arXiv subjects

Ivan Kuzmenko

Publications and source records attributed to Ivan Kuzmenko.

4 recordsLinked to original sources

arXiv2026

Remote epitaxy beyond polarity

Remote epitaxy through a monolayer two-dimensional material-covered substrate establishes a crystallographic registry across the van der Waals (vdW) surface that enables the epitaxial growth, lift-off and transfer of single-crystalline films. A central belief in remote epitaxy is that the substrate facilitating the phenomenon must be a material with strong ionicity, as the interatomic electrostatic potential fluctuation in covalent and metallic materials is substantially attenuated by two-dimensional materials. Here, we show remote epitaxy is possible when the substrate is a metallic or covalently bonded material and experimentally demonstrate non-polar remote homo- and heteroepitaxy across a wide range of material systems, including both metals and semiconductors. The achieved non-polar remote interactions are designed and engineered by harnessing substrate conductivity and vicinal surface step-edge density. These findings indicate that remote epitaxy is universal and applicable to ionic, metallic, and covalent materials, expanding its capabilities and stimulating a plethora of new fundamental scientific questions about the mechanism of remote epitaxy.

cond-mat.mtrl-sci↗

arXiv2023

Correlating Chemical Reaction and Mass Transport in Hydrogen-based Direct Reduction of Iron Oxide

Steelmaking contributes 8% to the total CO2 emissions globally, primarily due to coal-based iron ore reduction. Clean hydrogen-based ironmaking has variable performance because the dominant gas-solid reduction mechanism is set by the defects and pores inside the mm-nm sized oxide particles that change significantly as the reaction progresses. While these governing dynamics are essential to establish continuous flow of iron and its ores through reactors, the direct link between agglomeration and chemistry is still contested due to missing measurements. In this work, we directly measure the connection between chemistry and agglomeration in the smallest iron oxides relevant to magnetite ores. Using synthesized spherical 10-nm magnetite particles reacting in H2, we resolve the formation and consumption of wüstite (FeO) - the step most commonly attributed to agglomeration. Using X-ray scattering and microscopy, we resolve crystallographic anisotropy in the rate of the initial reaction, which becomes isotropic as the material sinters. Complementing with imaging, we demonstrate how the particles self-assemble, subsequently react and sinter into ~100x oblong grains. Our insights into how morphologically uniform iron oxide particles react and agglomerate H2 reduction enable future size-dependent models to effectively describe the multiscale iron ore reduction.

cond-mat.mtrl-sci↗

arXiv2022

Revealing the microstructure of sodium-montmorillonite aqueous suspensions

Aqueous suspensions of geometrically anisometric (2D) sodium-montmorillonite (Na-Mt) particles display a sol-gel transition at very low solids concentrations. The underlying microstructure of the gel has remained a point of contention since the time of Irving Langmuir. An in-situ investigation encompassing length scales much larger than the individual particles is required to provide support for one of the two models proposed in the literature: 1) a percolated network governed by electrostatic attraction between platelets; and 2) a jammed suspension stabilized by repulsive electrostatic forces between particles. We settle this debate by comprehensively probing the microstructure of Na-Mt suspensions using ultra-small angle neutron/X-ray scattering and found that it is ordered and contains entities that are at least an order of magnitude larger than the individual particles. Complementary cryo-electron microscopy showed both the presence of domains having strong particle-particle ordering and regions of particle-particle aggregation. These data indicate 1) the presence of nematic domains, which refutes a purely attractive nature, and 2) assembly of particles, which refutes a purely repulsive nature. Na-Mt gels appear to have a hybrid microstructure with both attractive and repulsive domains.

cond-mat.soft↗

arXiv2004

Surface layering of liquids: The role of surface tension

Recent measurements show that the free surfaces of liquid metals and alloys are always layered, regardless of composition and surface tension; a result supported by three decades of simulations and theory. Recent theoretical work claims, however, that at low enough temperatures the free surfaces of all liquids should become layered, unless preempted by bulk freezing. Using x-ray reflectivity and diffuse scattering measurements we show that there is no observable surface-induced layering in water at T=298 K, thus highlighting a fundamental difference between dielectric and metallic liquids. The implications of this result for the question in the title are discussed.

cond-mat.soft↗