Nonpolymeric Coatings of Iron Oxide Colloids for Biological Use as Magnetic Resonance Imaging Contrast Agents

Iron oxide nanoparticles are used in vivo as contrast agents in magnetic resonance imaging. Their widely used polymer coatings are directly involved in their biocompatibility and avoid magnetic aggregation. As these polymer brushes also limit their tissular diffusion due to important hydrodynamic sizes, this work looks to obtain particles coated with thin layers of organic biocompatible molecules. Coating molecules were chosen depending on their fixation site on iron cores; carboxylates, sulfonates, phosphates, and phosphonates, and, among them, analogs of the phosphorylcholine. Two coating procedures (dialysis and exchange resins purification) were evaluated for hydrodynamic size, total iron concentration, electrophoretic mobility, and colloidal stability. Furthermore, a complementary test on stainless steel plates evaluated the contamination by competition of phosphonates as a rough estimation of the biocompatibility of the particles. Coating with bisphosphonates, the more interesting fixation moiety, leads to small (less than 15 nm) and stable objects in a wide range of pH including the neutrality. From stability data, the coating density was evaluated at around 1.6 molecules per nm(2). Including a quaternary ammonium salt to the coating molecule lowers their electrophoretic mobility. Moreover, this type of coating protects steel plates against contamination without significant desorption. All these properties allow further developments of these nanoparticles for biomedical applications. Copyright 2001 Academic Press.     

Synthesis and Properties of Cerium and Titanium Oxide Thin Coatings for Corrosion Protection of 304 Stainless Steel

Powders and thin coatings of ceria and titania were synthesized from aqueous and solvent-based precursors. Thin coatings were deposited on polished 304 stainless steel coupons by dipping them in the appropriate sol-gel oxide precursors. The coatings were subsequently densified and crystallized at several hundreds of degrees. It was possible to obtain dense titania coatings by applying thin coatings of cerium dioxide prior to titania on stainless steel substrates. Underlayer ceria coatings proved to be pivotal in obtaining dense titania coatings and preserving the integrity of the stainless steel while going through the high temperature treatments. The effect of processing parameters such as the atmosphere of heat-treatment, and temperature on the microstructure and crystal structure of the films and powders of ceria and titania was investigated. X-ray diffraction was used to identify the crystal structure of films and powders upon heat-treatment. Electrochemical measurements in NaCl, and analytical techniques such as SEM and EDX were used to evaluate the corrosion performance and pitting morphology of coated samples. A composite coating of ceria and titania was able to prevent crevice corrosion and increase the pitting resistance of the 304 stainless steel relative to the uncoated substrate.     

Molecularly imprinted polymer coated on stainless steel fiber for solid-phase microextraction of chloroacetanilide herbicides in soybean and corn

A molecularly imprinted polymer (MIP) with metolachlor as template was firstly coated on stainless steel fiber through chemical bonding strategy to solve the fragility problem of silica fiber substrate for solid-phase microextraction. The surface pretreatment of stainless steel fiber and the polymerization conditions were investigated systematically to enhance the preparation feasibility and MIP coating performance, and then a porous and highly cross-linked MIP coating with 14.8-μm thickness was obtained with over 200 times re-usability which was supported by non-fragile stainless steel fiber adoption. The MIP coating possessed specific selectivities to metolachlor, its metabolites and other chloroacetanilide herbicides with the factors of 1.1–4.6. Good extraction capacities of metolachlor, propisochlor and butachlor were found with MIP coating under quick adsorption and desorption kinetics, and the detection limits of 3.0, 9.6 and 38 μg L⁻¹ were achieved, respectively. Moreover, the MIP-coated stainless steel fiber was evaluated for trace metolachlor, propisochlor and butachlor extraction in the spiked soybean and corn samples, and the enrichment factors of 54–60, 27–31 and 15–20 were obtained, respectively.     

High-frequency electropulse deposition of microcrystallized MGH754 ODS alloy coatings

A simple but more efficient technique——high-frequency electropulse deposition——wasdeveloped to produce microcrystallized MGH754 ODS alloy coatings on the 1Cr18Ni9Ti stainless steel substrate. The coating has a very fine grain size of 30—300 nm and metallurgical bonding with the substrate. Isothermal oxidation in air at 1 000℃ for 100 h shows that micro-crystallisation and dispersed oxide particles promote the selective oxidation of Cr greatly to form a protective and continuous Cr2O3 scale and also improve the scale spallation resistance dramatically, thus increasing the oxidation resistance of 1Cr18Ni9Ti.     

