Search results for "RAMAN"
showing 10 items of 1328 documents
Quantifying the Covalent Functionalization of Black Phosphorus
2020
Abstract A straightforward quantification method to consistently determine the overall functionalization degree of covalently modified two‐dimensional (2D) black phosphorus (BP) by Raman spectroscopy has been carried out. Indeed, the successful reductive methylation of the BP lattice using sodium intercalation compounds and exhibiting different functionalization degrees has been demonstrated by 31P‐magic angle spinning (MAS) NMR spectroscopy. Furthermore, the correlation of 31P‐MAS NMR spectroscopy and statistical Raman spectroscopy (SRS) revealed the first method to determine the functionalization degree of BP solely by evaluating the intensities of distinct peaks in the Raman spectra of t…
Spectrometric analysis of inner divertor materials of JET carbon and ITER-like walls
2019
Abstract One of main reasons of the Joint European torus (JET) transformation from the carbon (JET-C) to ITER-like (JET-ILW) wall was high tritium retention of carbon. In order to compare the tritium retention, samples of analogous positions of the plasma-facing side of vertical tiles No. 3 of two campaigns: JET-C (2008–2009) and JET-ILW (2011–2012) were cut out. Temperature-programmed tritium desorption spectrometry in He + 0.1% H2 gas flow showed that JET-C sample without a tungsten coating had by a factor of >20 higher surface concentration of tritium than JET-ILW tungsten-coated sample: 4.9 × 1013 and 1.7–2.2 × 1012 T atoms/cm2 respectively. Installation of metallic plasma facing wall i…
Sulfonēta poliēterēterketona un grafēna kompozītmembrānas
2022
Darba ietvaros veica grafēna pārnešanu no vara folijas uz polietilēna pamatni un SPĒĒK membrānām ar karstās presēšanas metodi. Izpētīja temperatūras ietekmi uz pārnestā un virsū folijai palikušā grafēna kvalitāti, par tās kritēriju izmantojot grafēnam raksturīgo Ramana spektroskopijas signālu intensitāšu attiecību un ar grafēnu pārklāto membrānu pretestību izmaiņas.
Kamils Ramans : izstāde Kamila Ramana simtgades piemiņai
2017
2017. gada 30. aprīlī ievērojamais docents un pētnieks Kamils Ramans svinētu 100 gadu jubileju. LU Bibliotēkas Dabaszinātņu bibliotēka sadarbībā ar LU Ģeogrāfijas un Zemes zinātņu fakultāti piedāvā iepazīties ar izstādi Kamila Ramana simtgades piemiņai. Izstādē var iepazīties ar docenta dzīves gājumu, kā arī būtisko devumu ģeogrāfijas un ainavu zinātnē. Izstāde veidota trīs daļās: pirmajā daļā aplūkots Kamila Ramana dzīves gājums un nozīmīgākie sasniegumi, otrajā daļā apkopotas nozīmīgākās publikācijas, bet noslēgumā LU Ģeogrāfijas un zemes zinātņu fakultāte piedāvā kolēģu un laika biedru atmiņas par Kamila Ramana aktīvo darbību Latvijas Universitātē.
Micro-Raman characterization of graphene grown on SiC(000-1)
2014
Graphene (Gr) was grown on the C face of 4H-SiC under optimized conditions (high annealing temperatures ranging from 1850 to 1950°C in Ar ambient at 900 mbar) in order to achieve few layers of Gr coverage. Several microscopy techniques, including optical microscopy (OM), ?Raman spectroscopy, atomic force microscopy (AFM) and atomic resolution scanning transmission electron microscopy (STEM) have been used to extensively characterize the lateral uniformity of the as-grown layers at different temperatures. ?Raman analysis provided information on the variation of the number of layers, of the stacking-type, doping and strain.
Structural characterization of selective area growth GaN nanowires by non-destructive optical and electrical techniques
2015
The growth selectivity and structural quality of GaN nanowires obtained by plasma-assisted molecular beam epitaxy on pre-patterned GaN(0001) templates are investigated by means of non-destructive techniques. Optimum control over the nanowire arrangement and size requires a pitch between the mask apertures below twice the diffusion length of Ga atoms. Lower pitches, however, seem to slightly diminish the structural quality of the material, as revealed by the increase of the Raman peak linewidths. The photoluminescence spectra of the nanowires show a considerable presence of basal plane stacking faults, whose density increases for decreasing nanowire diameter. The capabilities of Kelvin probe…
A compact Raman microprobe/microscope: Analysis of polydiacetylene Langmuir and Langmuir-Blodgett films
1991
A compact Raman microprobe/microscope has been developed which contains no wavelength dispersive elements. Multilayer dielectric filters, tuned by rotation, provide sufficient wavelength selectivity for taking Raman spectra and forming Raman images of samples as small as 1 μm in diameter. The application of the instrument is demonstrated by Raman spectra and images of polydiacetylene Langmuir and Langmuir-Blodgett films.
Characterization of Flux-Grown SmxNd1–xVO4 Compounds and High-Pressure Behavior for x = 0.5
2019
The crystal structure and the vibrational and optical characteristics of flux-grown mixed lanthanide vanadate compounds SmxNd1–xVO4 (x = 0, 0.1, 0.25, 0.5, 0.75 and 1) are reported. A linear, monot...
FRACTAL STRUCTURES IN SINGLE CRYSTALS OF FERROELECTRIC LITHIUM NIOBATE GROWN UNDER STRONGLY UNSTABLE CONDITIONS
2009
Atomic force microscopy studies of lithium niobate single crystals containing heterogeneously distributed lanthanide (Gd) admixture and a regular domain structure of 100 nm to 1 μm steps obtained under conditions of severe thermal instability have revealed fractal structures of the size of 10 to 100 nm within regions of the regular domain structures. A super-structure of clustered defects with 1–2 nm steps explaining results of Raman spectra analysis is supposed to exist in the cation sub-lattice and formation of periodic fractal structures of the size of ∼1 nm–100 μm is suggested to take place in lithium niobate single crystals containing lanthanide admixture.
Measure of a limestone weathering degree using Laser Scanner.
2013
The weathering degree of the building materials and natural stones is generally quantified as the decrement of some mechanical features that can be measured experimentally by means of compressive tests or point load tests in the laboratory or Schmidt hammer tests carried out in situ. Such destructive or damaging tests are unacceptable in case of cultural heritage since even small amounts of damage must be avoided. This work shows a correlation between Schmidt hammer rebound values and the reflectivity that is detected by means of terrestrial scanner laser; therefore it allows assessing the weathering degree of buildings or stones in situ. The results demonstrate that such an investigation c…