Search results for "Ceramic"

Time–carbonyl groups equivalence in photo-oxidative aging of virgin/recycled polymer blends

2004

AbstractThe photo-oxidation behaviour of polymers is strongly dependent on the initial amount of carbonyl groups along the chains. The growing use of recycled post-consumer polymers coming from products used outdoors and then photo-oxidised, both pure and blended with the same virgin polymer, gives rise to an unpredictable behaviour of weathering resistance of products made with these materials. The present work shows that the carbonyl group–exposure time curves can be shifted along the time axis to give a single generalised master plot. It is then possible to predict the formation of the new carbonyl groups by knowing only the initial amount of the same carbonyl groups. The same shift fact…

Corrigendum to “Biomolecule-corona formation confers resistance of bacteria to nanoparticle-induced killing: Implications for the design of improved …

2020

A giant hybrid organic-inorganic octahedron from a narrow rim carboxylate calixarene.

2020

Here we discovered an unprecedented giant octahedral coordination compound bearing 16 Zn2+, 12 Na+, 8 O2-, 4 OH-, 13 H2O and 6 L4- ligands [L4- = fully deprotonated tetra(carboxymethoxy)calix[4]arene]. Its structure was elucidated by single-crystal X-ray diffraction, wavelength-dispersive X-ray spectroscopy and MALDI-TOF mass spectrometry. This compound, Zn8Na6L6⊃Zn8Na6O8(OH)4(H2O)13 (external⊃internal), has eight tetrahedral zinc ions forming the coordination vertices of an outermost cube where carboxylate groups from the sodium calixarenes are anchored. Its core consists of eight Zn2+, six Na+, eight O2-, and four OH- distributed over three layers, besides thirteen coordinated H2O molecul…

Polyethylene composites filled with n‐alkyl‐functionalized siloxane‐silsesquioxane resins and sol‐gel silicas

2019

High‐density polyethylene (HDPE) composites filled with silicon‐based fillers were prepared by melt blending. The use of non‐functionalized and n‐octyl‐functionalized siloxane‐silsesquioxane resins and the sol‐gel silicas as fillers allowed us to evaluate the influence of functionalization of the fillers on the properties of the composites. The melting and crystallization temperatures of the composites were found to be only slightly affected by the addition of the silicon‐based fillers. In turn, the crystallization degree values were increased, in particular for the materials containing non‐functionalized fillers. The free‐volume properties of the composites did not change significantly in …

Some Aspects of the Influence of Particle Size on Properties and Behaviour of a Dielectric Material : Example of Barium Titanate

1989

Anybody agrees with the idea that particle size plays an important role in the behaviour of a polycrystalline material but very few studies are giving precise information about this role. In this paper some experimental results are presented succintly to illustrate the importance of this physico-chemical factor. They are related to barium titanate, the main component of the dielectric material in the type II ceramic capacitors.

Morphological Characterisation of Bacterial Cellulose-Starch Nanocomposites

2008

Acetobacter sp. growing medium was modified in order to produce bacterial cellulose (BC) nanocomposites using a bottom-up technique that allowed starch to be introduced into the cellulose network. The BC-starch mats were hot-pressed to obtain nanocomposites sheets. Morphological characterisation was carried out using Atomic Force Microscopy and Environmental Scanning Electron Microscopy. The images obtained from microscopy were then processed using image analysis. Network properties, such as mesh size and fibre orientation were characterised. Fracture surfaces of these new nanocomposites were analysed.

Synthesis of chemisorbed imidazolium and phosphonium cations by reaction of ionic liquid precursors with silica.

2010

The reaction of four different basic ionic liquid precursors with Aerosil®300 is presented. Chemisorbed imidazolium and phosphonium cations, with silanolate anions as part of the silicatic support, were obtained and investigated with various solid state NMR techniques.

Recognition and sensing of fluoride anion.

2009

Fluoride anion recognition is attracting a mounting interest in the scientific community due to its duplicitous nature. It is a useful chemical for many industrial applications, and it has been used in human diet, but, recently it has been accused for several human pathologies. Here we describe the ample panorama of different approaches the chemists world-wide have employed to face the challenge of fluoride binding, and we outline some of the research which in our view can contribute to the development of this field, especially when fluoride binding has to be achieved in highly competitive protic solvents and water.

An efficient synthesis of new fluorinated uracil derivativesElectronic supplementary information (ESI) available: general procedures for the preparat…

2003

A series of potentially biologically active fluorinated uracil derivatives has been prepared in three steps from oxazolines and fluorinated nitriles with good chemical yields.

Uranium( iv ) cyclobutadienyl sandwich compounds: synthesis, structure and chemical bonding

2019

The 1 : 1 reactions of uranium(IV) tetrakis(borohydride) with the sodium and potassium salts of the cyclobutadienyl anion [C4(SiMe3)4]2− (Cb′′′′) produce the half-sandwich complexes [Na(12-crown-4)2][U(η4-Cb′′′′)(BH4)3] and [U(η4-Cb′′′′)(μ-BH4)3{K(THF)2}]2. In the 1 : 2 reaction of U(BH4)4 with Na2Cb′′′′, formation of [U(η4-Cb′′′′)(η3-C4H(SiMe3)3-κ-(CH2SiMe2)(BH4))]− reveals that a Cb′′′′ ligand undergoes an intramolecular deprotonation, resulting in an allyl/tuck-in bonding mode. A computational study reveals that the uranium–Cb′′′′ bonding has an appreciable covalent component with contributions from the uranium 5f and 6d orbitals. peerReviewed