Narrow Results

The effect of temperature on the adsorption of a sulphur atom on the Fe(110) surface has been investigated using molecular dynamics simulations at a temperature of 353K, 373K and 398K. The most favorable adsorption site for a sulphur atom on the Fe(110) is found at a hollow site. The perpendicular height of the sulphur atom position is 4.017Å above the Fe surface at a temperature of 398K. The Fe–S bonding strength was affected by temperature, it becomes weaker with increasing temperature. The adsorption energy is calculated to be −6.640eV, −6.579eV and −1.841eV for the system at a temperature of 353K, 373K and 398K, respectively. This condition is confirmed by experimental results where the corrosion rate of the samples began to appear at 353K, with darker physical characteristics of the corrosion.

Effective systems for the catalytic oxygenation of hydrocarbons have been developed based on metalloporphyrins containing iron, manganese and ruthenium. These metalloporphyrin catalysts were inspired by studies of the mechanism of the heme oxygenase cytochrome P450 and related enzymes. Oxometalloporphyrins, which have now been spectroscopically characterized, have very high reactivity as oxygen transfer agents. A combination of experimental and computational methods has begun to provide an understanding of the structure and reactivity of these oxometalloporphyrin complexes and the mechanisms of oxygen transfer reactions they catalyze.

Synchrotron radiation X-ray fluorescence (SR-XRF) using high energy incident X-rays was combined with micro-PIXE to analyze the renal distribution of Rb and essential elements in immature rats. The Rb concentrations in the kidneys of newborn (1 week old) and young (3 weeks old) rats were 4.19 ± 0.71 and 4.13 ± 0.30 µg/g, respectively, similar to those of adult rats. Rubidium as well as Zn was detected more in the cortex than the medulla, while Fe was concentrated in the outermost areas of the medulla of newborn rats. The renal structures of young rats achieved adult zonation into the cortex, the outer medulla and the inner medulla. Rubidium was high in the outer stripe of the outer medulla. Further analysis at higher resolution revealed Rb in the proximal tubules in the innermost part of the cortex. These results indicated that Rb was distributed downstream of the proximal tubules. This profile was similar to that of potassium, an Rb congener.

The present study aims to analyze the elemental distribution in erythrocytes from five hemodialysis patients treated with erythropoietin in comparison to four healthy controls. Using in-air micro-PIXE we determined that iron dots were distributed in the peripheral region of control erythrocytes, which were made up of two to four compartments. Iron dots tend to aggregate partially in hemodialysis patients. Calcium was rendered to form small dense nodules in erythrocytes of controls, and small dense nodules became marked in some hemodialysis patients. Nodular formation of phosphorous was weakened in both control and hemodialysis patients. Potassium aggregated focally and formed small dense granules in erythrocytes of healthy controls. On the other hand, hemodialysis patients showed enrichment of potassium, with diffuse spreading partially to all over erythrocytes. These findings indicate that in-air micro-PIXE is a useful tool for analyzing the elemental distributions in erythrocytes of hemodialysis patients.

A total of 4269 beard samples were collected from the same person every day over a 12-year period and analyzed by PIXE using a standard-free method. It was found that the concentrations of copper and zinc showed certain short-term changes but did not show a noticeable long-term trend over the study period, with only iron showing a slightly decreasing tendency with age. All of these elements showed clear yearly variations with a cycle of a few years possibly due to periodic metabolic changes in the subject’s body or long-term changes in eating habits. In contrast, however, selenium showed clear seasonal variations. Its concentration significantly increased in the summer and decreased in the winter, just as was observed with arsenic and mercury. This suggests that most of the subject’s selenium intake was from marine products, whose supply and consumption were increased in the summer. These findings confirmed that beard analyses are useful not only for evaluating essential-element intake but also for estimating the relationship between the body-element concentrations and ingestion of certain foods.

The hard tissues of cephalopod, namely statoliths were analyzed with PIXE for the Japanese common squid Todarodes pacificus of the Sea of Japan origin in order to examine the relationship between the amount of trace elements in statoliths and environmental temperature of the squid habitat. Calcium, iron, zinc. copper and strontium were detected in the statoliths. Negative relationship was observed between Sr concentration in statoliths and environmental temperature. On the contrary to Sr, Fe and Zn concentration in statoliths related positively with environmental temperature. These observations revealed that the statoliths would be a useful thermometer for reconstructing the environmental temperature of cephalopod habitat as seen in the hard tissues of other marine organisms.

