Iron Slabs Research Articles

Neutron Importance Estimation via New Recursive Monte Carlo Method for Deep Penetration Neutron Transport

In Monte Carlo neutron transport calculations for local response or deep penetration problems, some estimation of an importance function is generally required in order to improve their efficiency. In this work, a new recursive Monte Carlo (RMC) method, which is partly based on the original RMC method, for estimating an importance function for local variance reduction (i.e., source-detector type) problems has been developed. The new RMC method is applied to two sample problems of varying degrees of neutron penetrations, namely, a one-dimensional iron slab problem and a three-dimensional concrete-air problem. Biased Monte Carlo calculations with variance reduction parameters based on the obtained importance functions by the new RMC method are performed to estimate detector responses in these problems. The obtained results are in agreement with those by the reference unbiased Monte Carlo calculations. Furthermore, the biased calculations offer an increase in efficiency on the order of 1 to 104 in terms of the figure of merit. The results also indicate that the efficiency increased as the neutron penetration became deeper.

Adsorption of imidazolium-based ionic liquids on the Fe(1 0 0) surface for corrosion inhibition: Physisorption or chemisorption?

The use of imidazolium-based ionic liquids (ILs) as corrosion inhibitors for iron was studied using both first-principles based density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD), to understand their adsorption structure, stability, and mechanism. A total of 36 ionic liquids (ILs) were selected, with various anion type (Cl−, Br−, I−, N(CN)2−, BF4− and PF6−) and alkyl chain length (Cn, n = 0, 1, 2, 4 and 6). Our calculations revealed that the ILs exhibit strong adsorption on the metal surface and is classified as chemisorption under various different criteria. AIMD simulations including explicit solvation effects verified that these adsorption configurations calculated under vacuum are representative of the adsorption process in an aqueous environment. Furthermore, we showed that the basis of this chemisorption interaction is through net electron donation from the iron slab to the imidazolium ring. Employing dispersion corrected DFT methods (DFT-D3), we demonstrated that the alkyl chain length of the cation greatly influences adsorption energy. Finally, we showed that DFT calculations model the adsorption process much more accurately compared to classical molecular dynamics calculations. The results from this computational study agree with past experimental findings and demonstrate that DFT calculations can be used to provide insight into the nature of the adsorption process of the green and sustainable ILs involved in corrosion inhibition.

Measurements of gamma and neutron flux spectra in iron-water configurations

Abstract Neutron and gamma spectra were measured behind and inside of modules consisting of variable iron and water slabs which were installed in radial beams of the zero-power training and research reactors AKR of the Technical University Dresden and ZLFR of the University of Applied Sciences Zittau/Görlitz. The applied NE-213 scintillation spectrometer allowed the measurement of gamma and neutron fluence spectra in the energy regions 0.3–10 MeV for photons and 1.0–20 MeV for neutrons. Measurements with thermoluminescence dosemeters (TLD) between slabs supplied additional information about the space distribution of energy integrated fluxes. The paper describes the experiments and presents some important results of the measurements. They will be compared with the results of transport calculations made by means of MCNP and TRAMO in another paper.

Benchmark experiment with iron slab by Time-of-flight technique at CIAE

In order to validate the evaluated nuclear data, leakage spectra in the range of 0.8 to 15 MeV from samples were measured by time-of-flight (TOF) technique using a D-T neutron source. An experimental system for benchmark validation of nuclear data with slab samples has been set up at China Institute of Atomic Energy (CIAE). In this study, test samples are iron slabs, of which the thickness are 5cm, 10cm and 15cm, and the measured angles were chosen to be about 60° and 120°. By comparing measured leakage spectrum with calculated ones by MCNP-4C code, using the data from the CENDL-3.1, ENDF/B-VIII.0, JENDL-4.0 and JEFF-3.3 nuclear data files, and the comparison was made by the spectrum shape and by the C/E values in different energy regions.

