Investigation of calcium carbonate precipitated in the presence of alkanols

The influence of myristyl alcohol (CH₃(CH₂)₁₃OH), cetyl alcohol (CH₃(CH₂)₁₅OH) and behenyl alcohol (CH₃(CH₂)₂₁OH) on the structure, morphology, size and surface properties of calcium carbonate (CaCO₃) has been investigated. Changes in the nature of the washing solvent, in the C_nOH/Ca²⁺ and CO₃²⁻/Ca²⁺ molar ratios and in temperature have been also evaluated. The sole polymorph produced was rhombohedral calcite. At room temperature, while microspheres composed of submicrocubes were produced at a high molar ratio CO₃²⁻/Ca²⁺ and low CH₃(CH₂)₁₅OH concentration, a stoichiometric molar ratio CO₃²⁻/Ca²⁺ and high CH₃(CH₂)₁₅OH concentration induced the formation of microcubes and microboxes. In the presence of this alkanol (12 % molar) a significant enhancement of the water contact angle (ca. 40 °) resulted in a sample obtained with a stoichiometric CO₃²⁻/Ca²⁺ ratio. These results emphasize the key role played by the three non‐ionic surfactants in the formation of materials with variable crystal shape and wettability and thus technological interest for a range of applications.     

双尺度疏油结构纳米通道滑移效应的研究

针对双尺度结构表面疏油特性的优异性,采用分子动力学的方法建立油液流体正十六烷烃分子模型,研究双尺度结构壁面润湿性影响下的纳米通道内流体的流动特性,通过对通道壁面亲疏油性下的双尺度结构的构建,与光滑壁面和单尺度壁面进行比较来探究双尺度纳米通道表面结构影响下油液流体在纳米通道内密度分布、速度分布、速度滑移和滑移长度的影响.模拟结果表明:对于亲油通道壁面,双尺度结构壁面亲油性明显加强,主流区域流体密度、流体速度和速度滑移都减小,甚至出现负滑移;而对于疏油通道壁面,双尺度分层结构能加强壁面的疏油性,通道内壁面形成稳定的气层使流体主流区域的密度增大,并且通道内流体的速度、速度滑移和滑移长度明显大于光滑和单尺度结构壁面.因此,纳米通道内双尺度结构能改变通道壁面的润湿性,并且能够加强流体在纳米疏油通道内的滑移减阻效应,为纳米通道内油液运输以及润滑薄膜减阻提供了设计基础.     

Osteoblast cell response to a CO2 laser modified polymeric material

Lasers are an efficient technology, which can be applied for the surface treatment of polymeric biomaterials to enhance insufficient surface properties. That is, the surface chemistry and topography of biomaterials can be modulated to increase the biofunctionality of that material. By employing CO₂ laser patterning and whole area processing of nylon 6,6 this paper details how the surface properties were significantly modified. Samples, which had undergone whole area processing, followed the current theory in which the advancing contact angle, θ, with water decreased and the polar component, γ^p, increased upon an increase in surface roughness. For the patterned samples it was observed that θ increased and γ^P decreased. This did not follow the current theory and can be explained by a mixed-state wetting regime. By seeding osteoblast cells onto the samples for 24 h and 4 days the laser surface treatment gave rise to modulated cell response. For the laser whole area processing, θ and γ^P correlated with the observed cell count and cover density. Owed to the wetting regime, the patterned samples did not give rise to any correlative trend. As a result, CO₂ laser whole area processing is more likely to allow one to predict biofunctionality prior to cell seeding. Moreover, for all samples, cell differentiation was evidenced. On account of this and the modulation in cell response, it has been shown that laser surface treatment lends itself to changing the biofunctional properties of nylon 6,6.     

Surface modification of poly(styrene-b-(ethylene-co-butylene)-b-styrene) elastomer via photo-initiated graft polymerization of poly(ethylene glycol)

Poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) copolymer biomedical elastomer was covalently grafted with poly(ethylene glycol) methyl ether methacrylate (PEGMA) via a photo-initiated graft polymerization technique. The surface graft polymerization of SEBS with PEGMA was verified by ATR-FTIR and XPS. Effect of graft polymerization parameters, i.e., monomer concentration, UV irradiation time and initiator concentration on the grafting density was investigated. Comparing with the virgin SEBS film, the PEGMA-modified SEBS film presented an enhanced wettability and a larger surface energy. Besides, the surface grafting of PEGMA imparted excellent anti-platelet adhesion and anti-protein adsorption to the SEBS surface.     

Wetting Phase Bridges Establish Capillary Continuity Across Open Fractures and Increase Oil Recovery in Mixed-Wet Fractured Chalk

The effect of fractures on oil recovery and in situ saturation development in fractured chalk has been determined at near neutral wettability conditions. Fluid saturation development was monitored both in the matrix and in the fractures and the mechanisms of fracture crossing were determined using high spatial resolution MRI. Capillary continuity across open oil-filled fractures was verified by imaging the water bridges established within the fracture. Despite an alternate escape fracture for the water, separate water bridges were shown to be stable for the entire duration of the experiments. The established capillary contact resulted in oil recovery exceeding the spontaneous imbibition potential in the outlet-isolated cores by ca. 10% PV. This is explained by viscous recovery provided by water bridges across open fractures. The size of the bridges seemed to be controlled by the wettability of the rock and not by the differential pressure applied across the open fracture.     