Protective coatings based on Mn-Co spinel for current collectors of solid oxide fuel cells

The method of electrostatic spray pyrolysis was designed to apply protective coatings based on Mn-Co spinel to ferrite stainless steels (Crofer22APU and 08Kh18T1). The comparative thermogravimetric (TG) studies of ferrite stainless steels with and without protective coatings were carried out. The electrochemical characteristics of protective coatings exposed to long current loading were studied. The formation processes of Cr₂O₃ oxide films were studied at the contact of ferrite stainless steel with La_0.8Sr_0.2MnO₃ ionic and electronic conductor. The coatings of Mn-Co spinel were shown not preventing formation of continuous oxide film on the stainless steel surface.     

Improvement of Corrosion Resistance of Metals by an Environmentally Friendly Silica Coating Method

Corrosion resistance of stainless steel and Zn plated steel can be improved by a chromium-free environmentally friendly chemical solution deposition method. Precursor solutions were prepared from tetraethoxysilane with polymer, and were deposited on stainless steel, Zn plated steel and aluminum alloy by dip coating, followed by heat treatment. Addition of polymer to the precursor solution proved very effective in preparing films free from cracks on stainless steel and aluminum alloy substrates. The corrosion resistance was greatly improved by the resulting sub-micron thick silica-polymer hybrid film coatings on stainless steel and on Zn plated steel prepared at 200°C. The hardness of aluminum alloy coated with silica-PMMA hybrid film was improved by 7% over uncoated alloy.     

Polypyrrole films electrosynthesized on stainless steel grid from saccharinate aqueous solution and its behaviour toward acetone vapor

The electrochemical behaviour of stainless steel electrode in 0.1 M sodium saccharinate solution in the absence and the presence of the monomer were investigated using several electrochemical techniques such as cyclic voltammetry, galvanostatic and potentiostatic. The XPS analysis was used to study the elementary composition of the obtained polymer and to estimate the doping level of the PPy obtained under this electrolytic conditions. Moreover, the characterization of the coating was achieved by SEM, IR and Raman. In this context, samples of PPy in oxidized and reduced state synthesized galvanostatically on stainless steel grid were used to investigate the behaviour of the polymer toward acetone vapor.     

The electron microanalyzer (EPMA): a powerful device for the microanalysis of filled polymeric materials

The electron probe microanalyzer is a device often used in the field of geology or in the glass and steel industries. However, it is barely known or used in the polymer field. Thus, in this paper, we investigate the use of electron probe microanalyzer for polymer microanalyses and compared it with a scanning electron microscope equipped with an energy dispersive spectrometer. To show the unique potential of this technique only develop in our lab for polymer application, three different samples were studied: (i) a fire protective epoxy‐based coating submitted to aging in salt water, (ii) the distribution of organometallic catalysts into a thermal isolative silicone polymer, and (iii) the fouling growth of milk protein (biopolymer) on a stainless steel surface. Compared to an energy dispersive spectrometer, with an electron probe microanalyzer it is possible to quickly create X‐ray mappings of low concentration elements at a good resolution, as well as allowing the interpretation of the mechanism of action for the three samples which was impossible using only an energy dispersive spectrometer because of its too low detection resolution. Copyright © 2015 John Wiley & Sons, Ltd.     

Oxide film formation and diffusion processes in near-surface layers of current collectors in solid oxide fuel cells

A method is developed for modifying the surface of current collectors in solid-oxide fuel cells (SOFC) prepared from ferrite stainless steel (Crofer22APU). Diffusion of the protective coating material into the Crofer22APU bulk and reverse diffusion of steel components into the coating are studied. The cross-sectional microstructure and composition are studied by the electron-microscopic technique. The elemental composition of the junction between the current collector and the lanthanum-strontium manganite cathode is studied depending on the time of service-life tests in the SOFC working mode (50–6000 h). The formation of the Cr₂O₃ oxide islet structure on the current collector surface at the steel/coating interface is observed. It is shown that the mutual diffusion of coating components (Ni) and Crofer22APU steel together with the redox reaction at the interface prevent the chromium diffusion to the surface and protect the steel current collector from oxidation.     

