Search results for "Crystallization"
showing 10 items of 774 documents
Hierarchical Assembly of TiO2 Nanoparticles on WS2 Nanotubes Achieved Through Multifunctional Polymeric Ligands
2007
Thefunctionalization of nanotubes is required in order to bene-fit from their outstanding properties, as any application inmaterials and devices is hindered by processing and manipu-lation difficulties. Only the attachment of appropriate chem-ical functionalities on the nanotube surface allows tailoringof the properties for the respective applications. As an ex-ample, the enhancement of the nanotube solubility is onemajor task since most pristine nanotubes are insoluble inboth water and organic solvents. Thus, the improvement ofthe solubility by chemical functionalization is an importantconcept for synthetic chemists and materials scientists. Tai-loring of the surface chemical bonds might a…
In situ nucleation of carbon nanotubes by the injection of carbon atoms into metal particles.
2007
The synthesis of carbon nanotubes (CNTs) of desired chiralities and diameters is one of the most important challenges in nanotube science and achieving such selectivity may require a detailed understanding of their growth mechanism. We report the formation of CNTs in an entirely condensed phase process that allows us, for the first time, to monitor the nucleation of a nanotube on the spherical surface of a metal particle. When multiwalled CNTs containing metal particle cores are irradiated with an electron beam, carbon from graphitic shells surrounding the metal particles is ingested into the body of the particle and subsequently emerges as single-walled nanotubes (SWNTs) or multiwalled nan…
Preparation and recrystallization behavior of spray-dried co-amorphous naproxen–indomethacin
2016
To improve the dissolution properties and the physical stability of amorphous active pharmaceutical ingredients, small molecule stabilizing agents may be added to prepare co-amorphous systems. The objective of the study was to investigate if spray-drying allows the preparation of co-amorphous drug-drug systems such as naproxen-indomethacin and to examine the influence of the process conditions on the resulting initial sample crystallinity and the recrystallization behavior of the drug(s). For this purpose, the process parameters inlet temperature and pump feed rate were varied according to a 2(2) factorial design and the obtained samples were analyzed with X-ray powder diffractometry and Fo…
Reaction Sequence in the Preparation of NiAl2O4 Spinel-Mullite Composites by Sol-Gel
2005
NiAl 2 O 4 spinel-mullite composites were prepared by simultaneous replacement of Al by Ti and/or Ni in 3:2 stoichiometric mullite. Specimens having nominal compositions 3(Al 2-2x Ni x Ti x O 3 ).2SiO 2 (x = 0, 0.025, 0.05, 0.2) and 3(Al 2-x M x O 3) .2SiO 2 (M = Ni 2+ or Ti 4+ and x = 0.05) were synthesized by sol-gel techniques, which provide homogeneous gels in the SiO 2 -Al 2 O 3 system. Gel structures investigated by infrared (IR) spectroscopy revealed the formation of Al-O-Si bonds in dried gels. The reaction sequence of gel-derived glasses, previously obtained by preheating gels at 750°C for 3 h, was evaluated by X-ray powder diffraction (XRD) and ultraviolet-visible (UV-vis) spectro…
Nucleation kinetics in deionized charged colloidal suspension
2011
A systematic experimental study on the nucleation, crystallization and crystal-growth of one-componentcharged colloidal particles (122 nm diluted in pure water with densities between 0.5 μm−3bnpb5 ...
Experimental visualization of inoculation using a charged colloidal model system
2012
Inoculation is widely used to tune the microstructure of a polycrystalline solid from the melt and thus its material properties. We present here a systematic time resolved experimental study of inoculation in a charged colloidal model system investigating the changes of the crystallization scenario upon adding spherical seeds and show that the nucleation kinetics solely determines the resulting microstructure.
Crystal growth kinetics in binary mixtures of model charged sphere colloids
2007
From the formation of crystalline materials from their melts is at the heat of many important industrial processes. A rigorous and comprehensive understanding of the crystallization process, however, is still lacking, and its experimental and theoretical investigation has remained a considerable challenge. We studied the crystal growth velocities v of random composition body centred cubic (rc-bcc) colloidal crystals formed from a shear molten binary mixture of charged colloidal spheres suspended in deionized water. We used Bragg microscopy at constant particle number density n and as a function of the number fraction of large particles p. With increasing p the growth velocity v first drops …
Complexes of Co(II) and Zn(II) with ofloxacin. Crystal structure of [Co(oflo)2(MeOH)2].4MeOH.
2002
Abstract Ofloxacin (oflo) is able to interact with Co(II) and Zn(II) salts to form complexes with the general formula [M(oflo) 2 ] · 4H 2 O, (M = Co, Zn). Bonding takes place through one of the oxygen atoms of the carboxylate group (acting as a monodentate) and the oxygen atom of the ketonic group. The IR bands of the carboxylic and ketonic group at 1713 and 1622 cm −1 , respectively, shift to 1615 and 1575 cm −1 in the complexes. After dissolution in methanol, complex [Co(oflo) 2 ] · 4H 2 O crystallizes as [Co(oflo) 2 (MeOH) 2 ] · 4MeOH, where Co(II) ion is in an octahedral environment of oxygen atoms. This compound crystallizes in the triclinic system, spatial group P‐1, with unit cell di…
Complexes of Ni(II) and Cu(II) with ofloxacin. Crystal structure of a new Cu(II) ofloxacin complex.
2001
Several coordination compounds formed between Ni(II) or Cu(II) with ofloxacin have been synthesised and characterised. According to elemental chemical analysis and FT-IR spectroscopy data, direct reaction of Ni(II) and Cu(II) salts with ofloxacin leads to formation of precipitates for which mass spectrometry demonstrates their polymeric nature. However, crystalline [Cu(oflo)2(H2O)].2H2O is formed if the reaction is carried out in the presence of ammonia. This complex crystallises in the triclinic system, space group P-1 with a=9.2887(12), b=11.2376(14), c=17.874(2) A, alpha=92.12(3), beta=95.39(3), gamma=91.71(3) degrees and Z=2. The local geometry around the Cu(II) ion is a slightly distor…
Dehydration of melt inclusions in olivine and implications for the origin of silica-undersaturated island-arc melts
2019
Highlights • New experiments with melt inclusions in olivine at 1200 °C and 300 MPa. • Coupled behavior H2O and SiO2 in inclusions during re-hydration and dehydration. • SiO2 mobility results from formation/destruction of metal vacant olivine. • SiO2-undersaturated arc melt inclusions may originate by dehydration. • New method to assess initial H2O in dehydrated inclusions. Abstract Primary subduction-related magmas build up modern continental crust and counterbalance massive recycling of crustal material into the deep mantle occurring at this tectonic setting. Melt inclusions in Mg-rich olivine are believed to be the best probes of primary subduction-related melts. However, unexpectedly, m…