Curium oxide

Curium, oxidation number, 414 Cyclohexane, properties, 341 Cyclopentane, 340 Cyclopentene, 342... 

Two other methods have been used successfully to prepare very pure Cm metal. A rather unique one is thermal decomposition of the intermetallic compound PtjCm produced by hydrogen reduction of curium oxide in the presence of Pt (36, 82). The second method, the method of choice for gram-scale preparations of very pure Cm metal, involves reduction of curium oxide with Th metal (8, 83) in an apparatus... 

In research al the Institute or Radiochemistry. Karlsruhe, West Germany during Ihe early 1970s. investigators prepared alloys of Curium with iridium, palladium, plalinum. and rhodium. These alloys were prepared by hydrogen reduction of the curium oxide or fluoride in the presence of finely divided noble metals. The reaction is called a coupled reaction because the reduction of the metal oxide can be done in the presence of noble metals. The hydrogen must be extremely pure, w ith an oxygen content of less than 10 -s Inrr. 

A number of compounds of curium have been produced, including two forms of curium oxide (Cm203 and Cm02), two forms of curium fluoride (CmF3 and CmF4), curium chloride (CmCl3), curium bromide (CmBr3), and curium hydroxide (Cm(OH)3). 

Starting from prepurified oxides and using lanthanum metal as reductant, volatile Am, Cf or Es have been isolated and purified by repeated distillation or sublimation. Thorium was used successfully as reductant for actinium and curium oxides (2) ... 

The vaporization behavior for Cm sesquioxide has been reported (Smith and Peterson 1970). Mass-spectrometric data were not obtained in this study and the species were assigned based only on the systematics. The researchers believed these data support the congruent vaporization of Cm203 to yield CmO(g) and 0(g). An enthalpy of vaporization of 1795kJmol at OK was derived. Curium oxides with O/M ratios higher than 1.5 are not stable above 900°C (Cm02 decomposes above 400°C), and therefore the vaporization processes of oxides having O/M ratios above 1.5 cannot be measured experimentally. 

Heating mixtures of curium oxide and alumina affords CmA103, which gives either a rhombohedral or cubic product depending upon the quenching conditions [102]. The rhombohedral phase transforms to the cubic phase at room temperature. BaCm03 has also been reported [103,172]. 

A fused salt-molten metal process has also been examined for separating californium [36, 37]. In principle, it may also be possible to reduce actinide oxides with thorium metal and distill away the more volatile californium metal (see Section 11.6.1). The separation of californium oxide from curium oxide using a vacuum sublimation procedure has also been reported [38]. 

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