Volatility Studies of Lanthanide Hexafluoroacetylacetone Chelates

Journal Article · Fri Jul 01 04:00:00 UTC 2016 · Transactions of the American Nuclear Society

OSTI ID:23042623

Shahbazi, Shayan ^[1]; Auxier, II, John D.; Hall, Howard L. ^[2]

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1. Department of Nuclear Engineering, University of Tennessee, Knoxville 37996 (United States)
2. Department of Nuclear Engineering, Institute for Nuclear Security, Radiochemistry Center of Excellence, University of Tennessee, 1640 Cumberland Avenue, Knoxville 37966 (United States)

Nuclear forensics has become very important to the field of nuclear security, where there is considerable interest in developing rapid separations of radionuclides and isotopes. Although prevention and detection form the foundation of nuclear security science, in the unfortunate event of detonation of a nuclear device, the fallout debris can be analyzed for signature isotopes that may provide evidence on the origin and type of nuclear materials. This is of considerable political importance to many governing bodies and this information is desired in a timely manner. One method of analysis is the rapid gas phase separation of rare earth metals from other components of the debris via isothermal thermochromatography. Lanthanides cover a portion of the fission product curve with varying yields dependent on a number of variables (e.g. neutron energy, fissile parent, etc), motivating the chromatographic separation of these elements. In previous work, 1,1,1,5,5,5 - hexafluoroacetylacetone (hfac) has been shown to produce volatile complexes with lanthanides. Thermochromatography is a gas phase separation method that utilizes temperature gradients on a column to vary adsorption location or constant column temperatures to vary retention time. The adsorption time of a compound on a column, i.e. retention time, is dependent on the thermodynamics, most notably the adsorption enthalpy. Studies of heavy metals have generated empirical correlations between adsorption enthalpy on a quartz column and sublimation enthalpy of the solid material. Thermogravimetric analysis (TGA) is useful in the characterization of the thermodynamics of materials, especially the sublimation enthalpy. Many methods analyze weight loss curves as a function of a constant heating rate. Another method introduced by Ashcroft analyzes weight loss curves over isothermal heating regions. Work presented here focuses on the determination of the sublimation enthalpies of thirteen lanthanide hfac complexes via the latter method. Additionally, there is investigation into the degradation of the compound via constant heating TGA up to higher temperatures. This provides information on the onset and end-set temperatures of degradation stages, as well as the peak temperature at which total sublimation occurs. (authors)

• OSTI ID: 23042623
• Journal Information: Transactions of the American Nuclear Society, Journal Name: Transactions of the American Nuclear Society Vol. 115; ISSN 0003-018X
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION
ADSORPTION
CHELATES
FISSION PRODUCTS
HEATING RATE
HEAVY METALS
NEUTRONS
NUCLEAR FORENSICS
RADIOISOTOPES
RARE EARTHS
SUBLIMATION HEAT
TEMPERATURE GRADIENTS
THERMAL GRAVIMETRIC ANALYSIS
THERMOCHROMATOGRAPHY
THERMODYNAMICS
VOLATILITY