Electrochemical preparation of zinc oxide/polypyrrole nanocomposite coating for the highly effective solid‐phase microextraction of phthalate esters

In this work, zinc oxide/polypyrrole nanocomposite coating was fabricated on stainless steel and evaluated as a novel headspace solid‐phase microextraction fiber coating for extraction of ultra‐trace amounts of environmental pollutants, namely, phthalate esters, in water samples. The fiber nanocomposite were prepared by a two‐step process including the electrochemical deposition of polypyrrole on the surface of stainless steel in the first step, and electrochemical deposition of zinc oxide nanosheets in the second step. Porous structure together with zinc oxide nanosheets with the average diameter of 30 nm were observed on the surface by using scanning electron microscopy. The effective parameters on extraction of phthalate esters (i.e., extraction temperature, extraction time, desorption temperature, desorption time, salt concentration, and stirring rate) were investigated and optimized by one‐variable‐at‐a‐time method. Under optimized conditions (extraction temperature, 90°C; extraction time, 40 min; desorption temperature, 270°C; desorption time, 5 min; salt concentration, 25% w/v; and stirring rate, 1000 rpm), the limits of detection were in the range of 0.05–0.8 μg/L, and the repeatability and fiber‐to‐fiber reproducibility were in the ranges of 6.1–7.3% and 8.7–10.2%, respectively.     

Preparation and Characterization of Metolachlor Molecularly Imprinted Polymer Coating on Stainless Steel Fibers for Solid-Phase Microextraction

A molecularly imprinted polymer (MIP) with metolachlor as the template molecule was first coated on the surface of stainless steel fibers through chemical bonding. Despite 12 times repeated coating procedures, a homogenous, porous, and highly cross-linked MIP coating was obtained with thickness of 17.4 µm (RSD of 6.1%). The specific selectivity of MIP coating to metolachlor and three metabolites could be concluded with 4.4, 4.1, 3.9, and 2.9 times higher extraction amounts of metolachlor, hydroxymetolachlor, deschlorometolachlor, and desmethylmetolachlor than that of the NIP coating, respectively, and good extraction capabilities for chloroacetanilide herbicides were found with the MIP-coated SPME stainless steel fiber. For validation, the fiber was applied for the extraction of metolachlor, propisochlor, and butachlor in spiked corn and soybean samples, and the recoveries of 90.7–92.6%, 86.4–87.9, and 85.4–87.5% were obtained, respectively.     

Analysis of corrosion layers on protective coatings and high temperature materials in simulated service environments of modern power plants using SNMS,SIMS, SEM,TEM, RBS and X-ray diffraction studies

In three different examples, the effects of the oxidation behaviour as well as the microstructural stability of high temperature materials and protective coatings was determined by combining the results of kinetic studies with extensive analytical investigations using, among other techniques, SNMS, SIMS, SEM, TEM, Rutherford back scattering (RBS) as well as X-ray diffraction. 1). The effect of water vapour on the oxidation behaviour of 9% Cr steels in simulated combustion gases has been determined. The effects of O2 and H2O content on the oxidation behaviour of 9% Cr steel in the temperature range 600-800 degrees C showed that in dry oxygen a protective scale was formed with an oxidation rate controlled by diffusion in the protective scale. In the presence of water vapour, after an incubation period, the scales became non-protective as a result of a change in the oxidation limiting process. The destruction of the protective scale by water vapour does not only depend on H2O content but also on the H2O/O2-ratio. 2). The increase of component surface temperature in modern gas turbines leads to an enhanced oxidation attack of the blade coating. Improvements in corrosion resistance and longer lifetime thermal barrier coatings in gas turbines have been achieved by improvement of the high temperature properties of MCrAlY coatings by additions of minor alloying elements such as yttrium, silicon and titanium. 3). The use of oxide dispersion strengthened (ODS) alloys provides excellent creep resistance up to much higher temperatures than can be achieved with conventional wrought or cast alloys in combination with suitable high temperature oxidation/corrosion resistance. Investigation of the growth mechanisms of protective chromia and alumina scales were examined by a two-stage oxidation method with 18O tracer. The distribution of the oxygen isotopes in the oxide scale was determined by SIMS and SNMS. The results show the positive influence of a Y2O3 dispersion on the oxidation resistance of the ODS alloys and its effect on growth mechanisms.     

Preparation of temperature sensitive molecularly imprinted polymer for solid-phase microextraction coatings on stainless steel fiber to measure ofloxacin

A kind of new temperature sensitive molecularly imprinted polymer (MIP) with ofloxacin (OFL) as template was prepared for the coating of solid phase microextraction (SPME). Dopamine was self-polymerized on stainless steel fiber (SSF) as the SPME support followed by silanization. Then MIP was synthesized as SPME coating on the modified SSF in a capillary, with N-isopropyl acrylamide as temperature sensitive monomer and methacrylic acid as functional monomer. The synthesis could be well repeated with multiple capillaries putting in the same reaction solution. The obtained MIP fiber was evaluated in detail with different techniques and various adsorption experiments. At last the MIP fiber was used to extract the OFL in milk. Satisfied recoveries between 89.7 and 103.4% were obtained with the limit of quantification (LOQ_LC) of 0.04 μg mL⁻¹ by the method of SPME coupled with high performance of liquid chromatography (HPLC).     

