Atomistic insights into early stage corrosion of bcc Fe surfaces in oxygen dissolved liquid lead-bismuth eutectic(LBE-O)

Classical molecular dynamics simulations with global neural network machine learning potential are used to study early stage oxidation and dissolution behaviors of bcc Fe surfaces contacting with stagnant oxygen dissolved liquid leadbismuth eutectic(LBE-O).Both static and dynamic simulation results indicate that the early stage oxidation and dissolution behaviors of bcc Fe show strong orientation dependence under the liquid LBE environments,which may explain the experimental observations of uneven interface between iron-based materials and liquid LBE.Our investigations show that it is the delicate balance between the oxide growth and metal dissolution that leads to the observed corrosion anisotropy for bcc Fe contacting with liquid LBE-O.

Embrittlement effects on ferritic/martensitic steels by liquid lead-bismuth eutectic

Studies of synergetic irradiation effects and liquid lead-bismuth eutectic(LBE) corrosion/embrittlement effects on ferritic/martensitic(F/M) steels are of great importance for developing high power spallation neutron targets(>1 M W) such as the European Spallation Source(ESS) and Accelerator Driven System(ADS) facilities that can be used for transmuting long-lifetime radioactive wastes. Liquid LBE(45Pb-55Bi,in terms of mass fraction) has been selected as the candidate target material in high power spallation neutron targets due to its favourable thermal,physical & chemical properties,and to its high spallation neutron yield. 9Cr F/M steels such as T91(9Cr1M oVNb,in terms of mass fraction) have been chosen as the structural material for the targets due to their good mechanical properties and good resistance to irradiation induced swelling in fission neutron irradiation environments. For developing high power spallation neutron targets,behaviors of F/M steels in spallation neutron target irradiation environments and LBE corrosion/embrittlement effects have been extensively studied. However,many open questions have not been answered. The aim of this paper is to describe the present research situation on this topic. The obtained experimental data about LBE embrittlement effects on F/M steels is summarized and the influence of different parameters involved is analyzed to understand the influence effect on LBE embrittlement effect of F/M s.

Effect of silicon on ductility of T91 steel in liquid lead-bismuth eutectic environment

The tensile tests of T91 and T91Si steels at 200-450℃in air and at 350℃in oxygen-depleted liquid lead-bismuth eutectic(LBE)environment with strain rate of 1×10^(-5)-5×10^(-3)were performed.Results show that the activation energy of T91 steel is 103.45-246.76 kJ/mol and that of T91Si steel is 146.98-172.11 kJ/mol when Portevin-Le Chatelie(PLC)phenomenon occurs.The elongation reduction of T91 steel at 350℃is not specific to LBE environment,whereas the presence of LBE promotes crack initiation and propagation and affects the elongation of the material in the necking stage.With Si addition,the elongation,especially the uniform elongation at 350℃in LBE environment,improves,and the tendency toward crack propagation in T91 steel after slow tensile necking is reduced.The PLC phenomenon can be seen in both T91 and T91Si steels at high temperatures owing to the dynamic strain aging(DSA).The temperature ranges are different when DSA occurs,with 300-350℃and 250-350℃for T91 and T91Si steels,respectively.

Cavitation erosion behavior of CLAM steel weld joint in liquid lead-bismuth eutectic alloy

The cavitation erosion of weld joint and base metal of China low activation martensitic（CLAM）steel in liquid lead-bismuth eutectic alloy（LBE）at 550°C was investigated to simulate the cavitation erosion of the first wall and the nuclear main pump impeller in the accelerator driven sub-critical system（ADS）.A suit of ultrasonic cavitation facility was self-designed to study the cavitation erosion.By studying the surface micro topography,roughness and mean pit depth of the tested specimens,it was found that some crater clusters and large scale cracks appeared on the tested specimen surface after the formation of numerous single craters,and the base metal exhibited much better cavitation erosion resistance than the weld bead due to the difference in their mechanical properties and microstructures.In addition,by comparing the results of static corrosion and cavitation erosion,it could be concluded that the cavitation erosion and the dissolution and oxidation corrosion in liquid LBE would accelerate mutually.

