Thibaut Charpentier

Development of anti-icing materials by chemical tailoring of hydrophobic textured metallic surfaces

Ice on surfaces can have dramatic consequences for human activities. Over the last decades, the design of new materials with anti-icing properties has generated significant research efforts for the prevention of ice accretion. Here we investigate water freezing temperatures on untreated and negatively charged hydrophobic stainless steel surfaces and use these temperatures to evaluate icephobicity. Supercooled water microdroplets are deposited and undergo a slow controlled cooling until spontaneous freezing occurs. Textured hydrophobic stainless steel surfaces functionalized with anionic polyelectrolytes brushes display unexpectedly lower freezing temperatures, at least 7 °C lower than polished untreated steel. On the basis of the entropy reduction of the crystalline phase near a charged solid surface, we used a modification of the classical heterogeneous nucleation theory to explain the observed freezing temperatures lessening. Our results could help the design of new composite materials that more efficiently prevent ice formation.

Preparation of Magnetic Carboxymethylchitosan Nanoparticles for Adsorption of Heavy Metal Ions

The remediation of metal and heavy metal contaminants from water ecosystems is a long-standing problem in the field of water management. The development of efficient, cost effective, and environmentally friendly natural polymer-based adsorbents is reported here. Magnetic chitosan (CS) and carboxymethylchitosan (CMC) nanocomposites have been synthesized by a simple one-step chemical coprecipitation method. The nanoparticles were assessed for the removal of Pb2+, Cu2+, and Zn2+ ions from aqueous solution. Kinetic and thermodynamic models were used to describe and understand the adsorption process of the ions onto the nanomaterials. The interactions between the ions and the biopolymer-based composites are reversible, which means that the nanoparticles can be regenerated in weakly acidic or EDTA containing solution without losing their activity and stability for water cleanup applications.

Liquid infused porous surfaces for mineral fouling mitigation

Prevention of mineral fouling, known as scale, is a long-standing problem in a wide variety of industrial applications, such as oil production, water treatment, and many others. The build-up of inorganic scale such as calcium carbonate on surfaces and facilities is undesirable as it can result in safety risks and associated flow assurance issues. To date the overwhelming amount of research has mainly focused on chemical inhibition of scale bulk precipitation and little attention has been paid to deposition onto surfaces. The development of novel more environmentally-friendly strategies to control mineral fouling will most probably necessitate a multifunctional approach including surface engineering. In this study, we demonstrate that liquid infused porous surfaces provide an appealing strategy for surface modification to reduce mineral scale deposition. Microporous polypyrrole (PPy) coatings were fabricated onto stainless steel substrates by electrodeposition in potentiostatic mode. Subsequent infusion of low surface energy lubricants (fluorinated oil Fluorinert FC-70 and ionic liquid 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIm)) into the porous coatings results in liquid-repellent slippery surfaces. To assess their ability to reduce surface scaling the coatings were subjected to a calcium carbonate scaling environment and the scale on the surface was quantified using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). PPy surfaces infused with BMIm (and Fluorinert to a lesser extent) exhibit remarkable antifouling properties with the calcium carbonate deposition reduced by 18 times in comparison to untreated stainless steel. These scaling tests suggest a correlation between the stability of the liquid infused surfaces in artificial brines and fouling reduction efficiency. The current work shows the great potential of such novel coatings for the management of mineral scale fouling.

An Investigation of Freezing of Supercooled Water on Anti-Freeze Protein Modified Surfaces

This work investigates how functionalization of aluminium surfaces with natural type III Anti-Freeze Protein (AFP) affects the mechanism of heterogeneous ice nucleation. First the bulk ice nucleation properties of distilled water and aqueous solution of AFP were evaluated by differential scanning calorimetry. Then the modified surface was characterized by Secondary Ions Mass Spectroscopy (SIMS), Fourier Transform InfraRed (FTIR) spectroscopy and contact angle measurement. Freezing experiments were then conducted in which water droplets underwent a slow controlled cooling. This study shows that compared to uncoated aluminium, the anti-freeze proteins functionalized surfaces exhibit a higher and narrower range of freezing tempera-ture. It was found that these proteins that keep living organisms from freezing in cold environment act in the opposite way once immobilized on surfaces by promoting ice nucleation. Some suggestions regarding the mechanism of action of the observed phenomena were proposed based on the Classical Nucleation Theory (CNT).

Evaluation of Anti-fouling Surfaces for Prevention of Mineral Scaling in Sub-surface Safety Valves

Mineral scale formation and deposition in down-hole completion equipment such as subsurface safety valves can cause dramatic and unacceptable safety risks and associated production losses and operational costs. Current scale removal strategies involve both mechanical and chemical technologies, each of them having their own advantages depending on the type of mineral scale and its location. However, these techniques are often costly and of limited efficiency. The current study assesses the ability of a range of chemically and morphologically modified coatings to prevent/reduce mineral scale surface fouling. Building-up on previous work done under static conditions, this paper presents results from scaling tests under laminar and turbulent dynamic conditions using a rotating cylinder electrode under in a complex (mixed) scaling environment (supersaturated w.r.t. calcium carbonate, barium sulfate, strontium sulfate, barium carbonate and strontium carbonate). The study shows that if properly selected, surface treatments represent a promising approach to reduce scale deposition on downhole equipment surfaces that are critical to maintain equipment functionality and thereby well safety barrier integrity. By analyzing the scaling behaviors observed within the set of surfaces tested, suggestions of the controlling factors in anti-fouling on these systems are presented and discussed.

