Influence Of Ionic Charge Research Articles

The GO composite coatings for enhancing interfacial interaction performance and desensitization of CL-20

Although CL-20 is one of the most widely used high-explosives, the issue of its high sensibility and interfacial interaction with coating material in composite explosives have not yet been well understood. Herein, the electrostatic self-assembly capability of a graphene oxide (GO) aqueous solution was utilized to desensitize CL-20 and enhance its interfacial interaction by preparing a CL-20@GO@desensitizer composite, which was prepared by the “one-pot” water suspension method. It was found that the CL-20@GO composite exhibited a compact GO cladding layer and demonstrated exceptional safety characteristics. On this basis, the structure and performance of three CL-20@GO@densitizer composites were characterized by SEM, XPS, ZETA, DSC, XRD, and mechanical sensitivity. The morphology of composites showed that GO@microcrystalline wax (MW) was evenly coated on the surface of CL-20 under the influence of ionic charge and -OH bonding. The surface analysis results indicated that three types of GO@desensitizer films possessed exceptional coating effectiveness. The thermal analyses results suggested that the CL-20@GO@ethylene propylene diene monomer (EPDM) endowed Ea of composite up to 351.43 kJ/mol, while, the Ea of CL-20@GO, CL-20@GO@MW and CL-20@GO@MW + EPDM were only 184.36 kJ/mol, 186.21 kJ/mol and 258.79 kJ/mol, respectively. Besides, the XRD results confirmed that the three films had not caused a transformation of the CL-20 crystal phase, which afforded process safety support for the further application of this composite particle. Due to the high thermal conductivity of desensitizer-film, the composite showed a advantage in mechanical sensitivity, which can reach to a level of 252 N and 10 J. These findings can provide a reference for enhancing surface performance and desensitization of CL-20.

Micromodulation of dual-shell CL-20/desensitizer interface based on in-situ assembly of tea polyphenols

Although the research on CL-20 crystals has reached a high level, the property of the explosive-desensitizer interface is a key concern for composite explosive applications. Herein, inspired by super adhesion performance on cup, the in-situ assembly ability of tea polyphenol (TP) was utilized to enhance the surface performance and desensitize CL-20. The five kinds of core-dual-shell composites were fabricated by the “one-pot” water suspension method under the influence of ionic charge, -OH bonding, and the structure like suction cup of ivy. They were characterized by SEM, XPS, TG-DSC, XRD, and mechanical sensitivity device. The morphology and surface analysis results indicated that TP and desensitizer were evenly coated on the surface of CL-20, forming a core-dual-shell structure. This provided a great structural contribution to its security. The thermal analysis results suggested that TP/microcrystalline wax (MW) was endowed with thermal decomposition activation energy (Ea) of CL-20 from 190.92 kJ/mol up to 200.99 kJ/mol. While, the Ea of CL-20/TP, CL-20/TP/GO, CL-20/TP/TPU, and CL-20/TP/TPU-PDA were only 189.33 kJ/mol, 190.61 kJ/mol, 199.77 kJ/mol, and 184.75 kJ/mol, respectively. Meanwhile, the TP/GO film reduced Tp0 of CL-20 from 218.15 ℃ to 208.21 ℃ and Tb from 220.27 ℃ to 210.14 ℃, respectively. Besides, the XRD results confirmed that the five films had not caused a transformation of the ε-CL-20 crystal phase, which afforded process safety support for the further application of these composite particles. Due to the properties of MW and the advantages of dual-shell composite structural, the TP/MW film brought mechanical sensitivity of CL-20 from 60 N and 3.5 J to 336 N and 8.97 J, closing to the level of PBXs with 95% LLM-105% and 5% ternary composite (11 J). These safety parameters indicate materiel of moderate sensitivity that possibly can be handled in accordance with standard procedures. Moreover, the particle coated with TP/TPU-PDA possessed better free-running property. These findings can provide reference for the large-scale application of CL-20.

Influence of Ionic Charges on the Bilayers of Lamellar Phases

The influence of ionic charges on the mesophases in the ternary system of C(12-16)E(6) (LA 070), ethylhexylglycerid (EHG), and water was studied. The charge was introduced by adding the ionic surfactant SDS (sodium dodecyl sulfate). The single lamellar phase (5 wt % LA 070 and 240 mM EHG in water) yields a bluish homogeneous solution. With the addition of SDS, the samples become more and more clear. Rheology measurements indicate that increased charge density increases the storage modulus G', and the lamellar phases show typical behavior of a viscoelastic fluid with a yield stress at higher SDS concentration. SAXS measurements show that the interlamellar distance D decreases with SDS concentration. The addition of ionic surfactants suppresses the Helfrich undulations, flattens the bilayers, and decreases interbilayer spacing due to electrostatic repulsions of the ionic surfactant head groups. Furthermore, the L(alpha) phase transforms into vesicle phases as the SDS concentration is increased. Second, it is shown that with added NaCl electrolyte the phase with charged surfactant behaves again in the same way as the initial uncharged system. The addition of salt screens the electrostatic interaction, which leads to a higher flexibility of the bilayers and a decrease of the storage modulus G'. Theoretical calculations show that the shear moduli of the L(alpha) phases are much smaller than the osmotic pressure of the systems. Several models are proposed for the explanation of the shear moduli. The model due to Lekkerkerker for the electric contribution of the bending constant of the bilayer seems to yield good results for the transition to vesicles.

