waste Forms ◽  
High Temperature Synthesis

In order to evaluate the performance of the self-propagating high-temperature synthesis (SHS) to treat 90SrO-contained radioactive graphite in N2 atmosphere, waste forms were prepared with the self-developed SHS reactor according to the waste forms formulation designed with a solid-soluted content of 010 wt% (calibrated in mass, hereinafter the same). The waste forms were made with the exothermic reaction (3C + 4Al + 3TiO2 = 2Al2O3 + 3TiC + Q), where, 88SrO (a stable Sr isotope)-containing 88SrO was used to simulate 90SrO. And the raw materials for the waste forms were the powdery materials of graphite (C), aluminum (Al) and titanium dioxide (TiO2). Then, X-ray diffractometer (XRD) and scanning electron microscope (SEM) were used to test and analyze the phase composition and morphology of the prepared waste forms. According to the results in dealing with the treatment with the given exothermic reaction of the 90SrOcontaining radioactive graphite in N2 atmosphere, the SrO solid solubility could be up to 8 wt%. Besides, with a SrO content of 0~2 wt%, the major composition of the waste forms was including: alumina (Al2O3) in diamond scheme, titanium carbide (TiC) in cubic phase, graphite (C), anatase titanium dioxide (TiO2) and aluminum nitride (AlN) in cubic phase. Comparatively, with a SrO content of 3~8 wt%%, the major composition of the waste forms was including: alumina (Al2O3) in diamond scheme, titanium carbide (TiC) in cubic phase, graphite (C), anatase titanium dioxide (TiO2), aluminum nitride (AlN) in cubic phase and rhomboid aluminum titanate (Al2TiO5). Furthermore, diffractive peaks of unidentified phase occurred at 2θ = 7.7°, 15.6°, 19.8° and 24.1° position, whose intensities were increased with the increasing additional SrO content. The grain sizes of the prepared waste forms are mainly within 515μm, majorly exist in pieces.

Hardening of metal surface via self-propagating high-temperature synthesis in thin films

2007 ◽  
Vol 43 (4) ◽  
pp. 239-242
Author(s):  
S. Kh. Suleimanov ◽  
O. A. Dudko ◽  
V. G. Dyskin ◽  
Z. S. Settarova ◽  
M. U. Dzhanklych
Keyword(s):  
Thin Films ◽  
High Temperature ◽  
Metal Surface ◽  
Temperature Synthesis ◽  
High Temperature Synthesis

Effect of Additives on the Characteristics of Amorphous Nano Boron Powder Fabricated by Self-Propagating High Temperature Synthesis

2015 ◽  
Vol 25 (12) ◽  
pp. 659-665
Author(s):  
Sin Hyong Joo ◽  
Hayk H. Nersisyan ◽  
Tae Hyuk Lee ◽  
Young Hee Cho ◽  
Hong Moule Kim ◽  
...  
Keyword(s):  
High Temperature ◽  
Temperature Synthesis ◽  
Boron Powder ◽  
Effect Of Additives ◽  
High Temperature Synthesis
Sign in / Sign up

Export Citation Format

Share Document