Negative and Complex Reluctance in Injective Profile Section

Losses in magnetic circuits are closely related to reluctance. Dealing with coils, transformers, stator poles, rotors in motors, and electromagnets with iron slabs in electrical actuators may raise the question regarding the effect of the slope of section profiles on losses and performance. In this letter, with dc and ac sources, through injective section profiles, we obtain complex, negative, and quantified reluctances. The results suggest that the imaginary part of the reluctance can lead to reduced ferromagnetic materials losses. This means that imaginary reluctance is not always related to electrical conductivity and to power losses but also to the interaction of magnetic flux with the shape of the magnetic core. The imaginary reluctance can be used to increase active and reactive power and reduce magnetic losses. The negative reluctance was effective in reducing magnetic flux and magnetic flux density in a magnetic core.

Mechanism of triboactivity of Schiff bases: Experimental and molecular dynamics simulations studies

Schiff bases derived from o-tolidine through its condensation with salicylaldehyde (OH-BT), naphthaldehyde (H-NT) and 2-hydroxynaphthaldehyde (OH-NT) have been synthesized and characterized by FT-IR and 1H NMR spectroscopic techniques. The synthesized Schiff bases are environmentally safe from tribological aspect as these do not contain undesirable elements like sulfur, phosphorus, and halogens which are known to affect the efficiency of catalytic converters. The triboactivity of these compounds has been studied in paraffin oil (PO) using four-ball tester (FBT) at an optimized concentration of 0.25% w/v under ASTM D4172 and D5183 test conditions. The results have been compared with that of a reference additive, zinc dialkyl dithiophosphate (ZDDP), under similar conditions. Based on tribological data, mean wear scar diameter (MWD), mean wear volume (MWV), coefficient of friction (COF), load carrying ability and wear rate, the following order has emerged for tribological behavior of the investigated additives:OH−BT>OH−NT>H−NT>ZDDP.Morphology and composition of wear scar have been studied by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray analysis (EDX) and relate very well with the observed tribological data. The EDX analysis of the wear scar lubricated with synthesized additives provides evidence for the presence of nitrogen and oxygen. To ascertain the active involvement of the imine group towards tribological behavior, the reaction of the most active compound OH-BT was carried out with thioglycolic acid. Reduced antiwear performance of the reaction product (OH-BTS) may be directly associated with the absence of the imine group (-CH=N-). Molecular dynamics (MD) simulations have been used to study the mechanism of adsorption of the studied Schiff bases in paraffin oil on the iron slab. The order of adsorption energies of the Schiff base additive molecules has been found to agree well with the experimentally observed data. The nature of orientation or configuration of molecules after adsorption has been presented. The findings of the MD simulations have been used to propose the mechanism for tribological behavior of the investigated Schiff base molecules and product OH-BTS obtained by cyclisation of OH-BT with thioglycolic acid. The mechanism proposed from MD simulation studies points to the combined effect of heteroatoms and planarity of the additive molecule after adsorption. Accordingly, molecules with tribological properties of a high order may be formulated.

Benchmarking of evaluated nuclear data for iron by a TOF experiment with slab samples

In order to validate the evaluated nuclear data of iron, neutron leakage spectra in the range from 0.8 to 15 MeV from natural iron slab samples were measured by time-of-flight technique at 60° and 120°, the measurements were performed at China Institute of Atomic Energy (CIAE) using a D-T neutron source, the slab thicknesses were chosen to be 5 cm, 10 cm and 15 cm, corresponding to 1.08, 2.16 and 3.24 mean free paths for 14.5 MeV neutrons, respectively. Theoretical calculations were carried out by Monte Carlo neutron transport code MCNP-4C, using the evaluated nuclear libraries of iron from the CENDL-3.1, ENDF/B-VIII.0, JENDL-4.0, JEFF-3.3, and TENDL-2017. The experimental results were compared with the corresponding calculated ones. From the comparison, it was found that: (1) In the 12–15 MeV range, the results with the ENDF/B-VIII.0 library well reproduce the experimental ones at both 60°and 120°, but those with the JENDL-4.0, JEFF-3.3 and TENDL-2017 libraries are underestimated, especially at 120°; (2) In the 8.5-12 MeV energy range, the calculated neutron spectra with the TENDL-2017 library are underestimated by more than 35%, but those with the JENDL-4.0 library are overestimated around 20%.

