Pyrite Formation via Kinetic Intermediates through Low-Temperature Solid-State Metathesis

Abstract

The preparation of materials with limited phase stabilities yet high kinetic activation barriers is challenging. Knowledge of their possible formation pathways aids in addressing these challenges. Metathesis reactions present an approach to circumvent these barriers; however, solid-state metathesis reactions are often too rapid from extensive self-heating to understand the reaction. The stoichiometric reaction of MCl2 salts (M = Mn, Fe, Co, Ni, Cu, Zn) with Na2S2 enables the formation of pyrite (FeS2), CoS2, and NiS2 at low temperatures (250-350 °C). Na2S2 has the same polyanionic dimer as found in the pyrite structure, which would suggest the possibility of a facile ion-exchange reaction. However, from high-resolution synchrotron X-ray diffraction and differential scanning calorimetry, the energetic driving force does not appear to result solely from NaCl formation but also from formation of intermediate and pyrite phases. It is apparent that the reaction proceeds through polyanionic disproportionation and formation of a low-density alkali-rich intermediate, followed by anionic comproportionation and atomic rearrangement into the pyrite phase. These results have profound implications for the use of low-temperature metathesis in achieving materials by design.

Protocols for High Temperature Assisted-Microwave Preparation of Inorganic Compounds

“…[56][57][58] Lower temperature (500 K to 650 K) metathesis reactions have allowed some pyrites to synthesized in just days by circumventing kinetic barriers. 59,60 Butala et al demonstrated microwave preparation of Fe 1−x Co x S 2 and CuTi 2 S 4 , accelerating reaction times to less than 40 minutes. 61 The microwave electromagnetic field interacts strongly with the transition metal, selectively heating the metal powder and allowing the reaction to occur rapidly at metal sites before significant sublimation of the chalcogen.…”

Nanocrystalline Pyrite for Photovoltaic Applications

“…Martinolich et al . reported the salt‐exchange metathesis reaction approach for the synthesis of high purity pyrite at low temperature 350 °C through intermediate pyrite phases.…”

TBC1D21 Potentially Interacts with and Regulates Rap1 during Murine Spermatogenesis

“…Several GEFs (e.g., EPAC, C3G, PDZ-GEFs, CalDAGs, and RapGEF6) have been indicated as activating Rap1 for GTP forms in different cells [ 12 , 27 , 28 , 29 , 30 , 31 ]. Two of them, EPAC and RapGEF6, are involved in male germ cells [ 13 , 30 ]. EPAC (exchange protein directly activated by cAMP) is colocalized with Rap1 within murine spermatocytes and round spermatids.…”

“…Knockout of another GEF, RapGEF6, results in male infertility, and accounts for reduced testis size as well as reduced sperm count and motility. Moreover, the knockout also produces high percentages of morphologically abnormal sperm [ 30 ]. Several GAPs are involved in the inactivation of Rap1 in non-germ cell lines (e.g., Rap1-GAP1, Rap1-GAP2, Spa1, and SPAR1,2,3) [ 27 ].…”