1 Часть первая опубликована в [1], вторая-в [2], третья-в [3], четвертая-в [4]. Для повышения точности полученных результатов сравниваются два метода исследования процессов смачивания и растекания на твердой подложке. В первом методе используются капли жидкости, а во втором-пузырьки. При растекании формы капель и пузырьков изменяются, и это количественно может быть оценено только посредством уравнения Лапласа, но применяется уравнение только в случае пузырьков (второй метод). Это исключает в случае первого метода контроль за чистотой поверхности растекающейся капли. Влияние микрозагрязнений на результаты рассматривается на основе прецизионных расчетов, проведенных для обоих методов. Рассчитаны кривые растекания нанопузырьков с начальными диаметрами 20 и 10 нм на подложках с различной смачиваемостью, причем смачиваемость оценивается не по числовой величине краевого угла, а по соответствующим ему легко реализуемым примерам таких подложек Г, Ф и Н х , где х-доля поверхности под пузырьком, покрытая молекулами ионогенного собирателя: 0,8; 0,6; 0,4 и 0,2. Кривые растекания наглядно иллюстрируют диапазон возможного растекания нанопузырьков от предельного на подложке Г до практически нулевого на подложке Ф, а также источники энергетического обеспечения процесса растекания и причины их истощения. Информативность кривых растекания обусловлена тем, что при их расчете применяются более десяти параметров пузырька и подложки. При использовании реагентов активация процесса флотации может распространяться на пузырьки большего размера. Ключевые слова: нанопузырьки, уравнение Лапласа, поверхностное натяжение, краевой угол, смачиваемость твердой поверхности, сферичность капель и пузырьков, кривые растекания, подложка с предельной гидрофобностью, подложка с предельной гидрофильностью, подложка с неполной смачиваемостью. Мелик-Гайказян В.И.-докт. хим. наук, проф., рук-ль лаборатории поверхностных явлений и флотации ЮЗГУ (305040, г. Курск, ул. 50 лет Октября, 94).
Fast image reconstruction for fluorescence microscopy AIP Advances 2, 032174 (2012) Spectrally resolved fluorescence lifetime imaging microscope using tunable bandpass filters Rev. Sci. Instrum. 83, 093705 (2012) Holographic microrefractometer Appl. Phys. Lett. 101, 091102 (2012) Foucault imaging by using non-dedicated transmission electron microscope Appl. Phys. Lett. 101, 093101 (2012) Micro optical power meter for direct in situ measurement of light transmitted from microscopic systems and focused on micro-samples Rev. Sci. Instrum. 83, 083107 (2012) Additional information on Rev. Sci. Instrum.A microscope employing the characteristics of the reflection at the Brewster angle has been built for the study of first-order phase transitions in monolayers and the growth of two-dimensional domains without adding fluorescent impurities. It takes about 2.4 s to constitute an image.
Two types of isotropic disordered nonergodic states exist in colloidal suspensions: glasses and gels. The difference between the two is that the nonergodicity, or elasticity, of gel stems from the existence of a percolated network, while that of glass stems from caging effects. Despite this clear difference in the origin of nonergodicity, it is not straightforward to distinguish the two states in a clear manner. Taking a Laponite suspension as an explicit example, we propose a general phase diagram for charged colloidal systems. It follows that a transition from the glass to the gel state can be induced by changing the interparticle interactions from predominantly repulsive to attractive. This originates from the competition between electrostatic Coulomb repulsion and van der Waals attraction. If the repulsion dominates, the system forms a Wigner glass, while in a predominantly attractive situation it forms a gel. In the intermediate region, where both repulsive and attractive interactions play roles, it may form an attractive glass.
Solutions of the synthetic clay Laponite are strongly viscoelastic, even at very low particle concentrations. The formation of a gel, evidenced by the existence of a fractal network, has been invoked in explaining the viscoelasticity. We study the structure and viscosity of Laponite using static light scattering and rheometry. Contrary to previous observations, we find no evidence of a fractal-like organization of the colloidal particles, provided the dispersion is prepared carefully. The results show that there is no relation between the apparent fractal dimension and the viscoelasticity. A possible interpretation of our results is that Laponite solutions form colloidal glasses, rather than gels.
PACS. 64.70Pf -Glass transitions. PACS. 61.20Lc -Time-dependent properties; relaxation.Abstract. -We study the aging of a colloidal glass, which is obtained for extremely low volume fractions due to strong electrostatic repulsions, leading to the formation of a "Wigner glass". During the aging, a new crossover between a complete and incomplete decay of the correlation function is observed, accompanied by an increase in the non-ergodicity parameter. The dynamics can be described as a cage-diffusion process. For short times, the escape of the particles from "cages" formed by neighbouring particles dominates; for long times the particles cannot escape anymore and the system becomes strongly non-ergodic.Glasses are a non-equilibrium form of matter and are, maybe for that reason, still illunderstood [1][2][3][4]. The usual way of looking at the glass transition is given by the so-called schematic mode-coupling theory [1,2]. In this theory, the glass transition is a strong ergodic to non-ergodic transition. In real systems, however, the "transition" always appears rounded. The rounding of the transition is due to the appearance of a "slow mode" in the system [1-4]. The non-equilibrium evolution of a system quenched into a glassy state is often referred to as aging, and is common to both structural and spin-glasses. Understanding the aging processes in a glassy system is crucial for the description of glassy dynamics; unfortunately, due to its very nature, the classical mode-coupling theory does not provide us with any information on the aging process [2].A recent careful inspection of the mode-coupling equations [4] reveals that this serious limitation may in fact be overcome. This work presents the first detailed description of the aging process. The evolution of the system is described in terms of the correlation and response functions of the system. Unfortunately, for most of the systems (structural glasses) studied to date, these quantities are not easy to obtain experimentally. For this reason, progress has been limited to a number of recent theoretical (spin-glass) and simulation (Lennard-Jones glass) studies [3,4]. The key result of both theory and simulations is that the diffusion may be looked upon as a cage-diffusion process. The particles reside in dynamic cages formed by c EDP Sciences
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