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N. Panchev

Bio: N. Panchev is an academic researcher from Bulgarian Academy of Sciences. The author has contributed to research in topics: Emulsion & Wetting. The author has an hindex of 3, co-authored 5 publications receiving 104 citations.

Papers
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Journal ArticleDOI
TL;DR: It is shown that with increasing CTAB concentration a charge reversal occurs at both the solution/air and solution/quartz interfaces that determines the stability/instability of the foam and wetting films.

77 citations

Journal ArticleDOI
TL;DR: In this paper, a microinterferometric Thin Liquid Film-Pressure Balance Technique (TLBP) was used to study thin liquid emulsion films. But this technique is not suitable for the analysis of water-in-oil emulsions at a microscopic level.

20 citations

Journal ArticleDOI
TL;DR: In this article, a modification of TLF-PBT cell allows probing water-in-oil emulsion films with electrical signal, a new technique to study water inoil emulsions.

14 citations

Journal Article
TL;DR: In this article, a modification of TLF-PBT cell allows probing water-in-oil emulsion films with electrical signal, a new technique to study water inoil emulsions.

1 citations

Journal ArticleDOI
TL;DR: In this paper, the applicability of Vcr parameter for characterization of film stability as a function of concentration of real bitumen solutions, Cs, is investigated, and the equilibrium film thickness, h, corresponding to each bitumen concentration, is also monitored.

Cited by
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Journal ArticleDOI
TL;DR: The purpose of this review is to bring together the many experimental results on nanobubbles and the resulting capillary force in order to clarify these phenomena, and a review of pertinentnanobubble stability and formation theories is presented.

293 citations

Journal ArticleDOI
TL;DR: In this critical review, the recent research findings and progress in the interfacial sciences related to unconventional petroleum production are critically reviewed and the chemistry of unconventional oils, liberation mechanisms of oil from host rocks and mechanisms of emulsion stability and destabilization in unconventional oil production systems are discussed in detail.
Abstract: With the ever increasing demand for energy to meet the needs of growth in population and improvement in the living standards in particular in developing countries, the abundant unconventional oil reserves (about 70% of total world oil), such as heavy oil, oil/tar sands and shale oil, are playing an increasingly important role in securing global energy supply. Compared with the conventional reserves unconventional oil reserves are characterized by extremely high viscosity and density, combined with complex chemistry. As a result, petroleum production from unconventional oil reserves is much more difficult and costly with more serious environmental impacts. As a key underpinning science, understanding the interfacial phenomena involved in unconventional petroleum production, such as oil liberation from host rocks, oil–water emulsions and demulsification, is critical for developing novel processes to improve oil production while reducing GHG emission and other environmental impacts at a lower operating cost. In the past decade, significant efforts and advances have been made in applying the principles of interfacial sciences to better understand complex unconventional oil-systems, while many environmental and production challenges remain. In this critical review, the recent research findings and progress in the interfacial sciences related to unconventional petroleum production are critically reviewed. In particular, the chemistry of unconventional oils, liberation mechanisms of oil from host rocks and mechanisms of emulsion stability and destabilization in unconventional oil production systems are discussed in detail. This review also seeks to summarize the current state-of-the-art characterization techniques and brings forward the challenges and opportunities for future research in this important field of physical chemistry and petroleum.

263 citations

Journal ArticleDOI
TL;DR: It was observed that presence of a micro-bubble at the solid surface facilitated drastically an attachment of the colliding bubble, and roughness of Teflon surface increases probability of the bubble attachment-most probably-as a result of higher probability of micro- and/or nano-bubbles presence at theSolid surface.

218 citations

Journal ArticleDOI
01 Jun 2010-Langmuir
TL;DR: It is argued that the dramatic reduction in hydrodynamic resistance is a transition from viscosity-controlled drainage to inertia- controlled drainage associated with a change from immobile to mobile air/water interfaces on increasing the speed of approach of two bubbles.
Abstract: Film thinning experiments have been conducted with aqueous films between two air phases in a thin film pressure balance. The films are free of added surfactant but simple NaCl electrolyte is added in some experiments. Initially the experiments begin with a comparatively large volume of water in a cylindrical capillary tube a few millimeters in diameter, and by withdrawing water from the center of the tube the two bounding menisci are drawn together at a prescribed rate. This models two air bubbles approaching at a controlled speed. In pure water, the results show three regimes of behavior depending on the approach speed; at slow speed (<1 microm/s) it is possible to form a flat film of pure water, approximately 100 nm thick, that is stabilized indefinitely by disjoining pressure due to repulsive double-layer interactions between naturally charged air/water interfaces. The data are consistent with a surface potential of -57 mV on the bubble surfaces. At intermediate approach speed (approximately 1-150 microm/s), the films are transiently stable due to hydrodynamic drainage effects, and bubble coalescence is delayed by approximately 10-100 s. At approach speeds greater than approximately 150 microm/s, the hydrodynamic resistance appears to become negligible, and the bubbles coalesce without any measurable delay. Explanations for these observations are presented that take into account Derjaguin-Landau-Verwey-Overbeek and Marangoni effects entering through disjoining pressure, surface mobility, and hydrodynamic flow regimes in thin film drainage. In particular, it is argued that the dramatic reduction in hydrodynamic resistance is a transition from viscosity-controlled drainage to inertia-controlled drainage associated with a change from immobile to mobile air/water interfaces on increasing the speed of approach of two bubbles. A simple model is developed that accounts for the boundaries between different film stability or coalescence regimes. Predictions of the model are consistent with the data, and the effects of adding electrolyte can be explained. In particular, addition of electrolyte at high concentration inhibits the near-instantaneous coalescence phenomenon, thereby contributing to increased foam film stability at high approach speeds, as reported in previous literature. This work highlights the significance of bubble approach speed as well as electrolyte concentration in affecting bubble coalescence.

148 citations

Journal ArticleDOI
TL;DR: The variation of CMC values as a function of NaCl concentration obtained from the surface tension measurements and critical packing parameter (CPP) calculations show that spherical micelles, bilayer and rod like micells are formed in the rhamnolipid solutions as afunction of the Na Cl concentration.

131 citations