Hydrogen diffusion coefficient in liquid metals evaluated by solid-gas eutectic unidirectional solidification

Based on the solid-gas eutectic unidirectional solidification technique and the principle of unidirectional solidification of single-phase alloy, a new method for evaluating the diffusion coefficient of hydrogen in liquid metals was proposed. Taking Cu-H2 system for example, the influences of argon partial pressure and superheat degree of melt on the diffusion coefficient of hydrogen in liquid metal were studied and the predicted values were similar to each other. The obtained temperature-dependent equation for diffusion coefficient of hydrogen in liquid copper is comparable with experimental data in literature, which validates the effectiveness of this method. The temperature-dependent equations for diffusion coefficient of hydrogen in liquid Mg, Si and Cu-34.6%Mn alloy were also evaluated by this method, along with the values at the melting point of each metal and alloy.

Ionic liquids/deep eutectic solvents for CO_(2) capture:Reviewing and evaluating

The CO_(2)solubilities(including CO_(2)Henry’s constant)in physical-and chemical-based ILs/DESs and the COSMO-RS models describing these properties were comprehensively collected and summarized.The summarized results indicate that chemical-based ILs/DESs are superior to physical-based ILs/DESs for CO_(2)capture,especially those ILs have functionalized cation and anion,and superbase DESs;some of the superbase DESs have higher CO_(2)solubilities than those of ILs;the best physical-and chemical-based ILs,as well as physical-and chemicalbased DESs are[BMIM][BF4](4.20 mol kg^(-1)),[DETAH][Im](11.91 mol kg^(-1)),[L-Arg]-Gly 1:6(4.92 mol kg^(-1))and TBD-EG 1:4(12.90 mol kg^(-1)),respectively.Besides the original COSMO-RS mainly providing qualitative predictions,six corrected COSMO-RS models have been proposed to improve the prediction performance based on the experimental data,but only one model is with universal parameters.The newly determined experimental results were further used to verify the perditions of original and corrected COSMO-RS models.The comparison indicates that the original COSMO-RS qualitatively predicts CO_(2)solubility for some but not all ILs/DESs,while the quantitative prediction is incapable at all.The original COSMO-RS is capable to predict CO_(2)Henry’s constant qualitatively for both physical-based ILs and DESs,and quantitative prediction is only available for DESs.For the corrected COSMO-RS models,only the model with universal parameters provides quantitative predictions for CO_(2)solubility in physical-based DESs,while other corrected models always show large deviations(>83%)compared with the experimental CO_(2)Henry’s constants.

Efficient and reversible separation of NH_(3) by deep eutectic solvents with multiple active sites and low viscosities

The efficient separation and collection of ammonia(NH_(3))during NH_(3) synthesis process is essential to improve the economic efficiency and protect the environment.In this work,ethanolammonium hydrochloride(EtOHACl)and phenol(PhOH)were used to prepare a novel class of deep eutectic solvents(DESs)with multiple active sites and low viscosities.The NH_(3) separation performance of EtOHACl+PhOH DESs was analyzed completely.It is figured out that the NH_(3) absorption rates in EtOHACl+PhOH DESs are very fast.The NH_(3) absorption capacities are very high and reach up to 5.52 and 10.74 mol·kg1 at 11.2 and 100.4 kPa under 298.2 K,respectively.In addition,the EtOHACl+PhOH DESs present highly selective absorption of NH_(3) over N_(2) and H_(2) and good regenerative properties after seven cycles of absorption/desorption.The intrinsic separation mechanism of NH_(3) by EtOHACl+PhOH DESs was further revealed by spectroscopic analysis and quantum chemistry calculations.

Microstructure and Solid/Liquid Interface Evolutions of Directionally Solidified Fe-Al-Ta Eutectic Alloy

A modified Bridgman directional solidification technique was used to prepare Fe-Al-Ta eutectic in situ composites at different growth rates ranging from 6 to 80 μm/s. The directionally solidified FeAl-Ta eutectic composites are composed of two phases: Fe（Al,Ta） matrix phase, and Fe2 Ta（Al） Laves phase. Solidification microstructure is affected by solidification rate. Microstructure of the Fe-Al-Ta eutectic alloy grown at 6.0 μm/s is broken-lamellar eutectic. Eutectic colonies are formed with the increase of the solidification rate. Microstructures are mainly composed of the lamellar or fibrous eutectic at the center of the colony and coarse lamellar eutectic zone at the boundary. Meanwhile, the inter-lamellar spacing（or the inter-rod spacing） is decreased. The spacing adjustments are also observed in Fe-Al-Ta eutectic alloy. The solid/liquid interface evolves from planar interface to shallow cellular interface, then to deep cellular, and finally to shallow cellular planar with the increase of the solidification rate.

