Search results for "Electron microscope"
showing 10 items of 784 documents
Ordering of fluorite-type phases in erbium-doped oxyfluoride glass ceramics
2018
In this study, novel transparent Er3+ doped glass ceramics were prepared from melt-quenched oxyfluoride glasses with general composition of Na2O-NaF-BaF2-YbF3-Al2O3-SiO2. The crystallization of fluorite (BaF2, BaF2-YbF3, NaF-BaF2-YbF3 and Na0.5-xYb0.5+xF2+2x) and distorted fluorite (rhombohedral Ba4Yb3F17 and tetragonal NaF-BaF2-YbF3) phases was analysed in glass ceramics with different BaF2 and YbF3 ratio. The phase composition and microstructure were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Intense red upconversion luminescence (UCL) was detected under near-infrared excitation resulting from three photon upconversion followed by cross-relaxation betw…
Effect of cobalt doping on the mechanical properties of ZnO nanowires
2016
Abstract In this work, we investigate the influence of doping on the mechanical properties of ZnO nanowires (NWs) by comparing the mechanical properties of pure and Co-doped ZnO NWs grown in similar conditions and having the same crystallographic orientation [0001]. The mechanical characterization included three-point bending tests made with atomic force microscopy and cantilever beam bending tests performed inside scanning electron microscopy. It was found that the Young's modulus of ZnO NWs containing 5% of Co was approximately a third lower than that of the pure ZnO NWs. Bending strength values were comparable for both materials and in both cases were close to theoretical strength indica…
Mechanical properties of sol–gel derived SiO2 nanotubes
2014
The mechanical properties of thick-walled SiO2 nanotubes (NTs) prepared by a sol–gel method while using Ag nanowires (NWs) as templates were measured by using different methods. In situ scanning electron microscopy (SEM) cantilever beam bending tests were carried out by using a nanomanipulator equipped with a force sensor in order to investigate plasticity and flexural response of NTs. Nanoindentation and three point bending tests of NTs were performed by atomic force microscopy (AFM) under ambient conditions. Half-suspended and three-point bending tests were processed in the framework of linear elasticity theory. Finite element method simulations were used to extract Young’s modulus values…
Naphthalimide imidazolium-based supramolecular hydrogels as bioimaging and theranostic soft materials
2020
1,8-Naphthalimide-based imidazolium salts differing for the alkyl chain length and the nature of the anion were synthesized and characterized to obtain fluorescent probes for bioimaging applications. First, their self-assembly behavior and gelling ability were investigated in water and water/dimethyl sulfoxide binary mixtures. Only salts having longer alkyl chains were able to give supramolecular hydrogels, whose properties were investigated by using a combined approach of fluorescence, resonance light scattering, and rheology measurements. Morphological information was obtained by scanning electron microscopy. In addition, conductive properties of organic salts in solution and gel state we…
The preparation and thermal evolution of polymeric gels with garnet stoichiometry in the CaOAl2O3SiO2 and CaOCr2O3SiO2 systems
1990
Abstract The synthesis of gels with garnet stoichiometry in the CaOAl 2 O 3 SiO 2 and CaOCr 2 O 3 SiO 2 systems and their evolution in thermal processing have been studied. Dried gels with the stoichiometry 3CaO.Al 2 O 3 .3SiO 2 show a homogeneous aspect without detectable crystalline phase. The thermal evolution of these gels indicates no formation of grossularite at temperatures up to 1000°C after 12 h. In the uvarovite garnet samples, 3CaO.Cr 2 O 3 .3SiO 2 , a small amount of crystalline phase was detected in the dried gels. The homogeneity of the gels was checked by scanning electron microscropy. The infrared study of these polymeric gels confirmed the presence of SiOMe (MeCr 3+ …
Microwave-induced electromigration in multicomponent metallic alloys
2010
The crystallization of amorphous FeCoCuZrAlSiB alloy ribbons during microwave heating was investigated in situ using time-resolved X-ray powder diffraction. The formation of the nanocrystalline α-(Fe,Co)(SiAl) phase during the primary crystallization stage is followed by the crystallization of the residual glassy matrix. Scanning electron microscopy analysis after microwave exposure reveals the formation of nanosized hillocks evenly distributed over the ribbon surfaces. Local chemical composition analysis by energy-dispersive spectroscopy shows that the surface clusters are enriched in Cu and Al. The occurrence of this typical electromigration effect imposes a strong restriction on the dura…
Electron microscopic investigations on amorphous polycarbonate
1967
Collapsible intact soil stabilisation using non-aqueous polymeric vehicle
2020
Abstract This paper presents the results of an experimental study that had the goal of understanding the effects of treatment with polyethylene glycol (PEG)/nanolime mixtures on collapsible soil behaviour. In a previous study, the use of pure PEG offered a good improvement in the stability of collapsible soil, but the stabilisation effect only lasted for a limited time. To investigate the stabilisation potential of PEG/nanolime systems for collapsible sand, different mixtures were prepared at increasing nanolime weight ratios. The suitability of the stabilised soil was examined on the basis of collapsibility, oedometer, shear, and water vapour permeability tests, and through optical microsc…
ANNEALING EFFECT ON COERCIVITY AND MICROHARDNESS IN SINTERED (Nd, Tb)15(Fe, Co, Al)78B7 MAGNETS
1999
The variation of the coercivity and microhardness with annealing (475–1150°C/3.6 ks) of sintered (Nd, Tb) 15 (Fe, Co, Al) 78 B 7 permanent magnet have been investigated. The data indicate that the coercivity reaches the mininum and the maximum at 600°C and 775°C, respectively. Optical and scanning electron microscopy and magnetic domain structure observations give no hints to any change in microstructure. Fitting of the Mössbauer spectra of permanent magnets for different coercivity ( i H c ) values revealed that magnetic hyperfine fields (B Hf ) on all Fe sites are reduced with the increase in i H c value and the higher value of the i H c corresponds to the higher value of the Mössbauer l…
Neutron scattering study of structural and magnetic size effects in NiO
2013
Nickel oxide powders with the grain size of 13–1500 nm have been studied by neutron scattering, scanning electron microscopy and vibrating sample magnetometry. We have found that the atomic structure and the antiferromagnetic ordering are nearly independent of the average size of grains. The existence of the uncompensated spins in nanoparticles with the grain size below 100 nm has been detected.