We report the results of neutron measurements carried out during the application of ultrasounds to bars of iron and steel. Like in our previous similar works with cavitated solutions of iron, neutrons were emitted in bursts and the spectrum of this peculiar emission was measured for the first time. A further and very interesting outcome of these experiments was the unexpected appearance of circular, macroscopical and regular damages on the lateral surface of the bars which was not directly in contact with the sonotrode. The superficial elemental microanalysis on these spots showed some interesting and macroscopic departures of the concentration of chemical elements from that of the undamaged surface, which may suggest that, along with the emission of neutrons, some transmutations occurred as well.

In order to clarify the cracking and failure behavior of gray cast iron brake blocks that are used for the railway applications, macro- and micro observations regarding the cracks and the micro-structure of the used brake blocks were examined. Three brake blocks, which have different degrees of hot spots and cracking during the actual application, were selected for testing. In addition, a thermal-mechanical coupled finite element analysis (FEA) was applied to calculate the temperature and the stress field in the brake blocks during braking. As a result, it was observed that surface cracks were initiated at the hot spots and propagated into the matrix. From the observation of dispersed graphites close to the crack path, it can be said that the deterioration of materials due to the frictional heat of braking made it easy to initiate cracks at the hot spot. The hardness of the brake block was recommended to be under 85 by the Rockwell B scale in order to prevent hot spots and crack initiation. From the FEA, the procedure for the occurrence of hot spots and cracks was successfully simulated by assuming the surface roughness on the slid surface of the brake block.

Annealing study of amorphous bulk and nanoparticle iron at temperatures from 500 K to 1000 K has been carried out using molecular dynamics (MD) simulations. The simulation is performed for models containing 10⁴ particles Fe at both crystalline and amorphous states. We determine changes of the potential energy, pair radial distribution function (PRDF) and distribution of coordination number (DCN) as a function of annealing time. The calculation shows that the aging slightly reduces the potential energy of system. This result evidences that the amorphous sample undergoes different quasi-equilibrated states during annealing. Similar trend is observed for nanoparticles sample. When the samples are annealed at high temperatures we observe the crystallization in both bulk and nanoparticle. In particular, the system undergoes three stages. At first stage the relaxation proceeds slowly so that the energy of system slightly decreases and the samples structure remains amorphous. Within second stage a structural transformation occurs which significantly changes PRDF and DCN for the relatively short time. The energy of the system is dropped considerably and the amorphous structure transforms into the crystalline. Finally, the crystalline sample undergoes the slow relaxation which reduces the energy of system and eliminates structural defects in crystal lattices.

Gupta and Density Functional Theory (DFT) calculations were performed to investigate of structural and magnetic behaviors of 19 atom Fe_nRh${}_{19\text{-}n}$ ($n=0$–19) nanoalloys. A double icosahedron structure was considered for Fe_nRh${}_{19\text{-}n}$ ($n=0$–19) nanoalloys. Significantly, the effects of Fe atom addition on the chemical ordering, stability and total magnetic moments of the nanoalloys were investigated. Local optimization results at the Gupta level show that the Fe atoms are located in the center of the double icosahedron structure and finally in the equatorial region on the surface. The mixing energy analysis obtained that Fe${}_{12}$Rh₇ and Fe₄Rh${}_{15}$ nanoalloys are the most stable compositions at Gupta and DFT levels, respectively. It was found that Fe_nRh${}_{19\text{-}n}$ ($n=0$–19) nanoalloys are energetically suitable for mixing at both Gupta and DFT levels. Also, the bond order parameter result is compatible with the mixing energy analysis result. The total magnetic moments of the Fe_nRh${}_{19\text{-}n}$ ($n=0$–19) nanoalloys increase with the addition of the Fe atom, which is a ferromagnetic metal.

