Search results for "Crystallinity"
showing 10 items of 248 documents
Some factors affecting the removal of lead(II) ions from aqueous solution by porous hydroxyapatite: relationships between surface and adsorption prop…
2006
A porous hydroxyapatite (p-HAp) was prepared and employed for the removal of lead(II) ions at different concentrations from aqueous solution to determine the adsorption properties of p-HAp and compare them with those of a commercial hydroxyapatite (CAp) sample. The kinetic data obtained indicated that the adsorption performances of the adsorbents depended both on their specific surface area and crystallinity. Complexation of the Pb(II) ion on the adsorbent surface favoured the dissolution of hydroxyapatites characterized by a Ca/Pb molar ratio in the 0.85–1.5 range. The maximum adsorption capacity of p-Hap for Pb(II) ions at 30 ± 2°C was 2.30 mmol/g relative to 1.38 mmol/g for the commercia…
Structure and characteristics of laser crystallized thin amorphous Si films
2011
Abstract Pure amorphous Si thin films deposited on oxidized crystalline Si surface (111) were crystallized by picosecond UV laser pulses. The Raman scattering spectra show that pulse energy of 330 mJ/cm2 is enough to fully crystallize Si film and further increase of the energy does not improve crystallinity. A large grained polycrystalline Si was obtained as revealed by surface analysis. A significant increase in carrier mobility was observed after laser crystallization.
The Ultimate Fate of Supercooled Liquids
2010
In recent years it has become widely accepted that a dynamical length scale {\xi}_{\alpha} plays an important role in supercooled liquids near the glass transition. We examine the implications of the interplay between the growing {\xi}_{\alpha} and the size of the crystal nucleus, {\xi}_M, which shrinks on cooling. We argue that at low temperatures where {\xi}_{\alpha} > {\xi}_M a new crystallization mechanism emerges enabling rapid development of a large scale web of sparsely connected crystallinity. Though we predict this web percolates the system at too low a temperature to be easily seen in the laboratory, there are noticeable residual effects near the glass transition that can account …
Stimuli-responsive hybrid materials: breathing in magnetic layered double hydroxides induced by a thermoresponsive molecule
2014
[EN] A hybrid magnetic multilayer material of micrometric size, with highly crystalline hexagonal crystals consisting of CoAl-LDH ferromagnetic layers intercalated with thermoresponsive 4-(4-anilinophenylazo)benzenesulfonate (AO5) molecules diluted (ratio 9 : 1) with a flexible sodium dodecylsulphate (SDS) surfactant has been obtained. The resulting material exhibits thermochromism attributable to the isomerization between the azo (prevalent at room temperature) and the hydrazone (favoured at higher temperatures) tautomers, leading to a thermomechanical response. In fact, these crystals exhibited thermally induced motion triggering remarkable changes in the crystal morphology and volume. In…
Concentration-dependent anti-/pro-oxidant activity of natural phenolic compounds in bio-polyesters
2017
Abstract In this work, the potential of several naturally occurring phenolic compounds, such as Ferulic Acid (FA), Vanillic Acid (VA), Vitamin E (VE) and Quercetin (Q), as stabilizers against the photo-oxidative degradation of Polylactic acid (PLA) has been assessed. Specifically, PLA-based films containing different amounts of considered stabilizers have been formulated and their photo-stability under UVB exposure has been evaluated. The preliminary characterization of the formulated films shows that all used stabilizers exert plasticizing action, as probed by rheological analysis, due to their low molecular weight. Moreover, no significant modification of the PLA crystallinity has been no…
Growth of glass-embedded Cu nanoparticles: A low-frequency Raman scattering study
2012
International audience; Several populations of Cu spherical nanoparticles grown in a silicate glass at different temperatures with respect to the glass transition temperature were studied using high-resolution, low-frequency Raman scattering and optical absorption. The analysis of the spectra shows that the annealing of the doped glass at temperatures close to T-g leads to the formation of metallic copper nanoparticles with high crystallinity, whereas lower-temperature and higher-temperature annealings result in the formation of poorer nanoparticle assemblies in terms of size distribution and/or nanocrystallinity. It is also shown that in the case where the optical data do not unambiguously…
Atomic layer deposition and characterization of biocompatible hydroxyapatite thin films
2009
Abstract Atomic layer deposition (ALD) was used to produce hydroxyapatite from Ca(thd) 2 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionato) and (CH 3 O) 3 PO onto Si(100) and Corning (0211). Film crystallinity, stoichiometry, possible impurities and surface morphology were determined. The as-deposited films contained significant amounts of carbonate impurities however, annealing at moist N 2 flow reduced the carbonate content even at 400 °C. The as-deposited Ca–P–O films were amorphous but rapid thermal annealing promoted the formation of the hydroxyapatite phase. Mouse MC 3T3-E1 cells were used for the cell culture experiments. According to the bioactivity studies cell proliferation was enhanc…
Low-temperature atomic layer deposition of ZnO thin films: Control of crystallinity and orientation
2011
Abstract Low-temperature atomic layer deposition (ALD) processes are intensely looked for to extend the usability of the technique to applications where sensitive substrates such as polymers or biological materials need to be coated by high-quality thin films. A preferred film orientation, on the other hand, is often required to enhance the desired film properties. Here we demonstrate that smooth, crystalline ZnO thin films can be deposited from diethylzinc and water by ALD even at room temperature. The depositions were carried out on Si(100) substrates in the temperature range from 23 to 140 °C. Highly c-axis-oriented films were realized at temperatures below ~ 80 °C. The film crystallinit…
Structure and properties of polyethyleneterephthalate crystallized by annealing in the highly oriented state
1976
The structure of polyethyleneterephthalate bristles drawn about five times in the amorphous state and subsequently crystallized at temperatures between 100 and 260‡ C has been studied by means of small-angle X-ray scattering. In addition density, heat of fusion and wide-angle scattering behaviour were measured. For comparison, similar experiments were carried out with undrawn samples. The results showed that the degree of crystallinity of PET cannot be calculated from density data on the basis of a simple two-phase model, since the effective densitiesρc* andρa* of the crystalline and amorphous regions depend strongly on crystallization and drawing conditions. With rising crystallization tem…
Effect of Nanodiamonds on Structure and Durability of Polyethylene Oxide-Based Nanocomposites
2016
Polymer-based nanocomposites containing nanodiamonds (NDs) are attractive multifunctional materials with a growing range of applications. In this work, in the frame of developing completely biocompatible systems, nanocomposites based on polyethylene oxide (PEO) and different amount of NDs have been formulated through melt mixing and fully characterized. In particular, the reinforcement effect of NDs in PEO has been probed through tensile tests, and the rheological response of PEO-based nanocomposites as a function of the nanoparticles amount has been investigated and discussed. The obtained results show that the presence of well-distributed NDs strengthens the mechanical performance of the …