Search results for "Diffraction"
showing 10 items of 1584 documents
<title>Bragg and asymmetric-relief reflection gratings in As-S-Se thin films</title>
2005
Bragg and asymmetric-relief gratings and their formation in the amorphous As-S-Se films are discussed. Due to the high refractive index and its photoinduced change, the films are useful in holography. The thickness of the As0.4S0.15Se0.45 and As0.4S0.3Se0.3 films used in the Bragg gratings is optimized. The dependence of the dimaction efficiency of the asymmetric-relief gratings on the conditions of recording, chemical treating, and reading out (polarization and angle) is studied.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Displacement measurement through DIC and DSPI techniques in cold-expanded holes
2008
In this paper, the displacement field induced by the split-sleeve cold expansion of holes was measured using both digital image correlation (DIC) and digital speckle pattern interferometry (DSPI) techniques. Thus, the experimental results, which were evaluated on the inlet surface of a 6082-T6 aluminium plate, were compared with those from theoretical prediction. DIC provided accurate measurements up to the elastic-plastic boundary, whereas the DSPI technique highlighted the changes of displacement in the elastic domain. Prediction of the displacement based on the existing analytical model agreed with the experimental results achieved with both techniques. Possible explanations for the diff…
Highly stable and porous porphyrin-based zirconium and hafnium phosphonates – electron crystallography as an important tool for structure elucidation
2018
The Ni-metallated porphyrin-based tetraphosphonic acid (Ni-tetra(4-phosphonophenyl)porphyrin, Ni-H8TPPP) was used for the synthesis of highly porous metal phosphonates containing the tetravalent cations Zr4+ and Hf4+. The compounds were thoroughly characterized regarding their sorption properties towards N2 and H2O as well as thermal and chemical stability. During the synthesis optimization the reaction time could be substantially decreased under stirring from 24 to 3 h in glass vials. M-CAU-30, [M2(Ni-H2TPPP)(OH/F)2]·H2O (M = Zr, Hf) shows exceptionally high specific surface areas for metal phosphonates of aBET = 1070 and 1030 m2 g-1 for Zr- and Hf-CAU-30, respectively, which are very clos…
Characterisation of films and nanopaper obtained from cellulose synthesised by acetic acid bacteria
2016
Bacterial cellulose (BC) samples were obtained using two culture media (glucose and glucose+fructose) and two bacteria (Komagataeibacter rhaeticus and Komagataeibacter hansenii). Nanopaper was obtained from the BC through oxidation and both were studied to determine the impact of culture media and bacteria strain on nanofiber structure and mechanical properties. AFM and SEM were used to investigate fibre dimensions and network morphology; FTIR and XRD to determine cellulose purity and crystallinity; carboxyl content, degree of polymerisation and zeta potential were used to characterise nanofibers. Tensile testing showed that nanopaper has up to 24 times higher Young's modulus (7.39GPa) than…
Polarized neutron diffraction and Mössbauer spectral study of short-range magnetic correlations in the ferrimagnetic layered compounds(PPh4)[FeIIFeII…
2002
Short-range antiferromagnetic correlations have been studied in the layered compounds (PPh 4 ) [Fe I I Fe I I I (ox) 3 ] and (NBu 4 ) [Fe I I Fe I I I (ox) 3 ] by neutron polarization analysis and Mossbauer spectroscopy. Polarized neutron diffraction profiles obtained between 2 and 50 K on (d 2 0 -PPh 4 ) [Fe I I Fe I I I (ox) 3 ] show no magnetic Bragg scattering; the lack of such scattering indicates the absence of long-range magnetic order. However, a broad asymmetric feature observed at a Q of ca. 0.8 A - 1 is attributed to two-dimensional short-range magnetic correlations, which are described by a Warren function. The correlation length is ca. 50 A between 2 and 30 K and then decreases…
Influence of B-site chemical ordering on the dielectric response of the Pb(Sc1/2Nb1/2)O3relaxor
2001
The influence of chemical B-site ordering between Sc3+ and Nb5+ cations on the properties of the Pb(Sc1/2Nb1/2)O3 (PSN) relaxor has been investigated. Depending of the degree of ordering, PSN exhibits different behaviours. For a completely disordered material, a relaxor–ferroelectric phase transition is observed at 379 K by DSC. Ordering between Sc3+ and Nb5+ cations on the B-site of the perovskite structure leads to a non-homogeneous material constituted of two phases: ordered and disordered phases. The phase transition temperature of the ordered phase is confirmed to be lower (346 K) than that of the disordered phase. It appears that the phase transition of the disordered phase is shifted…
The Structural and Dielectric Properties of the Li0.005Na0.995NbO3Ceramics
2009
The sodium niobate-lithium niobate (Li x Na1 − x NbO3) compounds were synthesized using conventional solid-state processing. Phase analysis was performed by X-Ray diffraction, and microstructural morphology was assessed by scanning electron microscopy. The dielectric measurements were performed in heating and cooling processes without and under axial pressure up to 120 MPa. It has been stated, that the maximum of electric permittivity ϵ (T) becomes more diffused with the increase of axial pressure and the temperature of phase transition T0 decreases. The value of tanδ increases with the increase of axial pressure and its local maximum shifts towards lower temperatures.
Structure and Lattice Dynamics in PLZT 8/65/35 Ceramics Irradiated by High-Current Pulsed Electron Beam
2004
The comprehensive study of high-current pulsed electron irradiation effect on the structure and lattice dynamics as well as optical properties of PLZT 8/65/35 ceramics have been performed. X-ray powder diffraction studies shown the transformation of the rhombohedral perovskite structure R3m (Z = 1) into orthorhombic Pmmm (Z = 1) for the sample irradiated by one pulse (dose 4 × 1014 electrons/cm2) and, as a consequence, the changes in number of phonon modes position, oscillators strength and damping in IR and Raman spectroscopy data. However neutron powder diffraction measurements of multiple irradiated samples have not been revealed any structural distortions. Dielectric parameters have sho…
Oxide or carbide nanoparticles synthesized by laser ablation of a bulk Hf target in liquids and their structural, optical, and dielectric properties
2016
International audience; Laser ablation of a bulk Hf target in deionized (DI) water, ethanol, or toluene was carried out for the production of nanoparticles' colloidal solutions. Due to the interaction of the ablation plasma plume species with the species which are produced by the liquid decomposition at the plume-liquid interface, hafnia (HfO2) nanoparticles are synthesized in DI water, hafnium carbide (HfC) nanoparticles in toluene, and a mixture of these in ethanol. The hafnia nanoparticles are in the monoclinic low temperature phase and in the tetragonal and fcc high temperature phases. Their size distribution follows log-normal function with a median diameter in the range of 4.3–5.3 nm.…
Determination of trace amounts of β tegafur in commercial α tegafur by powder X-ray diffractometric analysis.
2011
Abstract Objectives The main objective of this work was to develop a suitable analytical technique for determining trace amounts of the thermodynamically stable solid form in bulk samples of metastable form, to a sensitivity of 0.005%–1.0%. Tegafur (5-fluoro-1-(tetrahydro-2-furyl)-uracil) α and β crystalline forms were used as a model for this problem. Methods The trace content of the thermodynamically stable β polymorphic form in tegafur samples was increased by promoting phase transition from the bulk of thermodynamically metastable α form to β form, and achieving sufficient β form content for a quantitative powder X-ray diffractometry (PXRD) analysis. The phase transition was stimulated …