^(57)Fe Mssbauer spectroscopic study on the barks of several three species grown in Lanzhou, China

Using 57 Fe Mssbauer effect, the chemical states of iron components were investigated for the barks of Platycladus orientalis, Cedrus deodara and Platanus acerifolia sampled from Lanzhou City, China. All bark samples showed two overlapping doublets with large and small quadruple splitting. Only Platycladus orientalis's barks exhibited one sextet. Based on Mssbauer parameters, they were attributed to paramagnetic ferrous, paramagnetic ferric and magnetic iron, respectively. For the sampling site which is about 6 kilometers from Lanzhou Steel Factory, the ratio of ferrous to ferric was higher in the sample of Platanus acerifolia's barks, whereas the barks of Platycladus orientalis and Cedrus deodara gave similar values of this ratio. Platycladus orientalis was the most effective in accumulating iron complexes in barks among the three trees. Platanus acerifolia's barks sampled at Lanzhou Steel Factory's area exhibited higher absolute intensities of iron components and lower ration of ferrous to ferric, indicating that industrial air pollution is a contributing factor in accumulating iron compounds in the tree barks of this region.

Topotactically constructed nickel-iron(oxy)hydroxide with abundant in-situ produced high-valent iron species for efficient water oxidation

The low efficiency of oxygen evolution reaction(OER) is regarded as one of the major roadblocks for metal-air batteries and water electrolysis.Herein,a high-performance OER catalyst of NiFe_(0.2)(oxy)hydroxide(NiFe_(0.2)-O_(x)H_(y)) was developed through topotactic transformation of a Prussian blue analogue in an alkaline solution,which exhibits a low overpotential of only 263 mV to reach a current density of 10 mA cm^(-2) and a small Tafel slope of 35 mV dec-1.Ex-situ/operando Raman spectroscopy results indicated that the phase structure of NiFe_(0.2)-O_(x)H_(y) was irreversibly transformed from the type of α-Ni(OH)_(2) to γ-NiOOH with applying an anodic potential,while ex-situ/operando 57Fe Mossbauer spectroscopic studies evidenced the in-situ production of abundant high-valent iron species under OER conditions,which effectively promoted the OER catalysis.Our work elucidates that the amount of high-valent iron species in-situ produced in the NiFe(oxy)hydroxide has a positive correlation with its water oxidation reaction performance,which further deepens the understanding of the mechanism of NiFe-based electrocatalysts.

Research on the dissolution behavior of cementite in the GCr15 steel surface layer induced by surface nanocrystallization

Dissolution of cementite was found in the surface layer of 1.0C-1.5Cr steel plates during the process of surface mechanical attrition treatment(SMAT),and its evolution was characterized by transmission electron microscope(TEM),three-dimensional atom probe(3DAP)and Mssbauer spectroscopy.The average grain size contained in the top surface of SMAT specimen was 10nm,and no diffraction ring corresponding to cementite grain was identified in the selected area election diffraction(SAED)pattern,which indicated the disappearance of cementite.3DAP analysis showed the average carbon concentration in ferrite(0.75 at%)after SMAT,which was almost 100 times higher than that in matrix(0.008 at%),which suggested cementite dissolve in the process of SMAT.The results of Mssbauer spectroscopy indicated that partial cementite dissolved in the process of SMAT,the saturation of cementite dissolution is about 47%.Evolution of cementite involved three sub-stages:①inoculation stage,in the first 5 min of treated duration,cementite fraction is reduced only by 0.4%;②dissolution stage,within the following 25 min cementite fraction significantly is reduced from 14.6% to 8.4%;③saturation stage,when treatment exceeds 30 min,the fraction of cementite nearly remains the same.

Investigation on Supported Iron Catalyst for Fischer-Tropsch Synthesis

The supported iron catalyst Fe 2O 3 La 2O 3 γ Al 2O 3 has been studied by temperature programmed reduction(TPR) and Mssbauer spectroscopy(MES). The results show that this catalyst, in which the carrier γ Al 2O 3 is modified by La 2O 3, exhibits much stronger active component support interaction, stabilizes the ferrous phase and thus is more difficult to reduce to α Fe. Meanwhile no iron carbide can be detected after Fischer Tropsch synthesis accounting for a strong interaction between the active phase and the carrier.

Quantitative Mossbauer Study on Retained Austenite and Carbide in High Speed Steel

The retained austenite in high speed steel of two different heat treatment regimes was quantitatively,determined by transmission Mssbauer spectroscopy (TMS),backscattering X-ray geometry,Mossbauer spectroscopy (BXMS) and X-ray diffraction technique.The results meas- ured by these methods were in agreement with each other.It was demonstrated that the concentration of carbides in high speed steel could be measured by transmission Mossbauer spectroscopy or Mossbau- er spectroscopy in backscattering X-ray geometry accurately.

Structure and magnetic properties of melt-spun Sm-Fe-Nb ribbons and their nitrides

SmFe（10-x）Nbx（x = 0, 0.1, 0.2, 0.3） ribbons and their nitrides were prepared by melt-spinning, followed by annealing and subsequent nitriding. The structure and magnetic properties were investigated by means of X-ray diffraction（XRD） using the Rietveld method, vibrating sample magnetometer（VSM）, transmission electron microscope（TEM） and Mossbauer spectroscopy. XRD analysis shows that the addition of Nb can impede the precipitation of Sm2 Fe（17） and a-Fe phases and the Nb atoms occupy 2 e site in the alloys. At 300 K, the mean hyperfine fields of 2 e site are 29.58 T with Nb doping at x = 0.1 and the corresponding Curie temperature is 552 K. The optimal properties of remanence of Br = 0.9 T, intrinsic coercivity of H（cj）= 741.5 kA·m^-1, and maximum magnetic energy product of（BH）（max）= 124.2 kJ·m-（-3） are gained at x = 0.10 in the nitrides.