Effect of Bottom Blowing Mode on Fluid Flow and Mixing Behavior in Converter

Bottom blowing agitation plays a crucial role in improving the reaction kinetics condition of molten bath during the steelmaking process. Herein, the influence of bottom blowing mode on the flow and mixing characteristics of molten bath and the abrasion characteristics of refractory lining in a 6:1 scaled-down model of a 100 t converter were investigated using physical and numerical simulations together. Eight bottom blowing modes were designed (uniform, three-point linear co-direction, three-point linear unco-direction, two-point linear, circumferential linear, A-type, V-type, and triangle alternating). The results indicated that bottom blowing mode has a significant effect on the local flow field at the inner ring of bottom tuyeres, the velocity interval distribution, and the turbulent kinetic energy, which in turn determines the tracer diffusion path and rate as well the mixing time of molten bath. Reasonable non-uniform bottom blowing modes promote the interaction between the various stirring sub-zones of the molten bath. Among them, the three-point linear co-direction mode and A-type mode have the highest mixing efficiency under the conditions of bottom blowing and combined blowing, respectively, which is superior to the uniform mode. In addition, the bottom blowing mode changed the location and degree of abrasion of the refractory lining, and the total abrasion of the non-uniform mode was reduced. The average value and fluctuation degree of integral wall shear stress for the A-type mode were minimal.

First-principles investigation of copper diffusion barrier performance in defective 2D layered materials

This paper investigates the diffusion barrier performance of 2D layered materials with pre-existing vacancy defects using first-principles density functional theory. Vacancy defects in 2D materials may give rise to a large amount of Cu accumulation, and consequently, the defect becomes a diffusion path for Cu. Five 2D layered structures are investigated as diffusion barriers for Cu, i.e., graphene with C vacancy, hBN with B/N vacancy, and MoS2 with Mo/2S vacancy. The calculated energy barriers using climbing image - nudged elastic band show that MoS2-V2S has the highest diffusion energy barrier among other 2D layers, followed by hBN-VN and graphene. The obtained energy barrier of Cu on defected layer is found to be proportional to the length of the diffusion path. Moreover, the diffusion of Cu through vacancy defects is found to modulate the electronic structures and magnetic properties of the 2D layer. The charge density difference shows that there exists a considerable charge transfer between Cu and barrier layer as quantified by Bader charge. Given the current need for an ultra-thin diffusion barrier layer, the obtained results contribute to the field of application of 2D materials as Cu diffusion barrier in the presence of mono-vacancy defects.

SnSe/Cu2SnSe3 Heterojunction Structure with High Initial Coulombic Efficiency for Lithium-Ion Battery Anodes

Due to high theoretical specific capacity and abundant reserves, tin selenide-based materials have received tremendous attentions in the fields of lithium-ion batteries. Nevertheless, the huge volume changes during insertion/de-intercalation processes deteriorate the Coulombic Efficiency greatly. In order to solve it, the researchers have made great efforts by means of controlling nanoparticles granularity, carbon coating, ion doping et al. In this study, SnSe/Cu2SnSe3 heterojunction nanocomposites were synthesized by solvo-thermal method. The resulting SnSe/Cu2SnSe3 is a three-dimensional flower-like hierarchical nanostructure composed of nanoscale thin lamellae of a thickness of 8-12 nm. The unique nanostructure could shorten the diffusion path of lithium ions and expedite charge transfer, and therefore enhance the reaction kinetics. Compared with SnSe, the initial Coulombic efficiency of SnSe/Cu2SnSe3 is raised from 59% to 90% as the anode material of lithium-ion batteries.

Damage Analysis in Ag Nanoparticle Interconnect Line Under High-Density Electric Current

Printed electronics (PEs) have attracted attention for the fabrication of microscale electronic circuits. PEs use conductive inks which include metal nanoparticles. The conductive ink can be printed on flexible substrates for wearable devices using ink-jet printers and roll-to-roll methods. With the scaling down of electric devices, the current density and Joule heating in the device lines increase, and electromigration (EM) damage becomes significant. EM is a transportation phenomenon of metallic atoms caused by the electron wind under high-density current. Reducing the EM damage is extremely important to enhance the device reliability. With the progress in miniaturization of the metal nanoparticle ink lines, EM problem needs to be solved for ensuring the reliability of these lines. We know that the formation of aggregates and cathode damages occur due to a current loading. The diffusion path of atoms due to the EM has not been identified under the high-density current loading. In this study, a high-density electric current loading was applied to an Ag nanoparticle line. The line specimens were prepared using a lift-off method. After the current loading tests, observations were conducted using a laser microscope and scanning electron microscope. A local decrease in the line thickness and scale-shaped slit-like voids were observed due to the high-density current loading. Moreover, the microstructure of the line was modified by enlarging the Ag grain. From the results, we identified that a dominant diffusion occurred at the Ag grain boundary due to the EM.

