Rhenium dioxide

Figure 8. TEM picture of a nanostructured rhenium dioxide synthesized with hexadecylamine at a surfactant...

X-ray absorption spectroscopy has proved the presence of rhenium dioxide within this nanostructure [12]. Extraction of the surfactant with various solvents remained inefficient since either the surfactant persists within the composite or the nanostructure is lost. Calcination at mild temperatures as low as 300-350°C in nitrogen atmosphere leads to a mass loss under these pyrolytic conditions of about 50% with only little loss of the nanostructure. Similar results are obtained when the composite is oxidatively treated in an oxygen plasma for not more than ten minutes. Physisorption measurements on the calcined or plasma treated samples show only very small surface areas, which cannot be assigned to a mesoporous structure. Right now we believe that residual carbon may introduce some pore blocking effects within the nanostructure preventing good access of the inner pore surfaces. 

We could show that the modification of transition metal alkoxides is a versatile tool to adjust the reactivity of precursors for the needs in lyotropic crystalline templating processes. In case of high surfactant concentrations where the liquid crystalline template is formed prior to the addition of the precursor the use of a modifier may become unnecessary. The synthesis of nanostructured rhenium dioxide and the utilization of MTO as precursor for this purpose clearly shows that in some cases the use of unusual specialized compounds is imperative. First promising results in the synthesis of nanostructured chromium oxide surfactant composites have been displayed although hydrolysis of the precursor seems to be still uncompleted within the nanostructure. The possibility of tailoring the d-values in a desired way besides the synthesis of certain particle morphologies encourages for further work in the future. 

Single crystals of tungsten and rhenium dioxides are grown by a procedure that is analogous to that previously described for osmium dioxide, except that iodine is used as the transport agent. The reaction is presumed to involve an oxyiodide and to be of the type ... 

Two crystallographic forms of rhenium dioxide are known. When synthesized below 300°, the structural modification (a) is... 

Size of Platinum, Rhenium Dioxide, and Gold Particles... 

Rhenium dioxide, Re02-aq, black, is obtained by reducing Re04 (rapidly if hot and concentrated) in 12-M OH by N2H4 from N2H5CI. 

Single crystals of tungsten and rhenium dioxides are grown by a procedure that is analogous to that previously described for osmium dioxide, except... 

Two crystallographic forms of rhenium dioxide are known. When synthesized below 300°, the structural modification (a) is isostructural with tungsten dioxide. Above 300°, this modification transforms irreversibly to an orthorhombic form (P), and when initial synthesis is carried out at temperatures greater than 300°, the -modification is invariably recovered. Therefore, the crystals grown by the process described above are -rhenium dioxide and have an orthorhombic unit cell with a = 4.809 A, = 5.643 A, and Co = 4.601 A. The crystals are black, possess a columnar habit, are about... 

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