Synthesis and Electrochemistry of O3-type NaFeO2-NaCo0.5Ni0.5O2 Solid Solutions for Na-Ion Positive Electrodes.

The synthesis, structure, and electrochemistry in Na cells of NaFe xM1- xO2 positive electrode materials with M = Ni, Co0.5Ni0.5, and Co are reported. In particular, the properties of O3-NaFeO2-NaCo0.5Ni0.5O2 solid solutions having compositions NaFe x(Co0.5Ni0.5)1- xO2 with 0 ≤ x ≤ 0.5 are explored. It is found that the substitution of Fe in NaNi0.5Co0.5O2 causes an increase in first cycle energy density from 320 to 440 mWh/g in a 1.5-4.0 V test. However, capacity retention is generally reduced when x is increased for all M = Ni, Co0.5Ni0.5, and Co. In general, NaFe xM1- xO2 samples with M = Co had the highest capacity retention for all values of x. Ex situ X-ray diffraction and Mössbauer results of as-prepared and charged materials are directly compared for NaFe x(Co0.5Ni0.5)1- xO2 and NaFe xCo1- xO2 ( x = 0.4, 0.5). Iron was found to be in the +3 oxidation state in the as-prepared materials. A significant fraction of Fe3+ is oxidized to Fe4+ in these samples when they are charged to 4.0 V.

Role of CuO in improving NH3 and SO2 capture on nanoporous Fe2O3 sorbents.

In this work, mixed Fe/Cu oxides as sorbents for SO2 and NH3 removal were investigated. Nanoporous iron oxide mixed with 10, 20 and 30 at.% CuO were prepared by thermal decomposition of the corresponding oxalates at 250 °C for 5 h in air. The mixed Fe/Cu oxalates were obtained from the co-precipitation of iron/copper sulfate and ammonium oxalate during ultrasonication. The physical properties of the oxalate precursors and the resulting mixed Fe/Cu oxides were characterized with SEM, TGA-DSC, FTIR, powder XRD and Mössbauer spectroscopy. The porosity was studied by N2 adsorption-desorption isotherms and small angle X-ray scattering. Evenly dispersed CuO hindered the crystallization of Fe2O3, which significantly increased the specific BET surface area from 211 m2/g for Fe2O3 to 354 m2/g for Fe0.8Cu0.2Ox. As a result, SO2 and NH3 adsorption on Fe0.8Cu0.2Ox were enhanced by about 70% compared to Fe2O3. Compared to Fe2O3-impregnated activated carbons, nanoporous Fe0.8Cu0.2Ox could capture five times more SO2 per unit weight, which will be attractive for applications in respirators with lower weight and smaller size.

Quenched disorder and the critical behavior of a partially frustrated system.

We report the direct observation of the effects of quenched disorder on the critical behavior of partially frustrated amorphous FeMnZr alloys by the systematic analysis of high-precision ac susceptibility data and dc magnetization data. Interestingly, the analysis reveals that the presence of short-range quenched disorder does not alter the actual critical behavior. However, it does affect quantities such as the Curie temperature, the peak value of effective exponent gamma, width of the peak, and crossover temperatures. The observed temperature dependence of the effective critical exponent can be understood in terms of the field-theoretical renormalization group approach. Also, the present results would help in identifying the main source of the spread in the exponent values reported in the literature.

A Mössbauer-effect study of autopsied lung tissue of asbestos workers.

A 57Fe Mössbauer-effect study of autopsied lung tissue from Canadian asbestos mine workers is presented. The spectra typically show large quantities of iron storage protein. This exhibits a quadrupole-split doublet at room temperature and both a doublet and a Zeeman-split sextet at 4.2 K, due to a distribution of particle sizes. A comparison is made with Mössbauer spectra of lung tissue from an individual not occupationally exposed to respirable asbestos, and with spectra of respirable chrysotile asbestos taken from Canadian mines.