Electroactive conducting polymers for corrosion control

This paper reviews the literature describing the effects of conducting polymer coatings on the corrosion rate of ferrous alloys (iron, steel and stainless steel). The literature is interpreted in terms of the proposed mechanisms of corrosion protection: barrier, inhibitor, anodic protection and the mediation of oxygen reduction. The most intriguing aspect of the reported literature are the studies demonstrating corrosion protection when deliberate defects were introduced into the coating to expose the bare metal. These studies show that protection afforded by conducting polymer coatings is not due to simple barrier protection or inhibition alone. Many studies illustrate that the polymer/metal interface is modified to produce passivating oxide layers and that charge transfer reactions occur between the metal and polymer. These studies support the proposed anodic protection mechanism, as do the reports of significant ennoblism. On the other hand, there is considerable variation in the reported shift in corrosion potential and these highlight the influence of substrate preparation, coating composition and mode of application and the nature of the electrolyte on the corrosion protection provided by the conducting polymer. For example, the evidence suggests that the emeraldine base form of polyaniline is superior to the emeraldine salt in terms of corrosion protection for steel. However, the number of direct comparisons is small and the reasons for the differences are not well understood. Also not well understood are the role of the counterion release and local pH changes on pinhole protection. It is also argued that the conducting polymer reduces the likelihood of large increases in pH at the polymer/metal interface and so stabilizes the coating against cathodic disbondment. Further work is clearly needed to increase the protection period by further studies on the corrosion protection mechanism so that the polymer composition and processing methods may be optimized.     

Ultrafine grain formation and coating mechanism arising from a blast coating process: A transmission electron microscopy analysis

This article examines the substrate/coating interface of a coating deposited onto mild steel and stainless steel substrates using an ambient temperature blast coating technique known as CoBlast. The process uses a coincident stream of an abrasive blast medium and coating medium particles to modify the substrate surface. The hypothesis for the high bond strength is that the abrasive medium roughens the surface while simultaneously disrupting the passivating oxide layer of the substrate, thereby exposing the reactive metal that then reacts with the coating medium. The aim of this study is to provide greater insight into the coating/substrate bonding mechanism by analysing the interface between a hydroxyapatite coating on both mild and stainless steel substrates. The coating adhesion was measured via a tensile test, and bond strengths of approximately 45 MPa were measured. The substrate/coating interface was examined using transmission electron microscopy and selected area diffraction. The analysis of the substrate/coating interface revealed the presence of ultrafine grains in both the coating and substrate at interface associated with deformation at the interface caused by particle impaction during deposition. The chemical reactivity resulting from the creation of these ultrafine grains is proposed to explain the high adhesive strength of CoBlast coatings.     

Molecularly imprinted polymer coated solid-phase microextraction fibers for determination of Sudan I–IV dyes in hot chili powder and poultry feed samples

In this research, a novel strategy was developed to prepare molecularly imprinted polymer (MIP) coated solid-phase microextraction fibers on a large scale with Sudan I as template and stainless steel fibers as substrate. More than 20 fibers could be obtained in one glass tube, and the efficiency and coating repeatability were enhanced remarkably in contrast with the yield of only one fiber in our previous works. The obtained MIP-coated stainless steel fibers were characterized by homogeneous and highly cross-linked coating, good chemical and thermal stabilities, high extraction capacities, and specific selectivities to Sudan I–IV dyes. Based on the systemic optimization of extraction conditions, a simple and cost-effective method based on the coupling of MIP-coated SPME with high-performance liquid chromatography was developed for the fast and selective determination of trace Sudan I–IV dyes in hot chili powder and poultry feed samples. The limits of detection of Sudan I–IV dyes were within 2.5–4.6 ng g^?1, and the spiked recoveries were in the range of 86.3–96.3% for hot chili powder sample and 84.6–97.4% for poultry feed sample.     

