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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Morozov E. V., Martyanov O. N.
Заглавие : Probing flocculant-induced asphaltene precipitation via NMR imaging: from model toluene-asphaltene systems to natural crude oils
Коллективы : Russian Science Foundation [15-19-00119]
Место публикации : Appl. Magn. Reson.: Springer, 2016. - Vol. 47, Is. 2. - P.223-235. - ISSN 0937-9347, DOI 10.1007/s00723-015-0741-9. - ISSN 1613-7507(eISSN)
Примечания : Cited References:46. - This research was performed with the financial support of Russian Science Foundation (project no. 15-19-00119).
Предметные рубрики: PETROLEUM ASPHALTENES
MOLECULAR-DYNAMICS
AGGREGATION
MICROSCOPY
SCATTERING
RESONANCE
SEDIMENTATION
ASSOCIATION
CALORIMETRY
RELAXATION
Аннотация: An nuclear magnetic resonance (NMR) imaging approach for studying flocculant-induced asphaltene precipitation processes is introduced in this report. Unlike commonly accepted techniques, which primarily measure aggregation processes on the submicron scale (the level of asphaltene molecules and their aggregates), NMR imaging demonstrates the capability to obtain new useful information about bulk system behavior on the macro scale. To reveal the capabilities of the method, the model toluene-asphaltene system and two samples of natural crude oils with different chemical composition and physical properties (such as asphaltene content and density) were employed for experiments. The process of colloidal suspension formation and two different patterns of its evolution were observed depending on both the asphaltene content and the flocculant concentration. In the first pattern, the flocculant-induced precipitation leads to the slow uniform compacting of the suspension and descent of the sedimentation front, whereas the second pattern is characterized by sediment accumulation and the upwards drift of the front. It was found that the behavior of the precipitated asphaltenes in the model system correlates well with those observed in natural crude oils. The results achieved in this work are in agreement with the data obtained previously via other techniques. Thus, NMR imaging proved to be an efficient method for probing flocculant-induced precipitation in crude oils.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zharkov S. M., Kveglis L. I.
Заглавие : Electron-beam-initiated crystallization of iron-carbon films
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2004. - Vol. 46, Is. 5. - P969-974. - ISSN 1063-7834, DOI 10.1134/1.1744977
Примечания : Cited References: 34
Предметные рубрики: AMORPHOUS-GERMANIUM FILMS
EXPLOSIVE CRYSTALLIZATION
PATTERN-FORMATION
TEMPERATURE
MICROSCOPY
MECHANISM
Аннотация: A structure formed in nanocrystalline iron-carbon films exposed to an electron beam was studied. Explosive crystallization (EC) with the formation of dendrite and cellular-dendritic instabilities at a rate of up to 1 cm/s was observed. It was shown that the dependence between the growth rate of dendrite branches (or cells) during EC and the rounding radius of dendrite branch tips can be approximately described by equations used to calculate the crystal growth in supercooled melts. To explain the EC mechanism, a model of a liquid zone formed at the crystallization front was used. It was shown that the liquid zone arises due to energy accumulated in the film in the nanocrystalline state. It was assumed that this energy was accumulated due to the energy of elastic stresses. (C) 2004 MAIK "Nauka / Interperiodica".
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Peng J. L., Bulcock S., Belobrov P. I., Bursill L. A.
Заглавие : Surface bonding states of nano-crystalline diamond balls
Место публикации : Int. J. Mod. Phys. B: WORLD SCIENTIFIC PUBL CO PTE LTD, 2001. - Vol. 15, Is. 31. - P4071-4085. - ISSN 0217-9792, DOI 10.1142/S0217979201007865
Примечания : Cited References: 20
Предметные рубрики: PLASMON RESPONSE
POWDER
SPECTROSCOPY
MICROSCOPY
SILICON
SI(111)
Ключевые слова (''Своб.индексиров.''): diamond--article--crystal structure--electron--energy transfer--nanoparticle--particulate matter--structure analysis--surface property--transmission electron microscopy
Аннотация: The rough surface of nano-crystalline diamond spheres induces surface electronic states which appear as a broadened pre-peak over approx. 15 eV at the C K-edge energy threshold for carbon in the parallel electron energy loss spectrum (PEELS). This appears to be at least partially due to 1s-pi* transitions, although typically the latter occupy a range of only 4 eV for the sp(2) edge of highly-oriented pyrollytic graphite (HOPG). No pi* electrons appear in the conduction band inside the diamond particles, where all electrons are sp(3) hybridized. PEELS data were also obtained from a chemical vapour deposited diamond film (CVDF) and gem-quality diamond for comparison with the spectra of nano-diamonds. The density of sp(2) and sp(3) states on the surface of diamond nano-crystals is calculated for simple structural models of the diamond balls, including some conjecture about surface structures. The results are used to interpret the sp(2)/sp(3) ratios measured from the PEELS spectra recorded as scans across the particles. Surface roughness at the atomic scale was also examined using high-resolution transmission electron microscopy (HRTEM) and electron nano-diffraction patterns were used to confirm the crystal structures.
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