Abstract
Diopside is a common natural pyroxene that is rarely found in a pure state, since magnesium is often partially substituted by iron, and other elements (sodium and aluminum) are often present. This pyroxene, along with feldspars and olivines, is common in concrete. As the prospective license renewal of light water reactors to 80 years of operation has raised concerns on the effects of radiation in the concrete biological shield surrounding the reactors, mineral nanoparticles can be valuable to perform amorphization studies to inform predictive models of mechanical properties of irradiated concrete. The synthesis of diopside nanoparticles was achieved in this study using a reverse-micelle sol-gel method employing TEOS, calcium chloride and Mg(MeO)2 in a methanol/toluene solution. Tert-butylamine and water were used as hydrolysis agents, and dodecylamine as a surfactant. The resulting amorphous precursor was centrifuged to remove organics and fired at 800 °C. Additional reaction with hydrogen peroxide was used to remove amine remnants. TEM and SEM examinations revealed a product comprised of 50–100 nm diameter nanoparticles. XRD indicated phase pure diopside and BET indicated a surface area of 63.5 m2/g before peroxide treatment, which at a bulk density of 3.4 g/cm3 is equivalent to particles with diameter of 28 nm.
Highlights
Diopside is a common natural pyroxene that is rarely found in a pure state, since magnesium is often partially substituted by iron, and other elements are often present
This paper describes a relatively simple method for the synthesis of such materials
The alkoxides, TEOS and Mg(MeO)[2] were dissolved in toluene, while calcium nitrate was dissolved in methanol
Summary
Diopside is a common natural pyroxene that is rarely found in a pure state, since magnesium is often partially substituted by iron, and other elements (sodium and aluminum) are often present. The analysis of nanoparticles and other surfaces has shown that the surface properties may vary significantly from those ascribed to the bulk[9,10,11,12,13,14] No studies of these effects in pyroxenes are available. The underlying cause of this loss in mechanical properties is RIVE (radiation induced volumetric expansion)[15] Minerals such as quartz, feldspars, olivines and pyroxenes are commonly found in concrete aggregates. Data on volumetric expansion with dose for a variety of minerals is, critically needed in assessing reactor safety Amorphization is another process known to occur during irradiation that affects the structural properties of minerals. For instance, studied the critical amorphization ion doses of several silicate minerals by obtaining diffraction patterns of samples bombarded with 1.5 MeV Kr+ 16 This technique has been shown to be successful. Harbsmeier and Bolse[17] found that complete amorphization of α-quartz occurred at a dpa (displacement per atom) of 0.04, whereas Eby’s data suggested a much larger dpa of 0.11 was required
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