Search results for "Crystallization"

Mechanical Characterization of Polymers on a Nanometer Scale through Nanoindentation. A Study on Pile-up and Viscoelasticity

2007

The analysis of nanoindentation force curves collected on polymers through the common Oliver and Pharr procedure does not lead to a correct evaluation of Young’s modulus. In particular, the estimated elastic modulus is several times larger than the correct one, thus compromising the possibility of a nanomechanical characterization of polymers. Pile-up or viscoelasticity is usually blamed for this failure, and a deep analysis of their influences is attempted in this work. Piling-up can be minimized by indenting on a true nanometer scale, i.e., at penetration depth smaller than 200 nm. On the other side, it is common knowledge that fast indentations minimize the effect of viscoelasticity. How…

Gold Nanoparticle Growth Monitored in situ Using a Novel Fast Optical Single-Particle Spectroscopy Method

2007

Size- and shape-dependent optical properties of gold nanorods allow monitoring their growth using a novel fast single-particle spectroscopy (fastSPS) method. FastSPS uses a spatially addressable electronic shutter based on a liquid crystal device to investigate particles randomly deposited on a substrate, orders of magnitude faster than other techniques. We use fastSPS to observe nanoparticle growth in situ on a single-particle level and extract quantitative data on nanoparticle growth.

New Insights into the Crystallization Process of Calcium Carbonate by a Contact-Free in situ Scattering Technique using a Levitating Drop Method

2008

Molecules Forced to Interact: Benzene and Pentafluoroiodobenzene

2020

The in situ low-temperature (co)crystallization of liquids and gases, followed by a detailed structural study, represents an approach to engineer and discover novel materials that are not formed under ambient conditions. Single-crystal X-ray diffraction revealed dimorphism along with a hierarchy of particular interactions in pentafluoroiodobenzene, C6F5I(1), and its benzene cocrystal (C6F5I)(2)center dot C6H6 (2). There are four polymorphs, two of 1, 1-I and 1-II, and two of 2, 2-I and 2-II, and they all are principally dominated by I center dot center dot center dot F and F center dot center dot center dot F halogen interactions. The nature and the contribution of different interactions we…

Intramitochondrial crystalloids in rat pinealocytes.

1982

In the present study the rare occurrence of intramitochondrial crystalloid inclusions in the rat pinealocytes is described. They lie within the mitochondrial matrix and consist of a lattice of moderately electron-dense lines. Intersections at regular intervals form rhomboid-like subunits. The significance of these inclusions is not known.

Indentation test as a tool for monitoring the solidification process during injection molding

2003

An inline method for monitoring the solidi-fication process during the injection molding of semicrystalline polymers is demonstrated. The method has been applied to various poly(ethylene terephthalate) (PET) and poly(buthylene terephthalate) (PBT) samples. The technique is based on a simple device by which an additional ejector pin is pushed onto the injection-molded part with a fixed force at different times during the solidification phase while the mold remains closed. The residual deformation (the so-called indentation depth) due to the applied load is measured offline after ejection. By the performance of indentation at different times during the cooling phase, an indentation depth prof…

Simulación de un proceso industrial de cristalización de Cloruro de Sodio (NaCl) y aplicaciones

2014

RESUMEN: La cristalización a partir de disoluciones es importante industrialmente dada la gran variedad de sustancias que se comercializan cristalizadas. Para mejorar la enseñanza aprendizaje de esta Operación Básica, en este trabajo, realizado como Trabajo Fin de Carrera de Ingeniería Química, se ha implementado un programa de simulación de una cristalización, partiendo de los datos de una cristalización industrial de NaCl. El objetivo ha sido manejar herramientas de cálculo para simular y optimizar esta operación, lo que permite conocer más profundamente el proceso de la cristalización y la utilización de las herramientas de cálculo, es decir, utilizar simultáneamente los conocimientos ad…

Cation-translocation based isomerism offers a tool for the expansion of compressed helicates.

2021

A series of compressed M[Li313Ti2] (M = Li, Na, K, Rb, Cs) and expanded helicates M4[13Ti2] has been obtained. The helicates Li3[M13Ti2] or M4[13Ti2] with M = Na+, K+, Rb+, or Cs+ adopt the expanded structure in solution. By crystallization the compressed structures M[Li313Ti2] (M = Na, Rb) are obtained. This represents an example of cation-translocation based isomerism.

Spontaneous Resolution of a Triple‐Stranded Dinickel(II) Helicate Generated via Intermolecular Transamination Reaction of S ‐Methylisothiocarbohydraz…

2008

The reaction of S-methylisothiocarbohydrazide hydroiodide [H2NNHC(SCH3)NNH2·HI] with NiCl2·6H2O in water at room temperature yielded a triple-stranded dinickel(II) helicate [NiII(L1–L1)3NiII]I4·4H2O (14+·4I–·4H2O), where L1–L1 = H2NNHC(SCH3)NNC(SCH3)NHNH2, in 35 % yield, which spontaneously separates in enantiomers upon crystallization. The enantiomers do not racemize at room temperature, even not after 15 h of heating at 90 °C. X-ray diffraction structures of both enantiomers, chiroptical and magnetic properties of 14+·4I–·4H2O are reported. Demetallation of the complex by treatment with S2– resulted in 3,6-bis(methylthio)-1,4-dihydro-1,2,4,5-tetrazine (2). Compound 2 undergoes 2-e– oxidat…

Mixed Titanium–Hafnium Chloridometallate Complexes

2007

The addition of either NEt 3 BzCl or [Ph 3 PNPPh 3 ]Cl (1 equiv. chloride per metal) to a 1:1 mixture of HfCl 4 and TiCl 3 in SOCl 2 results in Ti oxidation and leads to the corresponding salts of the [TiHfCl 10 ] 2- ion. A solution IR investigation in the v(M-Cl) region indicates that this ion is in equilibrium with the homodimetallic [Ti 2 Cl 10 ] 2- and [Hf 2 Cl 10 ] 2- ions. An X-ray study of the NEt 3 Bz + salt reveals an edge-sharing bioctahedral dianion sitting on a crystallographic inversion centre. The crystal is a solid solution of different species with compositional disorder at the metal site, each metal position having the occupancy Ti 0.685 Hf 0.315 . The M-M and M-Cl distance…