Search results for "Crystallization"
showing 10 items of 774 documents
Magnetostructural relationships in polymorphic ethylmalonate-containing copper(ii) coordination polymers
2018
Three ethylmalonate-containing copper(II) chiral complexes of the formula {[Cu(H2O)4][Cu(Etmal)2(H2O)]}n (1), [Cu(Etmal)(H2O)]n (2) and {[Cu(Etmal)(H2O)]·H2O}n (3) (H2Etmal = ethylmalonic acid) were obtained by reacting copper(II) nitrate trihydrate, ethylmalonic acid and sodium carbonate in water. Compound 1 is a chiral zigzag chain with regular alternation of [Cu(Etmal)2(H2O)]2− and [Cu(H2O)4]2+ units, the former acting as bis-monodentate ligands toward the latter ones through the two carboxylate groups. The chirality of 1 is a result of the [Cu(Etmal)2(H2O)]2− fragment whose five-coordinate copper(II) surrounding exhibits the Δ or Λ conformation within the Δ or Λ-crystals. The structure …
On the structural aspects of solid solutions of enantiomers: an intriguing case study of enantiomer recognition in the solid state
2018
Structural aspects of solid solutions of enantiomers have been considered and the corresponding definitions of type 1 and type 2 solid solutions have been revised based on the available structures reported in the literature. Examples of both types are presented indicating that (e.g., type 1 solid solutions) there is a straightforward relationship between the particular structural aspects and the enantiomer miscibility limits in the solid state. Furthermore, enantiomer recognition in a type 2 solid solution formed by the enantiomers of a pharmaceutically active ingredient, pimobendan, has been studied in more detail. It was found that upon rapid crystallization from a solution a structure po…
The CRATI project: New insights on the consolidation of saltweathered stone and the case study of San Domenico Church in Cosenza (South Calabria, Ita…
2019
This paper presents the results of a laboratory experimentation carried out on stone materials in the framework of the CRATI project (Knowledge and Restoration through Advanced Integrated Technologies) aimed at testing new products with consolidating properties by means of an integrated methodological approach. After the preliminary characterization of stone materials collected in the pilot site, the second stage of the activities within the project were focused on the formulation and testing of products for the conservation of the same materials against decay, especially salt crystallization, one of the most aggressive and common degrading processes. The San Domenico Church, located in the…
Ultrasonic cavitation induced water in vegetable oil emulsion droplets--a simple and easy technique to synthesize manganese zinc ferrite nanocrystals…
2012
In the present investigation, synthesis of manganese zinc ferrite (Mn(0.5)Zn(0.5)Fe(2)O(4)) nanoparticles with narrow size distribution have been prepared using ultrasound assisted emulsion (consisting of rapeseed oil as an oil phase and aqueous solution of Mn(2+), Zn(2+) and Fe(2+) acetates) and evaporation processes. The as-prepared ferrite was nanocrystalline. In order to remove the small amount of oil present on the surface of the ferrite, it was subjected to heat treatment at 300 °C for 3h. Both the as-prepared and heat treated ferrites have been characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), TGA/DTA, transmission electron microscopy (TEM) and energy dispersion X…
Positron annihilation probing of crystallization effects in TAS-235 glass affected by Ga additions
2014
Abstract Crystallization effects in Te20As30Se50 glass known also as TAS-235 affected by Ga additions to Ga2Te20As28Se50 and Ga5Te20As25Se50 compositions are probed with positron annihilation spectroscopy in the measuring modes exploring positron lifetimes and Doppler broadening of annihilation line. Occurring of cubic-phase Ga2Se3 droplets with character nanoscale sizes in partially-crystallized Ga2Te20As28Se50 alloy is shown to be associated with agglomeration of intrinsic free-volume voids, this process being enhanced over microcrystalline scale in Ga5Te20As25Se50 alloy. Crystallization changes in the void structure of TAS-235 glass are considered in terms of free-volume evolution under …
Effect of Ni content on the structure and hydrogenation property of mechanically alloyed TiMgNix ternary alloys
2017
Abstract In this study, TiMgNix samples (x = 0.2, 0.4, 0.6, 0.8, 1) have been prepared by mechanical alloying using a planetary high-energy ball mill. The structural transformations were characterized by XRD and indicated that all the as-milled TiMgNix alloys consist of mixtures of crystalline Mg and amorphous Ti-Ni-(Mg) phase. TEM analyses also show that nanocrystallites and amorphous phases coexist in the as-milled TiMgNi alloy. Electrochemical test shows that the TiMgNi composition yields the highest discharge capacity. The discharge capacities and activation properties of TiMgNix alloys linearly increase with increasing Ni content. The MgTiNi0.8 composition boasts the best cycling prope…
SURFACE AND VOLUME CRYSTALLIZATION OF METALLIC GLASS (Ni50Zr50)99.9P0.1 AS INVESTIGATED BY EXOELECTRON EMISSION (EEE) AND DIFFERENTIAL THERMAL ANALYS…
2002
Surface and volume crystallization of amorphous, melt-quenched (Ni50Zr50)99.9P0.1 alloy has been investigated by measurements of the temperature dependencies of the intensity of photostimulated exoelectron emission (EEE) and by differential scanning calorimetry (DSC). A comparison of these dependencies enables one to assess the tendency of the investigated materials to premature surface crystallization. For the (Ni50Zr50)99.9P0.1 alloy the surface crystallization occurs at temperatures distinctly lower than that for the crystallization in bulk. The activation energy for the surface crystallization, determined by the Ozawa method, i.e. from the shift of EEE peak corresponding to the surface…
Room-Temperature Cubic Phase Crystallization and High Stability of Vacuum-Deposited Methylammonium Lead Triiodide Thin Films for High-Efficiency Sola…
2019
Methylammonium lead triiodide (MAPI) has emerged as a high-performance photovoltaic material. Common understanding is that at room temperature it adopts a tetragonal phase and it only converts to the perfect cubic phase around 50-60 ºC. Most MAPI films are prepared using a solution-based coating process, yet they can also be obtained by vapor phase deposition methods. Vapor phase processed MAPI films have significantly different characteristics compared to their solvent processed analogous, such as a relatively small crystal grain sizes and short excited state lifetimes. Yet solar cells based on vapor phase processed MAPI films exhibit high power conversion efficiencies. Surprisingly, after…
Mechanism of crystallization of Co-cordierites from stoichiometric powdered glasses
2002
Abstract The influence of cobalt, as a divalent cation, on the crystallization behaviour of the cordierite based glasses was studied. Powdered glass specimens of stoichiometric composition 2MO 2Al 2 O 3 5SiO 2 (M=Co and/or Mg) were obtained and thermally treated at several temperatures and times, and the sequence of crystallization and their microstructural evolution were analysed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Results on the crystallization sequence showed that the steps in the crystallization path are independent of the nature of the divalent cation. The first crystalline phase detected displayed the μ-cordierite structure, i.e. a solid…
Influence of Co content on structural and magnetic properties of CoxFe84−xNb7B9 alloys
2003
Nanocrystallization of CoxFe84� xNb7B9 (x ¼ 17; 25, 33) alloys has been studied. Crystallization of specimens starts above 4501C. After annealing of specimens in the range 500–7001C, apart from amorphous component and BCC Fe-Co alloy, a non-magnetic component also appears, which is attributed to (Fe1� xCox)2Nb phase with a relative area of about 14%. Decrease of quadrupole splitting with annealing temperature indicates some possible ordering of the nonmagnetic phase. r 2002 Elsevier Science B.V. All rights reserved.