Composite Films of HDPE with SiO2 and ZrO2 Nanoparticles: The Structure and Interfacial Effects.

Herein, we investigated the influence of two types of nanoparticle fillers, i.e., amorphous SiO2 and crystalline ZrO2, on the structural properties of their nanocomposites with high-density polyethylene (HDPE). The composite films were prepared by melt-blending with a filler content that varied from 1% to 20% v/v. The composites were characterized by small- and wide-angle x-ray scattering (SAXS and WAXS), small-angle neutron scattering (SANS), Raman spectroscopy, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). For both fillers, the nanoaggregates were evenly distributed in the polymer matrix and their initial state in the powders determined their surface roughness and fractal character. In the case of the nano-ZrO2 filler, the lamellar thickness and crystallinity degree remain unchanged over a broad range of filler concentrations. SANS and SEM investigation showed poor interfacial adhesion and the presence of voids in the interfacial region. Temperature-programmed SANS investigations showed that at elevated temperatures, these voids become filled due to the flipping motions of polymer chains. The effect was accompanied by a partial aggregation of the filler. For nano-SiO2 filler, the lamellar thickness and the degree of crystallinity increased with increasing the filler loading. SAXS measurements show that the ordering of the lamellae is disrupted even at a filler content of only a few percent. SEM images confirmed good interfacial adhesion and integrity of the SiO2/HDPE composite. This markedly different impact of both fillers on the composite structure is discussed in terms of nanoparticle surface properties and their affinity to the HDPE matrix.

Structural, Thermal, and Vibrational Properties of N,N-Dimethylglycine-Chloranilic Acid-A New Co-Crystal Based on an Aliphatic Amino Acid.

The new complex of N,N-Dimethylglycine (DMG) with chloranilic acid (CLA) was synthesized and examined for thermal, structural, and dynamical properties. The structure of the reaction product between DMG and CLA was investigated in a deuterated dimethyl sulfoxide (DMSO-d6) solution and in the solid state by Nuclear Magnetic Resonance (NMR) (Cross Polarization Magic Angle Spinning-CPMAS NMR). The formation of the 1:1 complex of CLA and DMG in the DMSO solution was also confirmed by diffusion measurement. X-ray single crystal diffraction results revealed that the N,N-dimethylglycine-chloranilic acid (DMG+-CLA-) complex crystallizes in the centrosymmetric triclinic P-1 space group. The X-ray diffraction and NMR spectroscopy show the presence of the protonated form of N,N-dimethylglycine and the deprotonated form of chloranilic acid molecules. The vibrational properties of the co-crystal were investigated by the use of neutron (INS), infrared (IR), and Raman (RS) spectroscopies, as well as the density functional theory (DFT) with periodic boundary conditions. From the band shape analysis of the N-CH3 bending vibration, we can conclude that the CH3 groups perform fast (τR ≈ 10-11 to 10‒13 s) reorientational motions down to a temperature of 140 K, with activation energy at ca. 6.7 kJ mol-1. X-ray diffraction and IR investigations confirm the presence of a strong N+-H···O- hydrogen bond in the studied co-crystal.

Phase transition tuning by Fe(iii)/Co(iii) substitution in switchable cyano-bridged perovskites: (C3H5N2)2[KFexCo1-x(CN)6].

The single-crystals of mixed (C3H5N2)2[KFexCo1-x(CN)6] crystals, with different ratios of x = 0, 0.29, 0.42, 0.51, 0.63, 0.70, 0.85, 1, have been grown from aqueous solutions. The thermal stability of the crystals has been determined using both DTA and TGA analysis. DSC has revealed sequences of structural phase transitions (PTs). We have found four solid phases for the crystals with concentrations x < 0.6 and three phases above these concentrations. The Fe(iii) concentration has been estimated using the SEM technique. We have found the linear relationship of Tcversus the molar concentration of Fe(iii) for the IV → III PT. Based on the obtained results, a phase diagram has been constructed. The mechanism of the structural PTs has been discussed based on the results of dielectric relaxation, NIR, IR and Raman spectroscopyand X-ray measurements. Dielectric switching has been observed for all analysed mixed-crystals. All crystals exhibit ferroelastic properties.

