Influence of the Degree of Cure in the Bulk Properties of Graphite Nanoplatelets Nanocomposites Printed via Stereolithography

In this work, we report on the fabrication via stereolithography (SLA) of acrylic-based nanocomposites using graphite nanoplatelets (GNPs) as an additive. GNPs are able to absorb UV–Vis radiation, thus blocking partial or totally the light path of the SLA laser. Based on this, we identified a range of GNP concentrations below 2.5 wt %, where nanocomposites can be successfully printed. We show that, even though GNP is well-dispersed along the polymeric matrix, nanocomposites presented lower degrees of cure and therefore worse mechanical properties when compared with pristine resin. However, a post-processing at 60 °C with UV light for 1 h eliminates this difference in the degree of cure, reaching values above 90% in all cases. In these conditions, the tensile strength is enhanced for 0.5 wt % GNP nanocomposites, while the stiffness is increased for 0.5–1.0 wt % GNP nanocomposites. Finally, we also demonstrate that 2.5 wt % GNP nanocomposites possess characteristic properties of semiconductors, which allows them to be used as electrostatic dispersion materials.

Simulation of multiple-component charged aerosol evolution

The study of the nuclear source term requires the computation of aerosol dynamics. Solutions to the aerosol general dynamic equation (GDE) are difficult to obtain by analytical or numerical methods when more realistic problems are considered. The direct simulation Monte Carlo (DSMC) technique is capable of simulating aerosol evolution reducing simplifications in the implementation of the aerosol GDE. In this work we present a DSMC program for the simulation of multi-component polydisperse aerosol evolution, with the successful integration of the following processes: deposition, electrostatic dispersion, coagulation (considering charge effects) and condensation, assuming a spatially homogeneous medium and spherical particles. Two problems with different particle compositions were simulated to obtain information about the interactions through the different processes and the interacting particles as well as particle number and mass distributions with discrimination of charge levels. This information allowed us to explore the synergistic nature of these processes. It was found that the problem with denser particles had an overall stronger activity in coagulation and initially a stronger activity in deposition compared to the problem with less dense particles. Experiments to generate two-component aerosols by spark discharge in the study of aerosol coagulation with characterization of particle composition are proposed. Moreover, the use of particle weights in the DSMC method is explored.

Description of Weak Halogen Bonding Using Various Levels of Symmetry-Adapted Perturbation Theory Combined with Effective Core Potentials

The present work starts with providing a description of the halogen bonding (XB) interaction between the halogen atom of MH3X (where M = C–Pb and X = I, At) and the N atom of HCN. This interaction leads to the formation of stable yet very weakly bound MH3X⋯NCH complexes for which the interaction energy (Eint) between MH3X and HCN is calculated using various symmetry-adapted perturbation theory (SAPT) methods combined with the def2-QZVPP basis set and midbond functions. This basis set assigns effective core potentials (ECPs) not only to the I or At atom directly participating in the XB interaction with HCN but also to the M atom when substituted with Sn or Pb. Twelve SAPT methods (or levels) are taken into consideration. According to the SAPT analysis ofEint, the XB interaction in the complexes shows mixed electrostatic-dispersion nature. Next, the accuracy of SAPTEintis evaluated by comparing with CCSD(T) reference data. This comparison reveals that high-order SAPT2+(3)method and the much less computationally demanding SAPT(DFT) method perform very well in describingEintof the complexes. However, the accuracy of these methods decreases dramatically if they are combined with the so-called Hartree-Fock correction.

STUDY OF ELECTROSTATIC DISPERSION

The article deals with the problems of studying the process of dispersing liquid fuel and water-fuel emulsions, in particular the characteristics of the dispersed spray in high-potential electrostatic fields. The paper deals with the development of a research method for disperse characteristics of liquid fuels, in particular, the changes in the diameter of the spray particles of liquid fuels and water-fuel emulsions based on them, depending on the intensity of high-grade electrostatic field. These studies are relevant in the creation of new devices based on new dispersion, which are not currently used for fuel atomization and combustion devices, in particular based on the electrostatic dispersion. The currently available methods for assessing dispersion are based on the evaluation of the particle diameter, which are formed by dispersing (particle breakage) of the liquid fuel. The views expressed in the course of the study suggest that the dependence of the particle diameter from the electrostatic field can be estimated not only in case of the destruction of the particles (dispersion), but also in case of the formation (growth) of drops during the expiration of the capillary. In order to confirm the provisions the authors developed the installation and technique to study the changes in the dispersion in dependence with the voltage value of high potential electrostatic field. The results of experimental studies are presented and experimental graphics are built for F5 bunker fuel and water-oil emulsions with different concentrations based on it. On the basis of the experimental data processed by correlation analysis method the authors obtained the mathematical model of diameter changes of the particles under the influence of an electrostatic field, which corresponds to the theory of electrostatic dispersion. The developed technique greatly simplifies the determination of the disperse characteristics of liquid fuel in case of electro-static dispersion.

Particle Size Distribution of Micropowder in Jet Milling/Electrostatic Dispersion

Jet milling is an innovative method to prepare micropowder with high efficiency and pureness, while the particles obtained through this way exhibit a prominent agglomeration due to the electrostatic attraction caused by friction of particles during jet milling progress. Recently, we have developed a new method to prepare micropowder by combination of jet milling and electrostatic dispersion. In this paper, both fine powders of calcium carbonate and talc were produced by J/E method, the particle size and its distribution were evaluated by SEM and LPSA as well. The results of our research reveal that the dispersion state of the micropowder thus prepared is influenced by its properties and the combined process is effectiveness in powder pulverization and dispersion.