ALBERT

Description: 〈span〉〈div〉Abstract〈/div〉We provide an experimental confirmation of the suggestion, based on thermodynamic simulations and extrapolations (〈a href="https://pubs.geoscienceworld.org/ammin#B30"〉Zhong et al. 2015〈/a〉), that Zn is transported in the form of chloride complexes in most acidic, shallow hydrothermal systems; while bisulfide complexes become increasingly important in deep, pH neutral to basic hydrothermal systems. We used in situ X-ray absorption spectroscopy (XAS) diamond-anvil cell experiments to determine Zn(II) speciation in a 1 m NaHS + 0.2 m HCl solution in contact with sphalerite. XANES data indicate that Zn coordinates to oxy/hydroxyl/chloride ligands from room temperature up to and including 200 °C, and then at higher temperatures (≥300 °C) and pressures (〉2 kbar) it changes to complexing with sulfur. Our data confirm that bisulfide complexes become increasingly important in neutral-alkaline solutions at high pressure and temperature, due to an increase in sulfur solubility and to favorable entropy contributions for bisulfide vs. chloride complexes.〈/span〉

Description: Due to the presence of additional volatiles and/or electrolytes in CO 2 -H 2 O fluids, the total pressure of many natural aqueo-carbonic fluid inclusions at high temperatures as determined using microthermometry is usually made with considerable uncertainty. In this paper, we present the results of our high P - T in situ Raman scattering study of high-density aqueo-carbonic fluids, with and without a small amount of CH 4 and NaCl, whose objective is to derive a new method for pressure determination in aqueo-carbonic fluid inclusions at high temperatures. The measurement of the Fermi dyad bands at temperatures up to 400 °C and pressures up to 1200 MPa is described. The manner in which the frequency shifts and intensity of Raman bands are governed by pressure, temperature, presence of CH 4 in carbonic and NaCl in aqueous fluids is discussed. From the monotonic dependence of the frequency shifts of the lower Fermi dyad band – and the Fermi resonant splitting D ( D = + – – ) with pressure and temperature, the pressure (in MPa) in aqueo-carbonic fluid inclusions at elevated temperatures can be determined directly by using the following two polynomial equations: \[ \begin{array}{l}P\left(\mathrm{MPa}\right)=-16+1.232\times T-53.72\times (\mathrm{\Delta }{\nu }_{-})-1.83\times {10}^{-3}\times {T}^{2}+24.46\times (\mathrm{\Delta }{\nu }_{-}{)}^{2}-0.292\times T\times (\mathrm{\Delta }{\nu }_{-}),\\\relax P\left(\mathrm{MPa}\right)=-26+1.501\times T+193.24\times (\mathrm{\Delta }D)-1.61\times {10}^{-3}\times {T}^{2}+5.436\times (\mathrm{\Delta }D{)}^{2}+0.158\times T\times (\mathrm{\Delta }D),\end{array} \] where T is in °C, – and D represent frequency shifts (in cm –1 ) of the lower band and the resonant splitting relative to the reference values measured at 23 °C and 6 MPa, respectively. Based on the attainable accuracy of the fitted peak positions and the results from fitting of Raman frequency shifts’ dependence with pressure and temperature, the uncertainty in pressure determination is about 50 MPa for pressures determined from – and 40 MPa from that determined from D .

Description: Room-temperature ferrimagnetic and superparamagnetic properties, and the magnetic interactions between the core and shell, of our iron-incorporated chromia-based core shell nanoparticles (CSNs) have been investigated using a combination of experimental measurement and density functional theory (DFT) based calculations. We have synthesized CSNs having an epitaxial shell and well-ordered interface properties by utilizing our hydrothermal nanophase epitaxy (HNE) technique. The ferrimagnetic and superparamagnetic properties of the CSNs are manifested beyond room temperature and magnetic measurements reveal that the exchange bias interaction between the antiferromagnetic (AFM) core and ferrimagnetic (FiM) shell persists close to ambient temperature. The DFT calculations confirm the FiM ordering of the Fe-chromia shell. Our calculations show that the FiM ordering is associated with a band gap reduction, Fe–O d–p orbital hybridization, and AFM type Fe–Cr σ type superexchange interaction in the α-Fe0.40Cr1.60O2.92 shell of the CSNs. The novel magnetic core–shell nanoparticles possess a shell comprised of a metastable Fe(II)-chromia phase, resulting in unique magnetic properties that make them ideal for magnetic device and medicinal applications.