Ruthenium as an important element in nuclear energy and cancer treatment.

Ruthenium belongs to the platinum group metals (PGMs) which include palladium (Pd), platinum (Pt), osmium (Os), iridium (Ir) and rhodium (Rh). Radioactive isotopes of ruthenium are important elements related to the nuclear field. Ruthenium is one of the fission products in nuclear reactors and one of the troublesome nuclide in reprocessing process of the spent nuclear fuel (PUREX). The increased concentration of ruthenium-106 in the environment can be the result of accidents in nuclear power plants, spent nuclear fuel processing plants, or of nuclear tests. On the other hand, radioisotope of ruthenium Ru-106 is a drug that is successfully used in brachytherapy. In this paper we describe both sides of this element.

The structure, methyl rotation reflected in inelastic and quasielastic neutron scattering and vibrational spectra of 1,2,3,5-tetramethoxybenzene and its 2:1 complex with 1,2,4,5-tetracyanobenzene.

X-ray diffraction studies show that molecules of the 1,2,3,5-tetramethoxybenzene (TMOB)(2) x 1,2,4,5-tetracyanobenzene complex form ...CCDCCDCC... columns with the short distances between molecular planes of C and D molecules equal to 3.186 A. The vibrational spectra recorded by using the inelastic neutron scattering, Raman, IR, and quasielastic neutron scattering (QENS) techniques aided by density functional theory calculations for the isolated molecules and the crystalline state enabled all four inequivalent librational modes, ascribed to the methoxy groups, to be analyzed. A rather good consistency was found between the experimental frequencies and those calculated for the crystal. The consistency was also achieved between the experimental structure of molecules and the theoretically reproduced one. A close similarity of the structures of the TMOB molecule isolated and in the complex is taken as a sign of dominating intramolecular interaction. The QENS spectra contain three Lorentzians of relative intensities of 1:1:2. Thus the two most strongly hindered of the four inequivalent methoxy groups in the crystalline lattice are characterized by rather similar barrier heights in good agreement with the packing analysis.

Elastic, quasielastic, and inelastic neutron-scattering studies on the charge-transfer hexamethylbenzene-tetracyanoquinodimethane complex.

The 1:1 hexamethylbenzene (HMB)-tetracyanoquinodimethane (TCNQ) complex shows a first-order phase transition at 230/218 K (heating/cooling) with no change of the space group. The neutron-diffraction studies reveal that this transition is related to a freezing of the rotation of methyl groups. The results for 100 K enabled precise determination of configuration of HMB.TCNQ complexes. The planes of HMB and TCNQ molecules from small angle (6 degrees) so that the dicyanomethylene group approaches the HMB molecule to a distance of 3.34 angstroms. The conformation of methyl groups was exactly determined. The quasielastic neutron-scattering spectra can be interpreted in terms of 120 degrees jumps with different activation barrier in low- and high-temperature phases, equal to 3.7 and 1.8 kJ/mol, respectively. These values are lower than that for neat HMB (6 kJ/mol). The conclusion can be drawn that the methyl groups can reorient more freely in the complex. This conclusion is in agreement with the results of inelastic neutron-scattering studies of low-frequency modes assigned to torsional vibrations of methyl groups. These frequencies are lower than those for neat HMB. The analyzed increase of frequencies of these modes as compared with free molecules can be interpreted as due to formation of unconventional C-H...Y hydrogen bonds which are more pronounced in crystals of neat HMB than in those of HMB.TCNQ. The low-frequency librational modes can be treated as a sensitive measure of unconventional hydrogen bonds formed by the CH3 groups.