Influence of ionic charge and dipole fluctuations on the lattice dynamics, dielectric properties, and infrared response of La2CuO4

We generalize our recently proposed microscopic formulation of the electronic density response and screening and apply it to lattice dynamics and, also to the dielectric properties of the high-temperature superconductors (HTSC's). Our previously developed method of screening in the HTSC in terms of ionic charge fluctuations (CF's) is extended by including additional dipole fluctuations as possible electronic polarization processes. The latter prove to be important in the HTSC, especially for the ions in the ionic layers. On the other hand, CF's are the dominating polarization process in the CuO planes. In particular, we have predicted in the past strong coupling via CF's of the high-frequency copper-oxygen bond-stretching modes in the HTSC. These modes are thought now to cause a kink in the electronic dispersion observed by photoemission. Our model calculations in this paper deal with both the metallic as well as the insulating phase of ${\mathrm{La}}_{2}{\mathrm{CuO}}_{4}.$ Complete phonon dispersion curves are calculated for both phases and specific modes discussed controversially in the literature are studied in detail. Finally, the macroscopic high-frequency and static dielectric constants, transverse effective charges, and oscillator strengths of the infrared-active vibrations are investigated.

The influence of ionic charges on the structural and dynamical behavior of O/W microemulsion droplets

AbstractAn O/W microemulsion system has been investigated where the droplet size can be controlled via the concentration of cosurfactant (1‐hexanol). In that system the charge density of the droplets was varied by substitution of the original nonionic surfactant by a cationic surfactant. SANS measurements showed that the droplet radii are unaffected by the charging process, whereas the polydispersity decreases with increasing charge density. SANS and also static light scattering experiments are well described by a simple electrostatic model, which renders this droplet system a good model system. In contrast to that the diffusion coefficient shows a somewhat more complicated behavior. It increases strongly with rising ionic content but goes through a maximum around 3 mol% ionic surfactant and then decreases again. The magnitude of the increase and the position of the maximum are well described by theory, whereas the steepness of the decrease at still higher ionic surfactant content is not accounted for.

On the Structure and Dynamic Properties of Aqueous Solutions: Molecular Dynamics Simulation of Cl−and Cl2-in Water

Abstract Molecular dynamics simulations of Cl− and Cl2− in water with four slightly different versions of the simple point charge (SPC) potential have been carried out. Both structural and dynamic properties including reorientational and residence times, velocity autocorrelation functions, self diffusion coefficients and spectral densities have been analyzed. The influence of ionic charge as well as flexibility, molecular dipole moment, charge distribution and molecular geometry of water on the properties of ions and water molecules in the hydration shell is discussed.

The Lyotropic Mesophases in Dilute Surfactant Mixtures of Tetradecyldimethylaminoxide, Tetradecyltrimethylammonium Bromide, and Hexanol: The Influence of Ionic Charge on the Mesophases

The influence of ionic charges on the mesophases in the ternary phase diagram of tetradecyldimethylaminoxide (C 14DMAO), hexanol, and water was studied. The charges were introduced by replacing C 14DMAO by the cationic surfactant tetradecyltrimethylammonium bromide (C 14TMAB). The phase diagram becomes much simpler by this substitution. The L 1- , L 3-, and L 3-phases which had previously been observed for the uncharged system are very sensitive to the charges and disappear completely with increased mole fraction of C 14TMAB ( Xc > 0.2). Furthermore, the L α1 - and the L αh-phases merge into a single L α-phase which has properties similar to those of the L α1-phase in the uncharged system. The most prominent feature of the charged L α-phase is its theological yield stress value. With increasing Xc the phase boundaries of the L 1- and the L α-phase are shifted to a higher mole fraction of alcohol ( Xa). The two phase regions ( L 1 + L α) widen with increasing X c. Samples in this two phase region separate easily into two phases. The properties of the different phases were determined and characterized by conductivity and theological measurement and by polarization microscopy. FF-TEM micrographs show that the charged L α-phase consists over the whole existence region of single and multilamellar vesicles. The vesicles at the lower phase boundary (low Xa-values) seem to have defects which disappear with increasing Xa-values. Finally, it is shown that with the addition of excess salt the phase diagram with the charged surfactant behaves again in the same way as the uncharged system.

Influence of Ionic Charge on Diffusion in the Surface Layer of Magnesia

The diffusion of 57Co isotope on the MgO (100) surface was investigated by the edge‐source method. The surface diffusion parameter, αDsδ, where α is the segregation factor, Ds the surface diffusion coefficient, and δ the thickness of the high‐diffusivity layer, was determined over the temperature region 750° to 1250°C. An Arrhenius plot shows a break at ∼1100°C. Below this temperature ionic or localized transport predominates and above it nonlocalized transport seems to predominate. The divalent Co ion diffuses faster than the trivalent Cr ion in the surface layer. The apparent activation energies for the localized surface diffusion of 57Co and 59Cr are 59±12 and 110±12 kj/mol, respectively.

Schwingungspektren und Kraftkonstanten von Phosphorverbindungen

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