Piezo-to-piezo (P2P) conversion: simultaneous β-phase crystallization and poling of ultrathin, transparent and freestanding homopolymer PVDF films MHz-order nanoelectromechanical vibration.

An unconventional yet facile low-energy method for uniquely synthesizing neat poly(vinylidene fluoride) (PVDF) films for energy harvesting applications by utilizing nanoelectromechanical vibration through a 'piezo-to-piezo' (P2P) mechanism is reported. In this concept, the nanoelectromechanical energy from a piezoelectric substrate is directly coupled into another polarizable material (, PVDF) during its crystallization to produce an optically transparent micron-thick film that not only exhibits strong piezoelectricity, but is also freestanding-properties ideal for its use for energy harvesting, but which are difficult to achieve through conventional synthesis routes. We show, particularly through characterization, that the unprecedented acceleration associated with the nanoelectromechanical vibration in the form of surface reflected bulk waves (SRBWs) facilitates preferentially-oriented nucleation of the ferroelectric PVDF β-phase, while simultaneously aligning its dipoles to pole the material through the SRBW's intense native evanescent electric field .

Shape-dependent oxidation rates of nano-structured silver particles.

Reactive molecular dynamics is used to investigate the oxidation of anisotropic silver nanoparticles (nano-Ag) of various shapes, including sphere, cube, disk, cylinder, triangle, and pyramid. The effect of the nano-Ag initial morphology on their stability and composition during oxidation is quantified. Surface oxidation at 600 K leads to the formation of a core-shell structure for all nano-Ag shapes.

The onset of aerosol Au nanoparticle crystallization: accretion & explosive nucleation.

The crystallization of gold nanoparticles is investigated in the gas-phase by molecular dynamics (MD) that is most relevant to their synthesis by aerosol processes (flame, plasma, or cluster beam deposition). A particle size-dependent metastable region, 200-300 °C wide, is revealed between the melting and freezing points of Au. This region decreases as the MD heating or cooling rates decrease.

Internal Structure of Incipient Soot from Acetylene Pyrolysis Obtained via Molecular Dynamics Simulations.

A series of reactive molecular dynamics simulations is used to study the internal structure of incipient soot particles obtained from acetylene pyrolysis. The simulations were performed using the ReaxFF potential at four different temperatures. The resulting soot particles are cataloged and analyzed to obtain statistics of their mass, volume, density, C/H ratio, number of cyclic structures, and other features.

Aggregation and breakage dynamics of alumina particles under shear by coupled Computational Fluid Dynamics - Discrete Element Method.

Hypothesis: Shear affects simultaneous aggregation and fragmentation of fine particles. Understanding the effect of shear on the dynamics of particle aggregation and break-up is important to predict aggregate size and structure. It is hypothesized that there is a transition from pure breakage of large aggregates to regimes where restructuring and aggregation also play a role as aggregates become smaller.

Silicon-Based Anodes for Li Batteries: Thermodynamics, Structural Analysis, and Li Diffusion.

Quantum mechanical and machine learning models are used to analyze the properties of silicon composite materials and their impact on anode performance. The analysis focuses on addressing challenges related to significant volume expansion during lithiation and provides valuable insights into the Gibbs free energy, chemical potentials, and relative stability of Li and Li species. Furthermore, the study explores how Li ions behave in the primary and secondary phases of the anode, assessing the impact of their formation on ion diffusion.

Particle Engineering via Supramolecular Assembly of Macroscopic Hydrophobic Building Blocks.

Tailoring the hydrophobicity of supramolecular assembly building blocks enables the fabrication of well-defined functional materials. However, the selection of building blocks used in the assembly of metal-phenolic networks (MPNs), an emerging supramolecular assembly platform for particle engineering, has been essentially limited to hydrophilic molecules. Herein, we synthesized and applied biscatechol-functionalized hydrophobic polymers (poly(methyl acrylate) (PMA) and poly(butyl acrylate) (PBA)) as building blocks to engineer MPN particle systems (particles and capsules).

Nucleation Rate of N and O in Cryogenic H and He.