Monodisperse FeCo nanoparticles were synthesized via thermal decomposition of appropriate organometallic complexes in heated toluene containing surfactants, aiming to a soft magnetic nanomaterial with a high metal percent. The particles were characterized by X-ray powder diffraction, electron microscopy, and static magnetometry techniques. The effect of air exposure on the structural and magnetic properties was examined. Portions of the dried nanoparticles were mixed with additional surfactants or polyvinylpyrrolidone, followed by redispersion into tetrahydrofuran, so as to study arrangement features in the first case, while the use of polyvinylpyrrolidone intended to the expansion of the interparticle distances in order to get more "isolated" nanoparticles.

The electronic and magnetic structures of a hydrogenated and hydrogen free superlattice of three iron monolayers and nine vanadium monolayers are studied using the first principle full-potential augmented-plane-wave method as implemented in WIEN2k package. The average and the local magnetic moments of the system are studied versus the hydrogen positions at the octahedral sites within the superlattice and also versus the filling of the vanadium octahedral location by hydrogen atoms. The local Fe magnetic moment and the average magnetic moment per iron atom are found to increase as the H position moves towards the Fe–V interface. On the other hand, the average magnetic moment per Fe atom is found to initially decrease up to filling by three H atoms and then increases afterwards. To our knowledge, this is the first reporting on the increase in the computed magnetic moment with hydrogenation. These trends of magnetic moments are attributed to the volume changes resulting from hydrogenation and not to electronic hydrogen–metal interaction.

An effective-substrate method was presented to obtain the optical constants of an iron native oxide layer with unknown optical constants and film thickness on an iron substrate with unknown optical constants by using spectroscopic ellipsometry (SE). "Thick" iron films were deposited on silicon wafer by magnetron sputtering and were exposed to air at room temperature. They were measured by spectroscopic ellipsometry during this procedure at different time points from ten minutes to seven months. Pseudo optical constants were calculated from the initially measured data and were introduced into the modeling work of subsequent measurements as an effective substrate in order to obtain the optical constants and film thickness of the native oxide layer. After obtaining the optical constants of the subsequent native oxide layer, they were employed in the modeling work of the initially measured data and the optical constants of the iron substrate and the film thickness of the initial native oxide layer was obtained.

The structure and processes of mass, charge and heat transfer are investigated in an equiatomic Fe–Ni composite fabricated by electroconsolidation using the spark plasma sintering (SPS) technology. The system contains regions of almost pure Fe and Ni, separated by areas with variable concentration of components, formed in consequence of the interdiffusion in the electroconsolidation process. The interdiffusion coefficient of the Fe–Ni system has been revealed to be significantly higher than that of an alloy of a similar composition at the same temperature, which is likely the result of the employed SPS technology and the enhanced diffusion along the grain boundaries. The concentration dependence of the interdiffusion coefficient passes through a maximum at a Ni concentration of $\sim$70 at.%. The electrical and thermal conductivity of the studied system is significantly higher than that of an alloy of the same composition. The temperature dependence of the resistivity of the sample in the range 5–300 K is due to the scattering of electrons by defects and phonons, and the scattering of electrons by phonons fits well to the Bloch–Grüneisen–Wilson relation. The boundaries of the conductivity of the investigated composite correspond to the Hashin–Shtrikman boundaries for a three-phase system, if Fe, Ni and the FeNi alloy are selected as phases.

Earth’s core consists of a solid inner core and a liquid outer core, composed primarily of iron. The pressure in the solid inner core is about 330 gigapascals (GPa) at the temperature close to the melting point. Considering the extensive experimental and theoretical data, the shear wave ($s$-wave) velocity of the inner core is much lower than that of pure iron. Since the lower $s$-wave velocity has been observed in the seismic models, reasons have been widely discussed such as the premelting of iron in the Earth’s inner core. In this paper, a new explanation is expected to be proposed under the anisotropic stress. The calculated longitudinal wave and $s$-wave velocity of pure hexagonal close-packed iron (HCP-Fe) model based on the density functional theory (DFT) at the different density are matching with the seismic wave, the atomic distribution of HCP-Fe is obtained under the anisotropic stress. Unfortunately, it is unlikely conformed there was an inner-core condition due to the unreal anisotropic stress, although the lower $s$-wave velocity is. Somehow, this lower $s$-wave velocity may provide a new horizon to build mineralogical models for discussing. In addition, the $s$-wave and viscosity of iron are strongly dependent on shear stress, we then give a mathematical equation between the $s$-wave velocity and viscosity empirically by the shear behavior. It is revealed that the shear stress of iron has a positive influence on the $s$-wave and viscosity.

