Search results for " SOLID"

Role of Water During Crystallization of Amorphous Cobalt Phosphate Nanoparticles

2016

The transformation of amorphous precursors into crystalline solids and the associated mechanisms are still poorly understood. We illuminate the formation and reactivity of an amorphous cobalt phosphate hydrate precursor and the role of water for its crystallization process. Amorphous cobalt phosphate hydrate nanoparticles (ACP) with diameters of ∼20 nm were prepared in the absence of additives from aqueous solutions at low concentrations and with short reaction times. To avoid the kinetically controlled transformation of metastable ACP into crystalline Co3(PO4)2 × 8 H2O (CPO) its separation must be fast. The crystallinity of ACP could be controlled through the temperature during precipitati…

Anhydrous Amorphous Calcium Oxalate Nanoparticles from Ionic Liquids: Stable Crystallization Intermediates in the Formation of Whewellite

2015

The mechanisms by which amorphous intermediates transform into crystalline materials are not well understood. To test the viability and the limits of the classical crystallization, new model systems for crystallization are needed. With a view to elucidating the formation of an amorphous precursor and its subsequent crystallization, the crystallization of calcium oxalate, a biomineral widely occurring in plants, is investigated. Amorphous calcium oxalate (ACO) precipitated from an aqueous solution is described as a hydrated metastable phase, as often observed during low-temperature inorganic synthesis and biomineralization. In the presence of water, ACO rapidly transforms into hydrated whewe…

Self-Assembly of Water-Mediated Supramolecular Cationic Archimedean Solids

2013

Understanding the self-assembly of small structural units into large supramolecular assemblies remains one of the great challenges in structural chemistry. We have discovered that tetrahedral supramolecular cages, exhibiting the shapes of Archimedean solids, can be self-assembled by hydrogen bonding interactions using tricationic N-donors (1 or 2) in cooperation with water (W). Single crystal X-ray analysis shows that cage (2)4(W)6, assembled in an aqueous solution of cation 2 and KPF6, consists of four tripodal trications linked by six water monomers and resembles the shape of a truncated tetrahedron. Similarly, cage (1)4(W6)4 spontaneously self-assembles in an aqueous solution of cation 1…

Aging Societies and Intergenerational Solidarity

2010

Due to an increased life expectancy—more people over 65 years old and never before seen numbers of older adults above 85—all countries around the world are nowadays facing rapid demographic changes...

O2 Diffusion in Amorphous SiO2 Nanoparticles Probed by Outgassing

2012

An experimental study of the O2 diffusion process in nanoparticles of amorphous SiO2 in the temperature range from 98 to 157 °C was carried out by Raman and photoluminescence techniques. We studied O2 diffusion in high purity silica nanoparticles with a mean diameter of 14, 20, and 40 nm detecting the outgassing of molecules trapped during the manufacturing. The kinetics of diffusion is well described for all the investigated nanoparticles by the Fick’s equation proving its applicability to nanoscale systems. The diffusion coefficient features an Arrhenius law temperature dependence in the explored temperature range, and the diffusion coefficient values are in good agreement with extrapolat…

Diritti, sicurezza, solidarietà e responsabilità nella protezione delle persone migranti

2018

Le crisi migratorie e l’onda lunga del populismo nei sistemi politici nazionali contro la ricerca dell’equilibrio fra diritti, sicurezza, solidarietà e responsabilità; la Carta dei diritti fondamentali dell’Unione Europea ed il rafforzamento del principio di solidarietà fra Stati; la ricerca dell’equilibrio: il contributo del costituzionalismo. L’esperienza italiana: diritti, solidarietà, responsabilità e sicurezza.

2017

Abstract. Eleven particle samples collected in the polar stratosphere during SOLVE (SAGE III Ozone loss and validation experiment) from January until March 2000 were characterized in detail by high-resolution transmission and scanning electron microscopy (TEM/SEM) combined with energy-dispersive X-ray microanalysis. A total of 4202 particles (TEM  =  3872; SEM  =  330) were analyzed from these samples, which were collected mostly inside the polar vortex in the altitude range between 17.3 and 19.9 km. Particles that were volatile in the microscope beams contained ammonium sulfates and hydrogen sulfates and dominated the samples. Some particles with diameters ranging from 20 to 830 nm were re…

Reactivity of H2S and H2S/H2 Mixture With Molybdenum Oxide Thin Films Epitaxied on CoO (100) : Characterization by Rheed and Auger Spectroscopy

2010

Molybdenum-Cobalt composite oxide films were prepared by the evaporation of molybdenum trioxide on a fresh cleaved CoO (100) surface (Thickness = 10 A). The MoO3-CoO interface has been characterized simultaneously by reflexion high electron diffraction (RHEED) and Auger Electron Spectroscopy (AES). The thin film structure and composition depend on the annealing temperature. After a 300°C treatment, metallic cobalt islands nucleate at the interface thin film - CoO (100) and crystallize with the cubic FCC symmetry. After a 700°C treatment cobalt molybdate (a CoMoO4) islands grow. The metastable crystallites are epitaxied on CoO (100). After a 900°C treatment, the thin film consists of flat tw…

Microstructural evolution of wear-resistant FeCrB and FeCrNiCoB coating alloys during high-energy mechanical attrition

2008

Mechanical milling/attrition provides a convenient scope of simulating the microstructural changes encountered by wear-resistant coating alloys subjected to deformation under high frequency and high-intensity impact loading or accelerated wear condition. In the present study, the microstructural evolution of two commercial coating materials, FeCrB (Armacor M) and FeCrNiCoB (Armacor C), in the course of low- and high-intensity mechanical attrition, was monitored by X-ray diffraction and high-resolution transmission electron microscopy. While low-intensity milling leads to marginal grain refinement but no change in phase-aggregate in FeCrB, similar mechanical attrition causes boride precipita…

<title>Performance problems of electrochromic coatings</title>

2003

The performance is actual problem of electrochromic coatings. The service and shelf life and cycling capacity are main performance characteristics. By solid-state ionics point of view any electrochromic cell based on phenomena with ion insertion - extraction processes is functioning as solid-state rechargeable battery. The main performance characteristics of electrochromic cells are similar. Performance of electrochromic coatings based on amorphous WO3 films and protons conducting electrolytes is limited by reversibility of ion insertion-extraction reactions, which causes degradation of cell components. The migration of water in the cell and hydration together with ion insertion-extraction …