The benchmark experiment on slab iron with D-T neutrons for validation of evaluated nuclear data

An experimental system for benchmark validation of nuclear data with slab samples has been set up at China Institute of Atomic Energy (CIAE). Neutron leakage spectra in the range of 0.8–16 MeV from iron slab samples were measured by time-of-flight technique using a D-T neutron source with the measured angle at 60° and 120°. The thicknesses of the slabs were chosen to be 5 cm, 10 cm and 15 cm. The experimental results were compared with the calculated ones by MCNP-4c simulation, using the evaluated data of iron from the CENDL-3.1, ENDF/B-VII.1 and JENDL-4.0 libraries.From the comparison of neutron spectra and the C/Es between the measured and the calculated results, it has been found that some discrepancies in the major reaction channels including (n, p), (n, n′) and (n, 2n) are existing. Detailed information about the neutron product distribution with the evaluated data has been presented to explain the discrepancies which turn out to the data of the above three libraries that needed to be improved as required in different energy ranges.

Initial Irreversible Losses and Enhanced High‐Temperature Performance of Rare‐Earth Permanent Magnets

AbstractThere is an increasing demand for permanent magnets with high‐temperature stability. Normally, the magnets are heat treated above the operating temperature range to saturate the irreversible losses, thereby producing magnets that are stable, but with significantly degraded performance. In addition, uncertainty about the losses in differently shaped magnets causes difficulties for efficient magnetic circuit design. The variation of the initial irreversible losses with magnet shape, hysteresis loop, and operating temperature is presented here. Losses are not associated with thermal demagnetization of the whole magnet, but the damage is concentrated in an outer surface “skin” at the pole surfaces, where the demagnetizing field is nonuniform. The initial irreversible remanence loss at room temperature can be predicted as the product of the slope of the high‐temperature magnetization curvek(T) and the effective demagnetizing factor . Heat treatment with the vulnerable surfaces in contact with soft iron slabs moves the skin out of the permanent magnet and reduces the irreversible remanence loss by 30% or more, potentially improving the performance of permanent‐magnet motors, generators, bearings, and thrusters. The results deepen the understanding of the magnetism of irreversible losses and will guide the applications of permanent magnets at higher temperatures.

Ab initio molecular dynamics study of prebiotic production processes of organic compounds at meteorite impacts on ocean.

Recent experiments concerning prebiotic materials syntheses suggest that the iron-bearing meteorite impacts on ocean during Late Heavy Bombardment provided abundant organic compounds associated with biomolecules such as amino acids and nucleobases. However, the molecular mechanism of a series of chemical reactions to produce such compounds is not well understood. In this study, we simulate the shock compression state of a meteorite impact for a model system composed of CO2 , H2 O, and metallic iron slab by ab initio molecular dynamics combined with multiscale shock technique, and clarify possible elementary reaction processes up to production of organic compounds. The reactions included not only pathways similar to the Fischer-Tropsch process known as an important hydrocarbon synthesis in many planetary processes but also those resulting in production of a carboxylic acid. It is also found that bicarbonate ions formed from CO2 and H2 O participated in some forms in most of these observed elementary reaction processes. These findings would deepen the understanding of the full range of chemical reactions that could occur in the meteorite impact events. © 2018 Wiley Periodicals, Inc.

Zero CO2 steelmaking in a future low carbon economy. 1. Energy conservation in smelting hematite ore directly to refined iron slab

ABSTRACTThe emphasis is on energy conservation. Efficient charge preheating by heat recovery from not only the molten reduction slag but even more important is to eliminate water cooling in the continuous casting of the molten iron, which overflows automatically from the primary melt circulation loop. It is proposed that a liquid metal coolant is used to capture the latent heat of solidification and also the sensible heat associated with cooling the near net shape cast refined iron slab from the melting point down to say 1000°C or so by counter-current radiative heat transfer to secure 800°C charge preheating. The preheated crushed hematite ore plus flux is distributed along the full length of the electrical conductively heated charge incorporation zone of the principal melt circulation loop at a multiple number of locations. The resulting wustite containing thin melt layer floating on the circulating molten iron is counter-currently reduced by hydrogen at atmospheric pressure.

