Advances in Colloid and Interface Science (v.217, #C)

Asphaltenes are considered to be the heaviest and most polar fractions of crude oils and are frequently implicated in problems encountered during production and refining as a result of phase separation. In recent years, considerable effort has been given to understanding the phase behaviour of these structurally heterogeneous materials from both experimental and computational perspectives. Various experimental studies have confirmed the long-advanced colloidal behaviour of asphaltenes in organic media, and this has inspired a number of modelling strategies. The present review is specifically concerned with advances in modelling asphaltene phase behaviour with emphasis on the use of the statistical associating fluid theory (SAFT), which it attempts to place into the wider context of thermodynamic treatments.Display Omitted
Keywords: Asphaltene; Phase behaviour; Modelling; Equations of state; SAFT;

Sessile nanofluid droplet drying by Xin Zhong; Alexandru Crivoi; Fei Duan (13-30).
Nanofluid droplet evaporation has gained much audience nowadays due to its wide applications in painting, coating, surface patterning, particle deposition, etc. This paper reviews the drying progress and deposition formation from the evaporative sessile droplets with the suspended insoluble solutes, especially nanoparticles. The main content covers the evaporation fundamental, the particle self-assembly, and deposition patterns in sessile nanofluid droplet. Both experimental and theoretical studies are presented. The effects of the type, concentration and size of nanoparticles on the spreading and evaporative dynamics are elucidated at first, serving the basis for the understanding of particle motion and deposition process which are introduced afterward. Stressing on particle assembly and production of desirable residue patterns, we express abundant experimental interventions, various types of deposits, and the effects on nanoparticle deposition. The review ends with the introduction of theoretical investigations, including the Navier–Stokes equations in terms of solutions, the Diffusion Limited Aggregation approach, the Kinetic Monte Carlo method, and the Dynamical Density Functional Theory. Nanoparticles have shown great influences in spreading, evaporation rate, evaporation regime, fluid flow and pattern formation of sessile droplets. Under different experimental conditions, various deposition patterns can be formed. The existing theoretical approaches are able to predict fluid dynamics, particle motion and deposition patterns in the particular cases. On the basis of further understanding of the effects of fluid dynamics and particle motion, the desirable patterns can be obtained with appropriate experimental regulations.Display Omitted
Keywords: Nanofluid; Sessile droplet; Evaporative dynamics; Drying patterns;

Measurement and modeling on hydrodynamic forces and deformation of an air bubble approaching a solid sphere in liquids by Mansoureh Shahalami; Louxiang Wang; Chu Wu; Jacob H. Masliyah; Zhenghe Xu; Derek Y.C. Chan (31-42).
The interaction between bubbles and solid surfaces is central to a broad range of industrial and biological processes. Various experimental techniques have been developed to measure the interactions of bubbles approaching solids in a liquid. A main challenge is to accurately and reliably control the relative motion over a wide range of hydrodynamic conditions and at the same time to determine the interaction forces, bubble–solid separation and bubble deformation. Existing experimental methods are able to focus only on one of the aspects of this problem, mostly for bubbles and particles with characteristic dimensions either below 100 μm or above 1 cm. As a result, either the interfacial deformations are measured directly with the forces being inferred from a model, or the forces are measured directly with the deformations to be deduced from the theory. The recently developed integrated thin film drainage apparatus (ITFDA) filled the gap of intermediate bubble/particle size ranges that are commonly encountered in mineral and oil recovery applications. Equipped with side-view digital cameras along with a bimorph cantilever as force sensor and speaker diaphragm as the driver for bubble to approach a solid sphere, the ITFDA has the capacity to measure simultaneously and independently the forces and interfacial deformations as a bubble approaches a solid sphere in a liquid. Coupled with the thin liquid film drainage modeling, the ITFDA measurement allows the critical role of surface tension, fluid viscosity and bubble approach speed in determining bubble deformation (profile) and hydrodynamic forces to be elucidated. Here we compare the available methods of studying bubble–solid interactions and demonstrate unique features and advantages of the ITFDA for measuring both forces and bubble deformations in systems of Reynolds numbers as high as 10. The consistency and accuracy of such measurement are tested against the well established Stokes–Reynolds–Young–Laplace model. The potential to use the design principles of the ITFDA for fundamental and developmental research is demonstrated.Display Omitted
Keywords: Direct force measurements; Hydrodynamic forces; Bubble–solid interactions; Film drainage; Interfacial deformations;

The interface between fibre and matrix of fibrous polymeric composites is most critical and decisive in maintaining sustainability, durability and also reliability of this potential material, but unfortunately a comprehensive conclusion is yet to meet the label of confidence for the engineering viability. Fiber reinforced polymer (FRP) composites are being accepted and also utilized as better and reliable alternative materials for repairing and/or replacing conventional materials, starting from tiny objects to mega structure in various engineering applications. The promise and potential of these materials are sometimes threatened in speedy replacement of conventional materials because of their inhomogeneities and inherent susceptibility to degradation due to moist and thermal environments. Environmental conditioning is traditionally believed to be a physical phenomenon but present literature has revealed that the interdiffusion between fiber and polymer matrix resin comprises of physical, chemical, mechanical, physico-chemical and mechano-chemical phenomena. The failure and fracture behavior at ambient conditions itself is a complex phenomenon till at present. The service conditions which are mostly hygrothermal in nature, along with a variation of applied loads make the mechanical behavior nearly unpredictable, far off from conclusions in evaluating the short term as well as long term durability and reliability of FRPs. It is essential to accurately simulate the initial and subsequent evolution process of this kind of damage phenomena, in order to explore the full potential of the mechanical properties of composite laminates. The present review has emphasized the need of complying scattered as well as limited literature on this front, and has focused on creating the urgency to highlight the importance of judicious uses of these materials with minimum safety factors with an aim to achieving lighter weight in enhancing specific properties.The percentage of ILSS value decreases during above-ambient temperature testing in every mode of loading rate ranges because of thermal conditioning effect leading to spreading of process zone in the matrix resin which imparts high fibre/matrix debonding in glass/epoxy composites shown in the figure below.The changes occurring at the interface are highly sensitive and susceptible to the degradations under different environmental conditionings. Since the interphase is a region of chemical inhomogeneity, it provides an easy path to the system for becoming more susceptible to thermal, chemical, thermochemical and mechano-chemical degradations.Display Omitted
Keywords: Polymer matrix composites; Environmental degradation; Fiber/matrix interface; Failure modes; Physico-chemical phenomena; Mechano-chemical phenomena;