Preparation of block copolymer of poly(trimethylene carbonate) with oligo(ethylene glycol) and the surface properties of the dip coated film

To persuade the stent coating materials for the better sustainable development, a block copolymer composed of hydrophobicity of poly(trimethylene carbonate) (PTMC) and hydrophilicity of PTMC bearing ethylene glycol chains was synthesized as a potential candidate. The result of thermal stability of the polymer was analyzed which reached up to 206 °C (T₁₀) and it is considered that sufficient for sterilization during the treatment. Moreover, the dip coated films of polymer were coated on polyethylene (PE) and stainless steel (SS) substrates in order to stimulate the stability upon the physiological environment. In addition, the preliminary in vitro test of the films were evaluated by protein adsorption and blood platelet adhesion tests. Hence, this study tends to convince that the synthetic block copolymer based on PTMC derivatives were approached for stent coating materials.     

石墨烯层层键合固相微萃取纤维的制备及对多环芳烃的检测

通过3-巯基丙基三甲氧基硅烷处理银层包裹的不锈钢纤维,得到Si-OH功能化的纤维,氧化石墨烯被层层键合到Si-OH功能化的纤维上,还原氧化石墨烯得到石墨烯层层键合的固相微萃取纤维。该方法制备的新型石墨烯层层键合的固相微萃取纤维具有制备简单,机械性能强,萃取涂层牢固,萃取能力强等优势。建立具有较宽线性范围(5~200μg/L)、较低检测限(0.007~0.09μg/L)的固相微萃取-气相色谱分析方法,用该方法测定河水和雨水中多环芳烃的含量。所制备的新型纤维重现性好、稳定性高、萃取能力强,可实现对多环芳烃的痕量检测。     

Improvement of interfacial adhesion of biodegradable polymers coated on metal surface by nanocoupling

A method of securing the adhesion of biodegradable polymer coating was investigated for drug-eluting metal stents, using surface-initiated ring-opening polymerization (SI-ROP) of L-lactide. Introduction of oligolactide on the stainless steel (SS) surface was successful and the thickness of the oligolactide grafts remained on the nanometer scale, as determined by ellipsometry. The presence of an oligolactide graft was also identified using attenuated total reflection-Fourier transform infrared (ATR-FTIR) and electron spectroscopy for chemical analysis (ESCA). On top of the grafts, poly(D,L-lactide-co-glycolide) (PLGA) coating was carried out on different substrates such as SS control, plasma-treated SS, and lactide-grafted (referred to as a nanocoupled) SS using electrospraying. When the adhesion forces were measured with a scratch tester, the nanocoupled SS showed the strongest interfacial adhesion between polymer coating layer and metal substrate. The outcome of the peel-off test was also consistent with the result of the scratch test. When degradation behavior of the polymer coating in vitro was examined for up to 4 weeks in a continuous fluid flow, the SEM images demonstrated that polymer degradation was obvious due to hydration and swelling of the polymer matrix. Although the matrix completely disappeared after 4 weeks for SS control and plasma-treated substrates, the nanocoupled SS was persistent with some polymer matrix. In addition, the release profiles of SRL-loaded PLGA coating appeared slightly different between control and nanocoupled groups. This work suggested that the concept of nanocoupling remarkably improved the interfacial adhesion stability between metal surface and polymer layer and controlled drug release, and showed the feasibility of drug-eluting stents.     

Corrosion and tribocorrosion behaviour of super‐thick diamond‐like carbon films deposited on stainless steel in NaCl solution

Super‐thick diamond‐like carbon (DLC) film is a potential protective coating in corrosive environments. In the present work, three kinds of DLC films whose thickness and modulation periods are 4 µm and 3, 21 µm and 17 and 21 µm and 7, respectively, were fabricated on stainless steel. The effect of different thickness and modulation periods on corrosion and tribocorrosion behaviour of the DLC‐coating stainless steel was investigated in 3.5 wt% NaCl aqueous solution by a ball‐on‐flat tribometer equipped with a three‐electrode electrochemical cell. The DLC‐coating stainless steel served as a working electrode, and its OCP and potentiodynamic polarization were monitored before and during rubbing. The wear–corrosion mechanism of the DLC films was investigated by SEM. The results showed that the increasing thickness can prolong significantly lifetime of DLC films in NaCl aqueous solution. In particular, the modulation period has a significant impact on the tribocorrosion resistance of the DLC super‐thick films. The study suggested that the increasing thickness of compressive stress layer could suppress film damage by reducing crack propagation rate. Thus, the super‐thick DLC film with thickness of 21 µm and 7 periods presented the best tribocorrosion resistance among all studied films. Copyright © 2016 John Wiley & Sons, Ltd.