Spreading of inkjet droplet of non-Newtonian fluid on solid surface with controlled contact angle at low Weber and Reynolds numbers

The dynamics of inkjet droplet of non-Newtonian fluid on glass substrates was investigated experimentally and compared with that of Newtonian fluid. The non-Newtonian fluids used here were 100 ppm solutions of polyethylene oxide (300k, 600k and 900k) dissolved in the 1:1 mixture of water and glycerin. Weber number (We) was 2–35 and Ohnesorge number was fixed at 0.057 ± 0.003. The wettability of solid substrate was also varied. The diameter of inkjet droplets in the present study was about 50 μm and was much smaller than the size of the previous studies on drop impact. Due to the development of a thin and long thread at the rear of the main drop the jetting window of polymer solution was much narrower than that of Newtonian fluid, and hence the experimental range of Weber number was restricted. The impact scenarios of non-Newtonian inkjet droplets were found to be qualitatively different from those of Newtonian droplets during the receding phase while they were almost the same as the Newtonian fluid case during the kinematic phase. The spreading diameter at the equilibrium was well correlated with the modified Weber number (We′ = We/(1 − cos θ_eq)) as in the case of Newtonian fluid, where θ_eq is the equilibrium contact angle. The similarity or disparity between the Newtonian and non-Newtonian cases was discussed considering the conformation of polymer chains during each stage of drop deformation.     

光响应性超疏水偶氮苯自组装多层膜的制备及性质研究

近年来,偶氮苯类化合物的光学顺反异构现象已引起人们的广泛关注[1~7].在紫外光照射下,偶氮苯由反式结构转变为顺式结构,引起分子的偶极矩发生变化,导致分子的吸收光谱、尺寸及表面能等均发生变化[7].偶氮苯表面能的改变可引起其表面浸润性发生变化.据文献[1~4]报道,偶氮苯膜在紫外光照射前后接触角最大改变了11°.浸润性是固体表面的一个重要特性,主要受固体表面的化学组成和微观几何结构(粗糙度)影响[8~11].通常,与水的接触角大于150°的表面称为超疏水表面;而与水的接触角小于5°的表面称为超亲水表面.本文以2-(4-偶氮苯基苯氧基)丙烯酸…     

Potential-induced wetting and dewetting in hydrophobic nanochannels for mass transport control

Wetting and dewetting transitions play a central role in controlling the hydrophobicity of the lining of biological channels in order to regulate aqueous solution permeation. Understanding of the operational characteristics of biological nanochannels led to experimental efforts to mimic their behavior and to achieve potential-induced, repeatedly-switchable wettability transitions in synthetic nanochannels in the early 2010s. Since then, research has identified conditions needed to produce reversible wettability transitions using a number of different environmental stimuli—such as light, pH, and electrostatic charge—in addition to potential. Furthermore, nascent understanding of the underlying phenomena in synthetic nanochannels was rapidly followed by practical applications, including oil–water separations, drug release, and electroactive flow control based on switchable wettability. More practical applications are being developed continuously, as the physical and chemical principles that govern hydrophobic gating at the nanoscale are further elucidated, making it possible to exploit wettability as a design element in nanofluidic systems.     

Wetting and dewetting behaviour of hygroscopic liquids: Recent advancements

This review covers the most recent researches on wetting and dewetting phenomena related to the application of hygroscopic liquids in industry and technologies. Hygroscopic liquids actively absorb moisture from the surrounding air; therefore, they are used in the processes required for the moisturizing of surfaces or preventing the icing as well as control of evaporation rate and the humidity. The air humidity and wettability of substrates were shown to be crucial parameters affecting the wetting/dewetting kinetics of hygroscopic liquids. It is the adsorption of moisture on the hydrophilic surface that promotes the formation and spread of the precursor layer. The latter, in turn, is the droplet-spreading driver. The absorption of moisture by the liquid itself gives only a slight effect on wetting. The work devoted to the dewetting of hygroscopic liquids during evaporation, and the influence of thermal effects arising from contact with moist air on the wetting kinetics is also considered.     

Rheological properties of suspensions of polyethylene-coated aluminum nanoparticles

Ultrafine aluminum powder was identified as very promising fuels for novel energetic materials formulations. However, the large specific surface area of this powder facilitates its oxidation and greatly reduces its shelf life. Therefore, different coating processes were proposed to solve this problem. The rheology of viscous suspensions of nanoparticles still remains poorly understood and the effect of the coating of such particles on the flow behavior is even more difficult to assess. We have studied the rheology of ultrafine aluminum suspensions in three low molecular weight polymers of different viscosities: a hydroxy-terminated polybutadiene, a polypropylene glycol, and a polysiloxane. The nanosize aluminum powder was previously coated by a thin layer of high-density polyethylene using an in situ polymerization process. The rheological characterization of the suspensions was conducted by the means of steady and oscillatory shear flow measurements for noncoated and coated particles. The effect of the coating process on the rheology of the suspensions is discussed in terms of the interactions between the particles and the suspending fluids.