The homogeneous nucleation of N and O in cryogenic H and He is investigated by using classical molecular dynamics (MD) simulations. The nucleation kinetics of N and O clusters, including nucleation rate, critical cluster size, and cluster energy, are elucidated in H and He carrier gas at thermalization temperatures of 30-80 K and initial gas densities of 5.65 × 10-2 × 10 m.

Exploiting Molecular Dynamics in Composite Coatings to Design Robust Super-Repellent Surfaces.

Fluorinated motifs are promising for the engineering of repellent coatings, however, a fundamental understanding of how to effectively bind these motifs to various substrates is required to improve their stability in different use scenarios. Herein, the binding of fluorinated polyhedral oligomeric silsesquioxanes (POSS) using a cyanoacrylate glue (binder) is computationally and experimentally evaluated. The composite POSS-binder coatings display ultralow surface energy (≈10 mJ m ), while still having large surface adhesions to substrates (300-400 nN), highlighting that super-repellent coatings (contact angles >150°) can be readily generated with this composite approach.

Interfacial piezoelectric polarization locking in printable TiCT MXene-fluoropolymer composites.

Piezoelectric fluoropolymers convert mechanical energy to electricity and are ideal for sustainably providing power to electronic devices. To convert mechanical energy, a net polarization must be induced in the fluoropolymer, which is currently achieved via an energy-intensive electrical poling process. Eliminating this process will enable the low-energy production of efficient energy harvesters.

Exploiting Supramolecular Dynamics in Metal-Phenolic Networks to Generate Metal-Oxide and Metal-Carbon Networks.

Supramolecular complexation is a powerful strategy for engineering materials in bulk and at interfaces. Metal-phenolic networks (MPNs), which are assembled through supramolecular complexes, have emerged as suitable candidates for surface and particle engineering owing to their diverse properties. Herein, we examine the supramolecular dynamics of MPNs during thermal transformation processes.

Modular Assembly of Host-Guest Metal-Phenolic Networks Using Macrocyclic Building Blocks.

The manipulation of interfacial properties has broad implications for the development of high-performance coatings. Metal-phenolic networks (MPNs) are an emerging class of responsive, adherent materials. Herein, host-guest chemistry is integrated with MPNs to modulate their surface chemistry and interfacial properties.

Condensation and dissociation rates for gas phase metal clusters from molecular dynamics trajectory calculations.

In gas phase synthesis systems, clusters form and grow via condensation, in which a monomer binds to an existing cluster. While a hard-sphere equation is frequently used to predict the condensation rate coefficient, this equation neglects the influences of potential interactions and cluster internal energy on the condensation process. Here, we present a collision rate theory-molecular dynamics simulation approach to calculate condensation probabilities and condensation rate coefficients.

Mobility and settling rate of agglomerates of polydisperse nanoparticles.

Agglomerate settling impacts nanotoxicology and nanomedicine as well as the stability of engineered nanofluids. Here, the mobility of nanostructured fractal-like SiO agglomerates in water is investigated and their settling rate in infinitely dilute suspensions is calculated by a Brownian dynamics algorithm tracking the agglomerate translational and rotational motion. The corresponding friction matrices are obtained using the HYDRO++ algorithm [J.

Surface Composition and Crystallinity of Coalescing Silver-Gold Nanoparticles.

Bimetallic nanoparticles exhibit catalytic, optical, electronic, and magnetic synergy between their constituent metals. Typically, that synergy is traced to the domain structure and surface characteristics of such particles. Here these characteristics of coalescing Ag-Au nanoparticles of various initial sizes and morphologies (segregated or alloys) are investigated by atomistic molecular dynamics (MD) at different temperatures.

Coagulation-agglomeration of fractal-like particles: structure and self-preserving size distribution.

Agglomeration occurs in environmental and industrial processes, especially at low temperatures where particle sintering or coalescence is rather slow. Here, the growth and structure of particles undergoing agglomeration (coagulation in the absence of coalescence, condensation, or surface growth) are investigated from the free molecular to the continuum regime by discrete element modeling (DEM). Particles coagulating in the free molecular regime follow ballistic trajectories described by an event-driven method, whereas in the near-continuum (gas-slip) and continuum regimes, Langevin dynamics describe their diffusive motion.