Search results for "medium"

Analysis of the crystallization behaviour of PBT-rich PBT/PET blends under processing conditions

2007

Among the high‐performance polyesters blends PBT/PET blends are expected to exhibit remarkable properties as far as the crystallization behaviour is concerned. The solidification behaviour of a 60/40 w/w PBT/PET blend was studied in a wide range of cooling conditions, according to a Continuous Cooling Transformation (CCT) procedure developed by the authors, aiming to emulate the typical conditions encountered in polymer processing. A set of several samples characterized by an homogeneous structure was prepared by solidification from the melt through spray cooling, and the resulting structure and properties were evaluated by density, Micro Hardness (MH), Wide Angle X‐ray Diffraction (WAXD) m…

Structural, microstructural and impedance spectroscopy study of functional ferroelectric ceramic materials based on barium titanate

2013

The differences between the physical properties of barium titanate BaTiO3 and newly obtained BaHfxTi1-xO3 were identified. These ceramics were prepared by solid-phase reaction from simple oxides and carbonates using the conventional method. The structure and morphology of investigated samples were characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The application of impedance spectroscopy made possible to characterize of these materials in the terms of electrical properties.

Electron-Deficient Pyridylimines: Versatile Building Blocks for Functional Metallosupramolecular Chemistry

2017

Metallosupramolecular systems heavily rely on the correct choice of ligands to obtain materials with desired properties. Engaging this problem, we present three ligand systems and six of their mono- and dinuclear complexes, based on the subcomponent self-assembly approach using electron-deficient pyridylcarbaldehyde building blocks. The properties are examined in solution by NMR and UV-vis spectroscopy and CV measurements as well as in solid state by single crystal X-ray diffraction analysis. Ultimately, the choice of ligands allows for fine-tuning of the electronic properties of the metal centers, complex-to-complex transformations, as well as establishing distinct anion-π-interaction moti…

Differential scanning calorimetry investigation of phase transition in $BaZr_{x}Ti_{1-x}O_{3}$

2009

ABSTRACT Lead-free BaZrxTi1-xO3 (x = 0; 0.025; 0.125) ceramics have been obtained by a conventional method. A single-phase perovskite structure of the ceramics was identified by the X-ray diffraction method. EDS analysis, performed for the individual grains of the tested sample, showed a good homogeneous distribution of all elements throughout the grains. The thermal behaviour of BaZrxTi1-xO3 (x = 0; 0.025; 0.125) ceramics was studied using the Differential Scanning Calorimetry (DSC). Measurements showed the influence of Zr addition on the character of phase transition in the BaTiO3 structure. The results were compared with these ones obtained for pure BaTiO3.

Photocatalytic behaviour of metal-loaded TiO2 aqueous dispersions and films

2007

Abstract Titanium dioxide nanoparticles loaded with Ce, Co, Eu, Sm, W and Yb species were prepared by coprecipitation in mild conditions using TiCl 4 as precursor with the aim to enhance the photocatalytic activity, especially under visible light irradiation. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area (SSA) determination and UV–Vis diffuse reflectance spectroscopy. The photocatalytic activity of the powders of pure and loaded TiO 2 was investigated by employing the photodegradation of 4-nitrophenol as probe reaction in a liquid–solid system. Loading with suitable amounts of W, Co and Sm resulted in a significan…

Density Functional Theory Investigation on the Nucleation of Homo- and Heteronuclear Metal Clusters on Defective Graphene

2016

Nucleation of homo- (Ni, Pd, Re, Pt) and heterometallic (Ni–Pd, Re–Pt) clusters on monovacancy sites of a graphene sheet has been investigated by means of periodic density functional theory calculations. It is shown that a vacant site in graphene is an effective nucleation center for both the monometallic and bimetallic clusters, whose characteristics are described in terms of structural distortions, nucleation energetics, affinities between different metal atoms, metal–carbon interactions, and ease of diffusion of metal atoms on graphene.

2020

Epoxy resin plays a key role in composite matrices and DGEBA is the major precursor used. With the aim of favouring the use of bio resources, epoxy resins can be prepared from lignin. In particular, diglycidyl ether of isoeugenol derivatives are good candidates for the replacement of DGEBA. This article presents an effective and eco-friendly way to prepare epoxy resin derived from isoeugenol (BioIgenox), making its upscale possible. BioIgenox has been totally characterized by NMR, FTIR, MS and elemental analyses. Curing of BioIgenox and camphoric anhydride with varying epoxide function/anhydride molar ratios has allowed determining an optimum ratio near 1/0.9 based on DMA and DSC analyses a…

New structural motifs in Mn cluster chemistry from the ketone/gem-diol and bis(gem-diol) forms of 2,6-di-(2-pyridylcarbonyl)pyridine: {MnII4MnIII2} a…

2016

The employment of the tripyridyl/diketone ligand 2,6-di-(2-pyridylcarbonyl)pyridine [(py)CO(py)CO(py)], in conjunction with azides (N3−), in Mn cluster chemistry has afforded the mixed-valence (II/III) complexes [MnII4MnIII2(N3)6Cl4(L1)2(DMF)4] (1) and [MnII4MnIII6O2(N3)12(L1)2(L2H)2(DMF)6] (2) in good yields. The resulting ligands L12− and L2H3− are the dianion and trianion of the ketone/gem-diol (L1H2) and bis(gem-diol) (L2H4) forms of (py)CO(py)CO(py), respectively, as derived from the metal-assisted hydrolysis of the parent dicarbonyl organic compound. Under the same synthetic conditions (i.e., reaction solvents, temperature and stirring time), the chemical identity of the two complexes…

Fluid reservoirs in the crust and mechanical coupling between the upper and lower crust

2004

An important observation associated with seismic activity on the Nagamachi-Rifu Fault is the existence of tabular, fluid rich zones at mid-crustal levels. These zones resemble the “bright spots” seen in many seismic images of the crust worldwide. The aim of this paper is to develop the mechanical foundations for the formation of such zones. To do so requires an understanding of the distribution of pore fluid pressure in a deforming crust. In a hydrostatically stressed porous material, the pore fluid pressure should equal the mean stress in order to keep the pores from collapsing. Past discussions of this subject imply very high pore fluid pressures, two to three times lithostatic. Considera…

Synthesis, X‐ray Structure, Thermal and Magnetic Behavior of [(bipy) 2 Ni 2 (μ‐Cl) 2 Cl 2 (H 2 O) 2 ]: The First Neutral Ferromagnetically Coupled Si…

2007

NiCl2·6H2O and 2,2′-bipyridine (bipy) (1:1) were allowed to react under ambient conditions in dimethyl sulfoxide in the presence of acetylacetone (Hacac). The resulting green solution was concentrated in vacuo, and a green solid was isolated by precipitation with cold acetone. X-ray quality crystals of [(bipy)2Ni2(μ-Cl)2(Cl)2(H2O)2] (1) were grown by subsequent vapor/liquid diffusion of acetonitrile into a methanolic solution for one week. The structure of 1 consists of a dimeric nickel system with each metal atom in an octahedral geometry. Both equatorial bridging and axial chlorine atoms are present in this neutral species. The nickel–nickel distance (3.441 A) is the shortest reported to …