Zero CO2 steelmaking in a future low carbon economy. 2. Secondary steelmaking using refined iron slab, with clean and contaminated scrap

ABSTRACTUse of an electric arc furnace (EAF) with graphite electrodes is incompatible with zero CO2 emission. EAF usage is challenged by proposed new technology employing generic melt circulation, in which no plant-site carbon dioxide is emitted during scrap melting and subsequent continuous refining. The electrical input is estimated to be less than 150 kWh t−1 for processing shredded scrap to near net-shape product. For continuous steelmaking from contaminated scrap, zinc elimination at atmospheric pressure is straightforward. For copper and tin desorption from contaminated molten steel scrap, continuous, evaporation under vacuum, paralleling the commercially established vacuum dezincing of the molten lead carrier medium in the melt circulation loop attached to the condenser of the former zinc–lead blast furnace at Swansea Vale in the UK, is strongly advocated. A case is made for water cooling in final steel product continuous casting to be replaced by heat recovery employing a liquid metal coolant.

Calculating the Bulk Modulus of Iron and Steel Using Equilibrium Molecular Dynamics Simulation

Bulk modulus as one of the important mechanical properties of pure Iron and Steel are calculated using molecular dynamics simulation method. The Iron slab consists of 500 Fe atoms and four different potential functions including two-body and three-body potentials are utilized to predict the bulk modulus for pure Iron. By placing carbon atoms between Fe atoms in a random configuration, we have also calculated the bulk modulus of Steel with 1% carbon concentration. We found that three-body potential functions can predict the bulk modulus of Iron and Steel in agreement with experimental data. All simulations were carried out using LAMMPS package.

Molecular Dynamics Simulation of Heat Transfer during Quenching in CNT Nanofluids

Abstract Nanofluids exhibit superior thermal properties to conventional fluid and particle-fluid suspensions and show a great potential as quenching media for quench hardening of steel components. The heat transfer mechanism in nanofluid is very complex and unclear. In this paper, molecular dynamics (MD) simulation method is used to theoretically study the heat transfer from a metal surface at different temperatures to a water-based nanofluid with functionalized carbon nanotubes (FCNTs). To model the quenching process, an initial temperature jump between the nanofluid and an iron slab is employed, and non-equilibrium molecular dynamics (NEMD) simulations are performed. The MD results reveal the heat transfer process in the initial stage of quenching and at the first moment of contact of a liquid nanofluid with a hot metal surface. The thermodynamics and transport properties of the nanofluid and the heat transfer characteristics are discussed with the atomistic details of the interactions of the FCNT with the iron atoms and the water molecules.

Magnetocrystalline anisotropy energy ofFe(001)andFe(110)slabs and nanoclusters: A detailed local analysis within a tight-binding model

We report tight-binding (TB) calculations of magnetocrystalline anisotropy energy (MAE) of Iron slabs and nanoclusters with a particuler focus on local analysis. After clarifying various concepts and formulations for the determination of MAE, we apply our realistic TB model to the analysis of the magnetic anisotropy of Fe$(001)$, Fe$(110)$ slabs and of two large Fe clusters with $(001)$ and $(110)$ facets only: a truncated pyramid and a truncated bipyramid containg 620 and 1096 atoms, respectively. It is shown that the MAE of slabs originates mainly from outer layers, a small contribution from the bulk gives rise, however, to an oscillatory behavior for large thicknesses. Interestingly, the MAE of the nanoclusters considered is almost solely due to $(001)$ facets and the base perimeter of the pyramid. We believe that this fact could be used to efficiently control the anisotropy of Iron nanoparticles and could also have consequences on their spin dynamics.

