There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Abstract Surface energies of Si(0 0 1), (1 1 0), (1 1 1), and (1 1 3) surfaces with different reconstructions are calculated systematically using first-principles total-energy method. In order to quantitatively compare their relative stability, the surface energies of different surface orientations and their respective theoretical bulk atom energies are determined simultaneously by linear fitting slab supercell total energy as a function of the atom number in the slab. Equivalent computational parameters and convergence criteria are used for all calculations. Without considering entropy contribution, the relative stability of these Si surfaces with given reconstructions is shown, in decreasing order, from (1 1 1) to (0 0 1) and (1 1 3) at low temperature, and from (0 0 1), (1 1 3), (1 1 0), to (1 1 1) at high temperature.

/pdf/relative-stability-of-si-surfaces-a-first-principles-study-2fnylu9w2a.pdf

Relative stability of Si surfaces: a first-principles study

Aluminum matrix composites loaded with various fractions of multi-walled, well-structured boron nitride nanotubes (BNNTs), up to 5 wt.% fractions, were fabricated using powder constituents by means of a high pressure torsion technique (HPT) at room temperature under 5 GPa pressurization. Transient ultrathin amorphous-like layers, with a thickness of 2–5 nm, composed of Al(BNO) phases, which formed under severe plastic deformation and developed under further heat treatments of the composites at 350 °C and 450 °C, were detected at the interfacial regions between Al grains and tightly embracing them BN layers. Room temperature hardness and tensile tests on fabricated composites before and after heat treatments were conducted. The highest value of room temperature tensile strength was obtained on Al-5 wt.% BNNT samples annealed at 450 °C, that reached up to ~ 420 MPa, thus exhibiting more than a doubled increase in strength compared to HPT-fabricated pure Al samples under identical compacting conditions.

Aluminum matrix composites reinforced with multi-walled boron nitride nanotubes fabricated by a high-pressure torsion technique

Redox performance of Na-modified Fe2O3/Al2O3 with syngas as reducing agent in chemical looping combustion process

Microstructure evolution during AlSi10Mg molten alloy/BN microflake interactions in metal matrix composites obtained through 3D printing

For a successful implementation of newly proposed silicon-based latent heat thermal energy storage systems, proper ceramic materials that could withstand a contact heating with molten silicon at temperatures much higher than its melting point need to be developed. In this regard, a non-wetting behavior and low reactivity are the main criteria determining the applicability of ceramic as a potential crucible material for long-term ultrahigh temperature contact with molten silicon. In this work, the wetting of hexagonal boron nitride (h-BN) by molten silicon was examined for the first time at temperatures up to 1750 °C. For this purpose, the sessile drop technique combined with contact heating procedure under static argon was used. The reactivity in Si/h-BN system under proposed conditions was evaluated by SEM/EDS examinations of the solidified couple. It was demonstrated that increase in temperature improves wetting, and consequently, non-wetting-to-wetting transition takes place at around 1650 °C. The contact angle of 90° ± 5° is maintained at temperatures up to 1750 °C. The results of structural characterization supported by a thermodynamic modeling indicate that the wetting behavior of the Si/h-BN couple during heating to and cooling from ultrahigh temperature of 1750 °C is mainly controlled by the substrate dissolution/reprecipitation mechanism.

/pdf/wetting-behavior-and-reactivity-of-molten-silicon-with-h-bn-17mnnpfxe3.pdf

Wetting Behavior and Reactivity of Molten Silicon with h-BN Substrate at Ultrahigh Temperatures up to 1750 °C

In hot metal desulphurisation (HMD) the slag will hold the removed sulphur. However, the iron that is lost when the slag is skimmed off, accounts for the highest costs of the HMD process. These iron losses are lower when the slag has a lower viscosity, which can be achieved by changing the slag composition. A lower slag basicity decreases the viscosity of the slag, but also lowers its sulphur removal capacity, therefore optimisation is necessary. In this study, the optimal HMD slag composition is investigated, considering both the sulphur removal capacity and the iron losses. In part I the theory is discussed and in part II the optimal slag is validated with plant data, laboratory experiments and a thermodynamic analysis.

https://www.tandfonline.com/doi/pdf/10.1080/03019233.2021.1882647

Optimal hot metal desulphurisation slag considering iron loss and sulphur removal capacity part I : fundamentals

Thermodynamic modeling of the sulfide dissolution in the Na2O–FetO–CaO–MgO–MnO–Al2O3–SiO2 multicomponent slags was performed to investigate the desulfurization of hot metal using Na2O-containing fluxes. The dissolution behavior of sulfur in the melts was modeled using the modified quasi-chemical model in the quadruplet approximation. This model can take into account the short-range ordering and the reciprocal exchange reaction of cations and anions in oxy-sulfide slags. Experimental sulfide capacity data were well predicted from the model with only three model parameters.

Thermodynamic Modeling of Sulfide Capacity of Na2O-Containing Oxide Melts

A complete literature review, critical evaluation, and thermodynamic optimization of phase diagrams and thermodynamic properties of the Na2O-FeO-Fe2O3-SiO2 system were performed at 1 atm total pressure. A set of optimized model parameters obtained for all phases present in this system reproduces available and reliable thermodynamic properties and phase equilibria within experimental error limits from 298 K (25 °C) to above liquidus temperatures for all compositions and oxygen partial pressures from metallic Fe saturation to 1 atm. The liquid phase was modeled based on the Modified Quasichemical Model considering the possible formation of NaFeO2 associate in the liquid state. The NaFeO2 metaoxide solid solutions containing the excess SiO2 were described within the framework of Compound Energy Formalism. Based on the thermodynamic models and model parameters, unexplored thermodynamic properties and phase diagrams of the Na2O-FeO-Fe2O3-SiO2 system were predicted.

Critical Evaluation and Thermodynamic Optimization of the Na2O-FeO-Fe2O3-SiO2 System

Abstract A critical assessment and thermodynamic optimization of phase diagrams and thermodynamic properties of the entire Na2O–FeO–Fe2O3–Al2O3–SiO2 system were carried out at 1 atm total pressure. A set of optimized model parameters obtained for all phases present in this system reproduces available and reliable thermodynamic property and phase equilibrium data within experimental error limits from 298 K to above liquidus temperatures for all compositions and oxygen partial pressures from metallic Fe saturation to 1 atm. The Gibbs energy of liquid solution was described based on the Modified Quasichemical Model considering the possible formation of NaAlO2 and NaFeO2 associates in the liquid state. The solid solutions wustite, spinel, feldspar, nepheline, carnegieite, mullite, corundum, clino-pyroxene, meta-oxides and Na-β″-alumina were treated within the framework of Compound Energy Formalism. The database of model parameters can be used to calculate any thermodynamic property and phase diagram section of the present system.

Elmira Moosavi-Khoonsari

Papers

Wetting Behavior and Reactivity of Molten Silicon with h-BN Substrate at Ultrahigh Temperatures up to 1750 °C

Optimal hot metal desulphurisation slag considering iron loss and sulphur removal capacity part I : fundamentals

Thermodynamic Modeling of Sulfide Capacity of Na2O-Containing Oxide Melts

Critical Evaluation and Thermodynamic Optimization of the Na2O-FeO-Fe2O3-SiO2 System

Critical evaluation and thermodynamic optimization of the Na 2 O–FeO–Fe 2 O 3 –Al 2 O 3 –SiO 2 system