Effect of Cerium on the Viscosity of Liquid Fe-C Alloy of Eutectic Content

The viscosities of liquid Fe-4.30C and Fe-4.30C-Ce alloys were measured by oscillating crucible viscometer. The results show that viscosity of Fe-4.30C alloy changes from 5.50 to 8.30 MPa·s when the liquid is cooled from 1425 ℃ to the melting point. The abnormity of viscosity of Fe-4.30C alloy near the melting point is reasonable due to the formation of graphite. The addition of cerium especially with content higher than 0.21% causes an evidently decrease in viscosity for eutectic alloy resulting from increase of free volume and size decrease of atom cluster in the liquids. It can be concended that the existence of C-Ce compound contributes to the discontinuous of viscosity at 1340～1370 ℃ for the Fe-4.30C-Ce alloy by experinments with differential scanning calorimeter.

Removal of Basic Nitrogen Compounds from Coker Diesel by Eutectic Ionic Liquid

The eutectic ionic liquid （EIL） tetraethyl ammonium bromide-malonic acid （TEAB-Mal） was synthesized, with its structure characterized by the FT-IR spectroscopy and the 1H NMR spectrometry. The performance for removal of basic nitrogen compounds by EIL was studied using coker diesel as the feedstock. Experimental results showed that the EIL （TEAB-Mal） exhibited a good denitrogenation performance, leading to a 93.6% of basic N-removal efficiency under reaction conditions covering： a temperature of 30 ℃, an EIL to oil mass ratio of 1：1, an extraction time of 30 min, and a settling time of 120 min, while the basic nitrogen content in diesel dropped from 580 μg/g to 37 gg/g. In addition, the efficiency for extraction of basic N-compounds could still reach 62.9% at am EIL/oil mass ratio of 1：7 after four recycles of the EIL.

Fe-based amorphous coating prepared using high-velocity oxygen fuel and its corrosion behavior in static lead-bismuth eutectic alloy

The Fe_(949.7)Cr_(18)Mn_(1.9)Mo_(7.4)W_(1.6)B_(15.2)C_(3.8)Si_(2) amorphous coating was deposited on T91 steel substrate by using the high-velocity oxygen fuel(HVOF)spray technique to enhance the corrosion resistance of T91 stainless steel in liquid lead-bismuth eutectic(LBE).The corrosion behavior of the T91 steel and coating exposed to oxygen-saturated LBE at 400℃ for 500 h was investigated.Results showed that the T91 substrate was severely corroded and covered by a homogeneously distributed dual-layer oxide on the interface contacted to LBE,consisting of an outer magnetite layer and an inner Fe-Cr spinel layer.Meanwhile,the amorphous coating with a high glass transition temperature(Tg=550℃)and crystallization temperature(T_(x)=600℃)exhibited dramatically enhanced thermal stability and corrosion resistance.No visible LBE penetration was observed,although small amounts of Fe_(3)O_(4),Cr_(2)O_(3),and PbO were found on the coating surface.In addition,the amorphicity and interface bonding of the coating layer remained unchanged after the LBE corrosion.The Fe-based amorphous coating can act as a stable barrier layer in liquid LBE and have great application potential for long-term service in LBE-cooled fast reactors.

Photocatalytic oxidative of Keggin-type polyoxometalate ionic liquid for enhanced extractive desulfurization in binary deep eutectic solvents

A series of novel binary deep eutectic solvents(DESs)composed of choline chloride(ChCl)and formic acid(HCOOH)with different molar ratios have been successfully synthesized and applied in extractive desulfurization(EDS).Keggin-type polyoxometallate ionic liquid[TTPh]_(3)PW_(12)O_(40) was prepared and used as catalyst to enhance the EDS capacity by means of photocatalytic oxidative process.Both of the DESs and[TTPh]_(3)PW_(12)O_(40) ionic liquid catalyst were characterized in detail by Fourier transform infrared spectroscopy spectra(FT-IR),elemental analysis,and X-ray photoelectron spectroscopy(XPS).It was found that the molar ratios of Ch Cl:HCOOH had a major impact on desulfurization performance,and the optimal desulfurization capacity 96.5%was obtained by ChCl/5 HCOOH.Besides dibenzothiophene(DBT),the desulfurization efficiencies of 4-methylbenzothiophene(4-MDBT)and 4,6-dimethyldibenzothiophene(4,6-DMDBT),two kinds of DBT derivatives,were also investigated under the same experimental conditions.Moreover,the free radical scavenging experiments manifested that superoxide radical(·O_(2)^(-)) and hole(h^(+)) played important roles in the desulfurization system.After further analysis of the oxidation products by gas chromatography-mass spectrometry(GC–MS),the possible reaction mechanism was proposed.Thus,photocatalytic oxidative has been proved to be one of the efficient approaches for enhancing the extractive desulfurization performance in DES.

