Study On Surface Wettability Based On OIRD Technology

Wetting is one of the most common natural phenomena in nature and wettability is an essential characteristic of material surfaces that is relevant to human life.As a popular topic in materials science,the study of wettability not only helps to understand surface phenomena and improve the performance of materials,but also provides a powerful impetus to other areas of development.To date,wettable materials have been used in various fields in academia,industry,agriculture,and biomedical engineering.With the growing interest in wettability,there has been a great deal of research into it by various technical means.However,many of the interfacial issues involved in the wetting process have not been fully resolved.For example,although the wetting system is constantly being improved,there is still a lack of clear theoretical and methodological explanations for the three-phase lines at the solid-liquid-gas interface during the wetting process.The nanoscale interactions,molecular dynamics,and energy transfer at the solid-liquid interface during the wetting process.And there need more reasonable theoretical models to explain the relationship between the three-phase lines and the apparent contact angle on special wetting surfaces.In-situ,non-destructive nanoscale imaging techniques led by the study of three-phase lines also need to be investigated in-depth to obtain further information on the solid-liquid-gas interface.The oblique-incidence reflectivity difference(OIRD)technology has now been applied to a number of fields such as real-time in situ monitoring of film growth,identification and detection of biomolecules and related reaction processes in highthroughput microarrays,characterization and analysis of oil and gas reservoir potential due to its advantage of being very sensitive to surface properties.It has good prospects for application in the field of wettability.This thesis analyzed the feasibility of evaluating wettability characterization using the Oblique-incidence reflectivity difference technique as the primary research tool,and investigated the adsorption process of surfactants on mica surfaces.The main research results are as follows:(1)The signal response characteristics of OIRD for dynamic changes in fluid surface shape were clarified.Using the OIRD technique detected the shape of the liquid surface during dynamic changes.The results show that the signal response characteristics of the OIRD when the liquid surface changes have a clear directionality.The signal peaks distribute on the left side when the liquid surface is convex,and the signal is weaker the smaller the radius of curvature of the liquid surface.The signal peaks distribute on the right side when the liquid surface is concave,and the signal is weaker the smaller the radius of curvature of the liquid surface.(2)There Clarifies a physical model for the qualitative evaluation of wettability by OIRD.The two-dimensional image of the OIRD clearly visualizes the shape,position,and size of the contact lines of the solid oil droplets on the four different surfaces.The signal waveforms also reflect the variation of the droplet contact angle.Meanwhile,the three-dimensional images of oil droplets on four surfaces show different peak shapes.The larger the apparent contact angle of the oil droplets,the more oleophobic the substrate surface is,and the smoother the signal’s peak in the 3D image of OIRD.The smaller the apparent contact angle of the oil droplets,the less oleophobic the substrate surface is,and the sharper the signal’s peak in the 3D image.The results suggest that the OIRD technique can qualitatively evaluate surface wettability.(3)There elucidated the mechanism of surfactant adsorption on mica surfaces.Surfactants are a widely used surface wetting modifier.The study of surfactant adsorption behavior on mineral surfaces is important to interfacial science and plays an essential role in enhancing the recovery of oil and gas resources.This paper conducted real-time,in situ OIRD tests on the adsorption processes of three ionic surfactants,sodium lauryl sulfate(SDS),sodium dodecylbenzene sulfonate(SDBS),and cetyl trimethyl ammonium bromide(CTAB)on mica.And obtain the response characteristics of the OIRD signal during the adsorption process.Combined with the principle of OIRD detection,the variation of adsorption layer thickness and relative dielectric constant can be deduced,thus clarifying the adsorption mechanism of the three surfactants on mica.That is,the active agent molecules adsorbed on the mica surface will change from a monolayer structure in the form of single molecules to a multilayer structure composed of micelles and semi-micelles as the surfactant concentration increases.The hydrophobic nature of the outermost layer of the adsorbent layer gives the mica surface a different wettability.(4)The relative dielectric constants of the adsorbed layers were obtained.Using the experimentally measured real and imaginary signals of OIRD as parameters,the relative permittivity of the adsorbed layer for different concentrations of SDS adsorbed on the mica surface was obtained according to the three-layer model equation for oblique incident light reflection difference.It provides a theoretical reference for studying the interfacial charge distribution and the change of surface energy of the material.