Search results for "Chemical engineering"
showing 10 items of 5892 documents
LiCrO2 Under Pressure: In-Situ Structural and Vibrational Studies
2018
The high-pressure behaviour of LiCrO2, a compound isostructural to the battery compound LiCoO2, has been investigated by synchrotron-based angle-dispersive X-ray powder diffraction, Raman spectroscopy, and resistance measurements up to 41, 30, and 10 Gpa, respectively. The stability of the layered structured compound on a triangular lattice with R-3m space group is confirmed in all three measurements up to the highest pressure reached. The dependence of lattice parameters and unit-cell volume with pressure has been determined from the structural refinements of X-ray diffraction patterns that are used to extract the axial compressibilities and bulk modulus by means of Birch&ndash
CuInS2 Films for Photovoltaic Applications Deposited by a Low-Cost Method.
2006
We report an atmospheric-pressure deposition method for preparing well-adhered and compact CuInS 2 films. The precursor film is obtained by a solution-coating technique and is subjected to a low-cost and safe one-step reduction-sulfurization treatment. A maximum thickness of 300 nm is achieved per layer, and up to three layers were sulfurized at a time. The obtained films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and visible-near-infrared (vis-NIR) spectrophotometry.
Structural investigation of four-centre photopolymerisation of bis-phthalamic bis-chalcone derivative in the crystalline state
1997
By combining the results obtained from an electron diffraction tilting series with solid state NMR and powder X-ray diffraction, it was possible to determine the unit cell parameters and space group of BPABC crystals grown from DMAA solution both before and after irradiation. Subsequently semi-empirical quantum mechanical and packing energy calculations led to a model structure which agreed well with all the electron diffraction data and thus provided insight into the cross-linking mechanism. © 1997 John Wiley & Sons Ltd.
An experimental methodology to study polymer crystallization under processing conditions. The influence of high cooling rates
2002
Abstract A new experimental route for investigating polymer crystallization under very high cooling rates (up to 2000°C/s) is described. A complete and exhaustive description of the apparatus employed for preparing thin quenched samples (100– 200 μm thick) is reported, the cooling mechanism and the temperature distribution across sample thickness is also analysed, showing that the final structure is determined only by the thermal history imposed by the fast quench apparatus. Details concerning the characterization techniques used to probe the final structure are reported, including density measurements and wide angle X-ray diffraction patterns. Experimental results concerning isotactic poly…
Elemental distribution and structural characterization of GaN/InGaN core-shell single nanowires by Hard X-ray synchrotron nanoprobes
2019
Improvements in the spatial resolution of synchrotron-based X-ray probes have reached the nano-scale and they, nowadays, constitute a powerful platform for the study of semiconductor nanostructures and nanodevices that provides high sensitivity without destroying the material. Three complementary hard X-ray synchrotron techniques at the nanoscale have been applied to the study of individual nanowires (NWs) containing non-polar GaN/InGaN multi-quantum-wells. The trace elemental sensitivity of X-ray fluorescence allows one to determine the In concentration of the quantum wells and their inhomogeneities along the NW. It is also possible to rule out any contamination from the gold nanoparticle …
The continuous cooling transformation (CCT) as a flexible tool to investigate polymer crystallization under processing conditions
2009
An experimental route for investigating polymer crystallization over a wide range of cooling rates (from 0.01 to 1000◦C/s) and pressures (from 0.1 to 40 MPa) is illustrated, using a method that recalls the approach adopted in metallurgy for studying structure development in metals. Two types of experimental setup were used, namely an apparatus for fast cooling of thin films (100–200 μm thick) at various cooling rates under atmospheric pressure and a device (based on a on-purpose modified injection molding machine) for quenching massive samples (about 1–2 cm3) under hydrostatic pressure fields. In both cases, ex situ characterization experiments were carried out to probe the resulting struct…
Synthesis of single crystalline sub-micron rutile TiO2 rods using hydrothermal treatment in acidic media
2014
Size engineered rutile sub-micron rods were obtained from nanostructured titania under acidic conditions. The synthesis was performed by hydrothermal treatment starting from TiO2-P25 and HCl. The synthesis proceeds in less than two hours and can be up-scaled to several grams in a one-pot reaction by increasing the reaction time. The product is single-phase, and the particles are single crystalline as confirmed by electron diffraction and powder X-ray diffraction analysis. The length of the particles can be varied over a wide range from 100 nm to 1.3 μm by changing the acid concentration. Particle growth is proposed to proceed by a dissolution-recrystallization process via soluble [TiCl6]2− …
STRUCTURE AND MAGNETIC PROPERTIES OF COBALT FERRITE PARTICLES PRODUCED BY METHOD OF PYROLYTIC SYNTHESIS
2008
ABSTRACT Magnetic fine particles of cobalt ferrite have been prepared by method of pyrolytic synthesis. X-ray diffraction confirmed the formation of single-phase cobalt ferrite nanoparticles in the range 6–50 nm. The size of the particles varies depending on matrix dispersity and mass content in the organic precursors. A large coercivity observed to be small for smaller single-domain particles due to superparamagnetic behavior.
Analysis of Dissolved-Gas Atomization: Supercritical CO2 Dissolved in Water
2010
Supercritical dissolved-gas atomization is an atomization process in which carbon dioxide at temperature and pressure above its critical point is used as the atomizing gas. The spray characteristics in terms of droplets size and distribution have been experimentally studied using a laser diffraction method based on a Malvern apparatus. The main parameter that influences the droplets size is the gas-to-liquid mass ratio (GLR); the injection pressure in the range of 7.4-13 MPa has a minor effect. Upon variation of the GLR from 0.5 to 3, the droplet mean diameter changes from about 8.0 to 2.0 μm; very narrow droplet size distributions are also produced. From the point of view of the atomizatio…
A multi-step mechanism and integrity of titanate nanoribbons.
2014
A one-step hydrothermal treatment of TiO2 powders under strongly basic conditions has been used to synthesize titanate nanoribbons. The nanoparticles were thoroughly characterized using several methods including transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectrometry (XPS) to determine their morphological, structural and chemical characteristics. The influence of the nature and size of the TiO2 precursor and of the reaction duration on the formation of the nanoribbons was investigated. The conditions required to obtain only titanate nanoribbons with a width ranging from 100 to 200 nm and several tens of micrometers in length w…