Advancing towards a Practical Magnesium Ion Battery

A post-lithium battery era is envisaged, and it is urgent to find new and sustainable systems for energy storage. Multivalent metals, such as magnesium, are very promising to replace lithium, but the low mobility of magnesium ion and the lack of suitable electrolytes are serious concerns. This review mainly discusses the advantages and shortcomings of the new rechargeable magnesium batteries, the future directions and the possibility of using solid electrolytes. Special emphasis is put on the diversity of structures, and on the theoretical calculations about voltage and structures. A critical issue is to select the combination of the positive and negative electrode materials to achieve an optimum battery voltage. The theoretical calculations of the structure, intercalation voltage and diffusion path can be very useful for evaluating the materials and for comparison with the experimental results of the magnesium batteries which are not hassle-free.

Study on Dust Control Technology in Artillery Working Face

Aiming at the serious problem of dust pollution in blasting work, the dust generation law and dust-bearing air flow time and space evolution law of blasting working face is analyzed and studied, and the optimal dust-exhausting wind speed of blasting work was 1.5 m/s. Combining with the dust production characteristics and wind speed conditions of the 107 blasting face in Dongling Coal Mine, Chongqing, Comprehensive dust prevention measures such as high-efficiency water cannon mud, high-pressure spray dust reduction, and dust concentration over-limit spray dust reduction are adopted to control the dust from the source and cut off the dust diffusion path, and the total dust reduction efficiency reached 94.8%, the respirable dust reduction efficiency reached 92%, and a good dust reduction effect has been achieved, which provides a basic basis for the control of dust in the blast mining work.

hBN Flake Embedded Al2O3 Thin Film for Flexible Moisture Barrier

Due to the vulnerability of organic optoelectronic devices to moisture and oxygen, thin-film moisture barriers have played a critical role in improving the lifetime of the devices. Here, we propose a hexagonal boron nitride (hBN) embedded Al2O3 thin film as a flexible moisture barrier. After layer-by-layer (LBL) staking of polymer and hBN flake composite layer, Al2O3 was deposited on the nano-laminate template by spatial plasma atomic layer deposition (PEALD). Because the hBN flakes in Al2O3 thin film increase the diffusion path of moisture, the composite layer has a low water vapor transmission ratio (WVTR) value of 1.8 × 10−4 g/m2 day. Furthermore, as embedded hBN flakes restrict crack propagation, the composite film exhibits high mechanical stability in repeated 3 mm bending radius fatigue tests.

MAPbI3 Deposition by LV-PSE on TiO2 for Photovoltaic Application

Hybrid perovskites are one of the most popular materials nowadays due to their very exclusive properties. To mitigate costs, complexity, and environmental impact, in this work, we have prepared methylammonium lead iodide (MAPbI3) films by a two-step Low-Vacuum Proximity-Space-Effusion (LV-PSE). The LV-PSE method exploits the low vacuum and the short diffusion path from the precursor source to have high thermal energy and partial pressure of the sublimated species close to the substrate. To this aim, the substrate is located at a medium distance (∼2 cm) from the melting pots in a low-vacuum chamber at ∼4 × 10−2 mbar. In the first step, a PbI2 film is deposited on a substrate; in the second step, the conversion into MAPbI3 occurs via an adsorption-incorporation-migration mechanism through the evaporation of methylammonium iodide (MAI) reagents. To exploit the potential of the conversion reaction, 190 nm MAPbI3 layers are deposited on TiO2 substrates. The layers were characterized in terms of crystal structure by X-ray diffraction (XRD) analyses, which showed the exclusive presence of MAPbI3 confirming the complete conversion of the PbI2 film. Scanning Electron Microscopy (SEM) analyses revealed a flat uniform pinhole-free coverage of the substrates and good conformational coverage of the TiO2 underlayer. Transmission Electron Microscopy (TEM) analyses addressed the formation of the tetragonal phase and the absence of the amorphous phase in the film. Spectroscopic ellipsometry (SE) analyses were used to explore the optical properties and the stability of the MAPbI3 layer at different temperatures and ambient conditions. As proof of concept, solar cell architectures were prepared using TiO2 as Electron Transporting Layer (ETL), Spiro-OMeTAD as Hole Transporting Layer (HTL), and Au as a contact to exploit the new up-scalable and clean deposition method. Using just ∼190 nm thick layers, the best efficiency reached with this architecture was 6.30%.

Analysis of CO2 kinetics in Na,Cs-Rho crystals using the zero length column: a case study for slow systems

Experimental measurements of systems with slow gas transport kinetics are generally considered a relatively easier task when compared to the challenges of measurements of very fast systems. On the other hand, when the transport process goes towards time constants of the order of several hours, not only the measurements, but also the analysis and interpretation of the data offer challenges which make the assessment of the correct time constant of the process non trivial. In this work we used the measurements of CO2 diffusion in Na,Cs-Rho crystals, carried out using the zero length column (ZLC) technique, as a case study for the use of the technique for very slow adsorption processes. The system, which has a time constant of the order of 8 h, shows the importance of using the partial loading approach for the determination of an unambiguous time constant from the analysis of the ZLC desorption curves. The traditional analysis is refined by using the nonlinear ZLC model to take into account the isotherm nonlinearity that results in a concentration dependent diffusivity. Finally, the method proposed by Cavalcante is used to confirm the 3-D diffusion path of the system.