NESSiE: An experimental search for sterile neutrinos with the CERN-SPS beam

NESSiE (Neutrino Experiment with SpectrometerS in Europe) is an experiment dedicated to the search for sterile neutrinos beyond the Standard Model with the CERN-SPS neutrino beam. The experiment is based on two identical LAr-TPC's followed by magnetized spectrometers, observing the electron and muon neutrino events at the “Near” (600m) and “Far” (1300m) positions from the proton target. The main characteristics of the spectrometers are described here. Spectrometers will exploit a classical dipole magnetic field with iron slabs, and a new concept air-core magnet will perform charge identification and muon momentum measurements in the energy range from ∼100MeV to few GeV over a large transverse area (>50m2).

Role of the substrate dynamics: Iron clusters deposited on an iron slab

The deposition of iron clusters on an iron substrate is investigated by means of classical molecular dynamics. The substrate dynamics is incorporated and shown to be a relevant ingredient, which leads to substantial changes of the transition temperatures, and of the thermodynamics of the cluster substrate interacting system. Fe55 clusters on Fe (110) and (111) reconstructed surface orientations were studied, showing a stronger effect of the substrate dynamics for the (111) orientation. In fact, the melting temperature for a free Fe cluster, obtained by molecular dynamics simulations, is of the order of 1000K, significantly lower than the 1812K of bulk iron. When supported on a rigid Fe substrate it corresponds to ≈1400K on both the (110) and (111) orientations. However, when the substrate dynamics is incorporated, the melting temperature changes markedly to ≈1200K on the (110), and to ≈900K on the (111), Fe substrate orientation.

Proximity effects on the spin density waves in X/Cr(001) multilayers (X = Sn, V, and Mn)

We present ab initio density functional calculations of the electronic structure and magnetic properties of X2/Cr36(001) and X1/Cr37(001) multilayers, with X=Sn, V and Mn, to investigate the impact of the proximity effects of the X layers on the spin density waves of the Cr slab. We find different magnetic profiles corresponding to the spin density wave and to the layered antiferromagnetic configurations. The nature of the different magnetic solutions is discussed in terms of the different interfacial environments in the proximity of Sn, V or Mn. The magnetic behavior at the interface is discussed in connection with the electronic structure through the density of electronic states projected at the interfacial X and Cr sites. We compare the results with those previously obtained for Fe3/X1/Cr37/X1(001) multilayers to analyze the role played by the ferromagnetic iron slab.

Empirical expressions for angular deviation of muons transmitted through slabs of iron, lead and uranium

To facilitate the computation of angular deviation of cosmic-ray muons transported through slabs of iron, lead and uranium, we have developed an empirical relation for the angle of deviation with the incident muon energy and the thickness, atomic mass, radiation length and density of the material. This empirical relation can be used for easy calculation of angular deviation of cosmic-ray muons that are proposed for detection of high- Z materials in the presence of materials of low- Z using the muon radiography technique. Our results indicate that uranium and lead can be distinguished from iron while discrimination between lead and uranium is anticipated to face practical difficulties.

Purely Angular Effects of Photon Buildup Factors for Thin Shields of Lead, Iron, Aluminum, and Water

This study investigates purely angular effects on photon buildup factors for slabs with optical thickness up to 10 mean free paths. Photon buildup factors are determined for different slabs, upon which monoenergetic photons between 50 keV and 10 MeV are incident at angles between 0 and 1.48 radians. As the incident angle is increased, the physical slab thickness is reduced to maintain a constant slant-path optical thickness relative to incident photons. This method identifies previously unexplored angular relationships between slab thickness and incident angle. Coupled electron/photon cross sections are used to account for secondary photon effects of bremsstrahlung and electron binding energies. The discrete ordinates code PARTISN is used to determine angular photon buildup factors for ten incident energies and ten incident angles for lead, iron, aluminum, and water slabs. Portions of these results are applicable to other slab geometry buildup studies.