The Thermal Decomposition of Three Magnetic Acetates at Their Autogenic Pressure Yields Different Products. Why?

Abstract

We report on the one‐stage, reproducible, solvent‐free, competent and straightforward approach for the synthesis of fullerene‐like Ni@C, Co@C, and Fe3O4@C core‐shell nanostructures that can be scaled up. The single precursor reactions of low cost acetates of Fe, Co and Ni are separately conducted at a relatively low temperature (700 °C) in a closed Swagelok reactor, as compared to other methods for the formation of graphitic layers. It is worth mentioning that although identical reaction parameters are employed, using the three acetate precursors, the graphitic carbon is coated on nanosized metallic Ni and Co cores, while Fe tends to form Fe3O4, maintaining the same core‐shell morphology. The systematic morphological, compositional, structural characterization and the room temperature magnetic susceptibility measurements of the as‐made particles are carried out on a vibrating sample magnetometer. The plausible mechanism is based on the comparison between the dissociation products of three acetate precursors, their obtained experimental data, and calculations on the enthalpy and free energy changes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

One‐Step Solvent‐Free Synthesis and Characterization of Zn1−xMnxSe@C Nanorods and Nanowires

“…According to the previous report, all the products of the dissociation reaction, in a closed Swagelok reaction, float in the gas phase and solidify right after their formation. [30] The dissociation of acetates involves the following steps: [31] MðCH 3 COOÞ 2 Á xH 2 O ! MðCH 3 COOÞ 2 þ xH 2 O ðM ¼ Zn; MnÞ (1)…”

“…M þ CO 2 ðdoes not occurÞ (6) The metal carbonate, which is a short-lived intermediate, immediately decarboxylates to give a metal oxide at 350 8C. [31] However, the carbon monoxide and carbon, formed from Equations 3 and 4, respectively, cannot reduce the metal oxides as the standard reduction potential values at 25 8C for Zn and Mn are À0.76 and À1.18 V, respectively. [32] Hence, the reactions according to Equation 6 do not occur and (Zn 1Àx Mn x ) À O is formed according to Equation 5.…”

Physical mixing of metal acetates: a simple, scalable method to produce active chloride free bimetallic catalysts

“…17 The process of thermal decomposition of metal acetates, required in the production of catalysts, has been shown to be complex and quite sensitive to heat treatment conditions. [18][19][20] Auto-reduction during heat treatment under inert atmospheres, combined with the potential of metal acetates to sublime, 17 is considered to control the size of metal particles and their interaction with the support.…”

NiO<sub>x</sub> Nanoparticle Synthesis by Chemical Vapor Deposition from Nickel Acetylacetonate

“…The precursor concentration was controlled both by the flow rate through the saturator and by the saturator temperature (T S ). The partial pressure of the precursor vapor was calculated on the basis of the experimental data of Götze et al [18]…”