Stoichiometry and Stability Constant Values for Copper (II) Chelates with Ethylene Diamine in Deep Eutectic Solvents (DES) (Ethaline) Solutions

In this study we used the deep eutectic solvents (ionic liquids) to investigate the reaction between copper (II) with ethylene diamine (en). Two of the existing methods for analyzing spectrophotometric measurements have been applied for establishing, the stoichiometry and whenever possible, the stability constants of the chelates formed. The method of continuous variations was necessary to determine first whether, the metal ion and the ligand ethylene diamine form one or more than one chelate, when more than one chelate formed, the results obtained depend on the wavelength and for meaningful conclusions the wavelengths were carefully selected. The empirical formulae of the chelates were further substantiated by the molar ratio method. The effect of time and temperature on the formation and stability of these chelates in solution is also studied. The stability constants, K1 and K2 for the copper (II) chelates were calculated, though reliable, and are comparable to literature values.

Ionic Liquids and Deep Eutectic Solvents and Their Use for Dissolving Animal Hair

In recent years, one of the priority areas of research in chemistry has become the processes carried out in an environment of liquid organic salts, the so-called ionic liquids (ILs), which are assessed as environmentally friendly or “green” alternatives to conventional organic solvents. ILs are non-volatile, highly polar solvents that dissolve many organic, inorganic, and organometallic compounds. Since they have no detectable vapor pressure, ILs are considered as potential substitutes for volatile organic compounds traditionally used as solvents. So-called deep eutectic solvents (DES) is a group of ILs that are liquid mixtures of a number of organic and (or) inorganic components taken in a certain ratio (eutectic or close to eutectic). DES deserve a special attention due to their negligible saturated vapor pressure, availability, low cost, as well as ability to dissolve at relatively high concentration of metal salts, metal oxides and various polymers. Particularly DES based on a mixture of choline chloride with urea (DES-1) or a mixture of choline chloride and adduct of urea with hydrogen peroxide (DES-2) give eutectics that are liquid at ambient temperature and have unusual solvent properties, including an ability to dissolve an animal hair in the presence of low concentration of sodium sulfide or ammonium thioglycolate. It was found that depending on the ratio between DES-1 and DES-2 in the mixture of two Deep Eutectic Solvents and the nature of sulfur-containing additive, the solubility of rabbit hair under used conditions, varies from 51% to 79%.

Molar volume of eutectic solvents as a function of molar composition and temperature

The conventional Rackett model for predicting liquid molar volume has been modified to cater for the effect of molar composition of the Deep Eutectic Solvents(DES). The experimental molar volume data for a group of commonly used DES has been used for optimizing the improved model. The data involved different molar compositions of each DES. The validation of the new model was performed on another set of DESs. The average relative deviation of the model on the training and validation datasets was approximately 0.1% while the Rackett model gave a relative deviation of more than 1.6%. The modified model deals with variations in DES molar composition and temperature in a more consistent way than the original Rackett model which exhibits monotonic performance degradation as temperature moves away from reference conditions. Having the composition of the DES as a model variable enhances the practical utilization of the predicting model in diverse design and process simulation applications.

First-Eutectic Features of Polar Metals in Double Systems

It is known that the dense part of any liquid metal consists of ramified clusters of almost regular tetrahedrons (triangular pyramids with atoms in their vertexes) that are connected into chains by faces. Any metal additive as a second component of liquid alloy can be both beyond these clusters as separated atoms and into them as inherent clusters. The liquid-metal alloy transfers into the second state, at the first eutectic of the solvent. This polymorphic transition of liquid matrix is discovered in the systems, Pb-K and Na-Pb, by molecular-dynamic simulating their microstructure and in experiments on scattering slow neutrons by these alloys of different compositions. In the first system, the obtained results identify both the homogeneous alloy at low concentrations of potassium in liquid lead and the alloy clustering, (Pb4K)n, at potassium concentrations following the eutectic, Pb0.91K0.09. In the second one at the concentrations of lead more than 2%, just the second state is discovered with the clusters, (Na4Pb)n. One can expect the same polymorphic transition in the eutectic, Na0.93Tl0.07, with the micro-inhomogeneity, (Na6Tl)n, and with the melting point of 64 C. This eutectic maintained by the oxygen-free technology and enriched by the isotope, 205Tl, can become the best coolant for fast nuclear reactors due to the depressed chemical activity of sodium and composition stability.