The growth and structure of ultrathin Rh films on Fe(100) are studied by grazing scattering of 50 keV He projectiles, incident along "random" and low index surface lattice directions. Oscillations in the specular intensity for scattered ions indicate initial layer-by-layer growth, followed by multilayer growth on top of the two-monolayer film. Growth temperatures below about 400 K result in a persistent though rough layer growth up to higher coverages. From distinct maxima in the target current as a function of the azimuthal incidence angle, we deduce that growth is epitaxial and pseudomorphic.

The ion-driven mechanism in hydrogen permeation is substantially modified when iron is coated with palladium. A detailed knowledge of the electronic structure at the metal–metal interfaces is a prerequisite for understanding the process of H permeation. We have selected two low-Miller-index surfaces as a simple model for the interface. The system under consideration has 148 metallic atoms forming an Fe–Pd cluster distributed in six metallic layers.

We have investigated the interaction of atomic hydrogen with the Fe(110)–Pd(100) interface using the semiempirical atom superposition and electron delocalization (ASED-MO) method. The changes in the electronic structures, density of states (DOS) and crystal overlap orbital population (COOP) in two different Fe–Pd interfaces were compared with the bulk ground states of both metals.

The interfacial Fe–Pd distance results in about 1.74 Å, whereas for the Fe–Pd first neighbors distance it is about 1.85 Å. An important conclusion is that the metal–metal bonds at the interface are stronger than those bonds in the pure metal bulk. A favorable metal adhesion is observed, as revealed by the energetic stabilization of the composite metal system.

H is stabilized near the FePd interface and stopped at the first Pd layer. A H–metal bond is developed with both Fe and Pd atoms while Fe–Pd bonding at the interface remains unaltered.

The Fe–C–H interaction near defects in iron structures was studied using qualitative structure calculations in the framework of the atom superposition and electron delocalization molecular orbital. Calculations were performed using three Fe clusters to simulate an edge dislocation, a divacancy; both in bcc iron and a stacking fault in an fcc iron structure. In all cases, the most stable location for C atom inside the clusters was determined. Therefore, H atom was approximated to a minimum energy region where the C atom resides. The total energy of the cluster decreases when the C atom is located near the defects zone. In addition, the presence of C in the defects zone makes no favorable H accumulation. The C acts as an expeller of H in a way that reduces the hydrogen Fe–Fe bonds weakening.

We have investigated the adsorption sites and the electronic structure correlated with the magnetic properties of ultrathin Fe films on W(110) system using spin-polarized calculations within the density-functional approach with generalized gradient approximation by the pseudopotential plane-wave code. For one Fe monolayer (ML) on W(110) system the Fe atoms prefer to bind on the bridge adsorption sites of the W(110) surface, with an inward relaxation of $-$12.68%. The top and diagonal bridge sites investigated are energetically less favorable. We have shown that intermixing between Fe and W is unlikely: the surface ordered Fe–W alloy is unstable against the 1-ML Fe on W(110). While the control of oxygen element is known to be an important key to a perfect growth of Fe on W(110), its possible contamination is checked. Performing spin polarized calculations with the optimized geometry, the induced magnetic moments on W subsurface are obtained: the W atoms are always antiferromagnetically coupled to the Fe atoms, one exception being the case of the antiferromagnetic Fe surface where, due to frustration, the induced polarization on the W atoms is zero. The bridge site is the lower adsorption energy one for O₂ molecular bonding perpendicular to the surface. In the case of O₂ bonding parallel and oblique to the surface, it is always dissociated into two O atoms on Fe/W(110) surface through geometry optimization, for all considered sites.

In order to decrease the decomposition temperature of SiC, 12nm Fe thin film is applied on SiC substrates as a catalyst layer using electron beam (e-beam) deposition. To investigate the mechanism of Fe-treated SiC decomposition, local Fe regions are formed through dewetting of the catalyst layer by hydrogen annealing. The results show that Fe decreases the decomposition temperature of SiC effectively and increases the kinetics of the graphitization. Studies showed that depending on the amount of Fe, crumpled and ordered graphene films can be synthesized simultaneously on SiC by using this method.