Siderite micro-modification for enhanced corrosion protection

Production of oil and gas results in the creation of carbon dioxide (CO2) which when wet is extremely corrosive owing to the speciation of carbonic acid. Severe production losses and safety incidents occur when carbon steel (CS) is used as a pipeline material if corrosion is not properly managed. Currently corrosion inhibitor (CI) chemicals are used to ensure that the material degradation rates are properly controlled; this imposes operational constraints, costs of deployment and environmental issues. In specific conditions, a naturally growing corrosion product known as siderite or iron carbonate (FeCO3) precipitates onto the internal pipe wall providing protection from electrochemical degradation. Many parameters influence the thermodynamics of FeCO3 precipitation which is generally favoured at high values of temperatures, pressure and pH. In this paper, a new approach for corrosion management is presented; micro-modifying the corrosion product. This novel mitigation approach relies on enhancing the crystallisation of FeCO3 and improving its density, protectiveness and mechanical properties. The addition of a silicon-rich nanofiller is shown to augment the growth of FeCO3 at lower pH and temperature without affecting the bulk pH. The hybrid FeCO3 exhibits superior general and localised corrosion properties. The findings herein indicate that it is possible to locally alter the environment in the vicinity of the corroding steel in order to grow a dense and therefore protective FeCO3 film via the incorporation of hybrid organic-inorganic silsesquioxane moieties. The durability and mechanical integrity of the film is also significantly improved.Fuel pipelines: using corrosion to our advantageEngineering the FeCO3 films that form in gas and oil pipelines offers a cheap and environmentally friendly option for corrosion management. Thousands of kilometres of steel−based fuel transportation networks across the US and the UK require protection from wet and corrosive CO2, and current methods involve the expensive and environmentally-harmful deployment of corrosion inhibitor chemicals. A team led by Wassim Taleb at the University of Leeds in the UK show that adding a silicon-rich filler into the mix not only accelerates growth of the protective FeCO3 corrosion product on the internal pipe walls, but also enhances the strength and durability of these films, slowing the rate of further steel degradation. Being able to modify these films in a batch treatment could drastically change the way that corrosion is managed in fuel pipelines.

Using a Real-Time Visualisation Technique for the Assessment of Surface Scale Kinetics and Mechanisms of Inhibition

Improving the understanding of surface scale formation is important in implementing an effective scale management strategy in the oil and gas industry. Investigations into scale formation have largely been focused on precipitation in the bulk solution by assuming that surface scaling always results from pre-precipitated crystals in the bulk solution. However, recent studies have shown that scale inhibition efficiency and the effects on crystal morphology vary between surface and bulk processes The study is focused on the formation of BaSO4 and CaCO3 scale on stainless steel surface at constant saturation ratio (SR) using a visualization flow rig. The effects of SR, flow rates and temperature on surface scaling were studied. Also, the influence of SR and inhibitor concentration on surface inhibition efficiency of Polyphosphinocarboxylic acid (PPCA) and diethylenetriamine penta methylphosphonic acid (DETPMP) were studied. The range of SR considered is between 10 and 80 and with these values the experiments are conducted with no pre-precipitated crystals in the bulk solution. The flow rates used are between 10ml/min to 60ml/min. It is shown that the determination of surface crystallization mechanisms and kinetics allows for the correct type and dosage of inhibitor to be selected. Addition of inhibitors at the bulk minimum inhibition concentration (MIC) actually aggravates surface scaling. For a similar range of SR and test conditions, CaCO3 scale builds up on the surface shows the predominance of growth which results in bigger crystals and a smaller number of crystals while BaSO4 scaling results in a higher number of crystals nucleating from the surface asperities with slower growth rate and hence smaller crystals.

Comparison of characteristic of anti-scaling coating for subsurface safety valve for use in oil and gas industry

A subsurface safety valve is used to shut in a well automatically, if the wellhead equipment or other surface production equipment fails. It is almost always installed as a vital component on the completion. In many industrial systems, scale formation causes significant problems, not when it precipitates in bulk solution but when it deposits on the surface. Surface scaling is a complex phenomenon where several processes such as heterogeneous crystallization or particle adhesion are inextricably linked and occur simultaneously. The sub-surface safety valve can accumulate carbonate, sulphate and sulphide scale. Even a thin layer of scale can impede the smooth operation of the valve and pose serious regulatory and safety risks. In this study twenty coatings from seven different natures have been tested. These coatings are Fluoropolymers, Composite (fluotopolymer matrix), Sol-gel nano-coating, Textured hydrophobic paint, Diamond Like Carbon (DLC), Polished Inconel and Nitro carburated Inconel. Whilst the anti-scaling capability of the coating is the key functional element, it is extremely important that the coating presents other important parameters such as hydrophobicity property, surface roughness, coating thickness and hardness, resistance to erosion, corrosion and temperature as well as coating adhesion. In this paper the controlling factors of anti-scaling coatings are discussed. Promising coatings with anti-scaling properties have been identified.