Transient liquid phase bonding of Al 2024 to Ti-6Al-4V alloy using Cu-Zn interlayer

Transient liquid phase bonding of two dissimilar alloys Al 2024 and Ti?6Al?4V using Cu?22%Zn interlayer was carried out at 510 °C under vacuum of 0.01 Pa for various bonding time. In order to characterize the microstructure evolution in the joint zone, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were applied. The results show that joint formation is attributed to the solid-state diffusion of Cu and Zn into Ti?6Al?4V and Al 2024 alloys followed by eutectic formation and isothermal solidification along the Cu?Zn/Al 2024 interface. The hardness of the joints at the interface increases with an increase in bonding time which can be attributed to formation of intermetallic compounds such as Al2Cu, TiCu3, Al4.2Cu3.2Zn0.7, Al0.71Zn0.29, Ti2Cu, TiAl3 and TiZn16 in the joint zone. Moreover, shear strength of the joint reaches the highest value of 37 MPa at bonding time of 60 min.

Viscosity of aqueous ionic liquids analogues as a function of water content and temperature

Ionic liquids analogues known as Deep Eutectic Solvents （DESs） are gaining a surge of interest by the scientific community, and many applications involving DESs have been realized. Moisture content is one of the important factors that affects the physical and chemical characteristics of these fluids. In this work, the effect of mixing water with three common type III DESs on their viscosity was investigated within the water tool fraction range of （0-1） and at the temperature range （298.15-353.15 K）. Similar trends of viscosity variation with respect to molar composition and temperature were observed for the three studied systems, Due to the asymmetric geometry of the constituting molecules in these fluids, their viscosity could not be modeled effectively by the conventional Grunberg and Nissan model, and the Fang-He model was used to address this issue with excellent performance. All studied aqueous DES mixtures showed negative deviation in viscosity as compared to ideal mixtures, The degree of intermolecular interactions with water reaches a maximum at a composition of 30% aqueous DES solution. Reline, the most studied DES in the literature, showed the highest deviation. The informa- tion presented in this work on the viscosity of aqueous DES solutions may serve in tuning this important property for diverse industrial applications involving these novel fluids in fluid flow, chemical reactions, liquid-liquid separation and many more.

Origin of the pre-peak in the structure factor of liquid Fe-4.30C-0.21Ce alloy

The liquid structure of Fe-4.30C and Fe-4.30C-0.21Ce alloys was studied by high temperature X-ray diffractometer. The results show that for Fe-C alloy the nearest neighbor distance of the eutectic alloy is 0.259-0.260 nm at the temperature range of 1200-1400℃, which increases to 0.269-0.271 nm with the addition of 0.21% (mass fraction) Ce in the Fe-C alloy at the same temperature range. There is a pre-peak at Q = 15.5 nm-1 on the original intensity curve and structure factor S(Q) of the liquid Fe-4.30C-0.21Ce alloy, which was caused by the Ce atoms in the C-Ce clusters. Combined with the shared face, the tetragonal structure can meet the requirement for the distance of Ce-Ce atoms. It also shows that the cluster size in the liquid Fe-4.30C-0.21Ce alloy increases with the decreasing temperature.

Variants of Nuclear Power Plants of Small and Medium Power with Heavy Liquid-Metal Coolants

New design solutions have been proposed for a BRS-GPG type reactor circuit, which are different from transport and stationary low and medium-powered reactor installations cooled with heavy liquid-metal coolants, and which correspond to the evolutionary development of such installations. While developing these solutions, the available experience in creating and operating Soviet pilot and commercial power plants cooled with lead-bismuth coolants was used, including investigations, primarily experimental ones, carried out by team of authors in justification of a capacity range (50 - 250 MW) of low and medium-powered reactor plants with horizontal steam generators (BRS- GPG) proposed and elaborated at the NNSTU.