Mechanism of adhesion promotion between aluminium sheet and polypropylene with maleic anhydride‐grafted polypropylene by γ‐aminopropyltriethoxy silane

The effect of concentration of γ‐aminopropyltriethoxy (γ‐APS) solution on shear strength of adhesive bonding between aluminium sheet and polypropylene (PP) with addition of a certain amount of maleic anhydride‐grafted polypropylene (PP‐g‐MAH) has been investigated. It is shown that the lap shear strength is promoted obviously with pre‐treatment of aluminium sheet by γ‐APS. The maximum strength is obtained at a concentration of 3% γ‐APS solution. With further high concentration of γ‐APS, the lap shear strength decreases. The examination of the separated surfaces by X‐ray photoelectron spectroscopy (XPS) shows that (C?O)₂? O? Al and C(?O)? O? Al are formed for adhesive bonding between PP with the addition of 20 wt% PP‐g‐MAH and aluminium sheet without pre‐treatment by γ‐APS, and that the area ratio of C related to oxygen on the separated aluminium side is 33.28%, which is obviously higher than 14% on the polymer side. As for adhesive bonding between PP with the addition of 20% PP‐g‐MAH and 3% γ‐APS pre‐treated aluminium sheet, C(?O)? N? C(?O) and C(?O)? NH are formed. The area ratio of C related to oxygen on the separated polymer side increases to 24.99%. It is proposed that γ‐APS pre‐treatment improves the distribution and shape of PP‐g‐MAH chains in the region adsorbed on the substrate and the region adjacent to this region. The chemical interactions at the interface are also proposed. Copyright © 2008 John Wiley & Sons, Ltd.     

Self-assembled molecular films of aminosilanes and their immobilization capacities

The assembly of two aminosilanes on silicon dioxide surfaces is investigated in this work. It is found that for 3-aminopropyltrimethoxysilane (APS), a smaller concentration of the silane and trace amounts of water in the deposition medium, an optimum time, and a postdeposition thermal curing are necessary to obtain a high primary-amine content. By optimization of deposition conditions, uniform APS films with a primary-amine content of 88.6% were obtained. The dependence of the primary-amine content on the experimental parameters is related to the extent to which amines are lost to hydrogen bonding with each other or with the substrate surface. Whenp-aminophenyltrimethoxysilane (APhS) was used, the primary-amine content in the film reached 100% and the surface morphology was more uniform than that of APS films under the same conditions. This is attributed to the rigid phenyl component in APhS that reduces opportunities for hydrogen bonding. In a comparison of the immobilization capacities of the different aminosilane substrates for pyromellitic dianhydride (PMDA), it is observed that higher primary-amine content favors higher uptake, and the APhS film yields 100% PMDA coverage. We infer that primary-amine content could be a measure of the film morphology and accessibility of the substrate amine groups.     

接触角法研究氨丙基硅烷化石英表面

利用接触角法研究了氨丙基硅烷化石英表面的基团浓度及单分子层中单个分子的截面积。提出了氨丙基硅烷化的模型。     

Facile preparation of stainless steel microextraction fiber via in situ growth of metal–organic framework UiO‐66 and its application to sensitive analysis of polycyclic musks

A functional stainless steel microextraction fiber easily prepared by in situ growing metal–organic framework UiO‐66 was presented and used for high‐performance analysis of polycyclic musks. Via the robust Ag‐SH bonding reaction, mercaptoacetic acid was easily anchored on Ag film to provide carboxyl group on the stainless steel fiber, then in situ grown UiO‐66 was fulfilled via the coordination reaction between Zr⁴⁺ and carboxyl group. Good characteristics including large surface area, high thermal stability, and good adsorption property were achieved. Sensitive detection limits (0.015–0.040 ng/L) were achieved for polycyclic musks by coupling with gas chromatography with mass spectrometry, and it could be stable enough for 150 extraction cycles without a significant loss of extraction efficiency. Compared with the classical commercial fibers, 2.2–11.4 times higher enhancement factors were shown. Applied to the analysis of fortified river water samples, five typical polycyclic musks were well detected with the recoveries of 90.2–101.8%, respectively. It showed a facile approach for preparing stainless steel microextraction fiber via chemically bonding in situ grown metal–organic framework for high‐performance enrichment.     

316L钢表面纳米银镀层的制备、性质及血液相容性

采用恒电位电沉积方法在316L不锈钢表面沉积银纳米镀层, 并将钢板置于全氟硅烷溶液中浸泡, 通过动态凝血实验、 抗凝血时间测定、 血小板黏附实验、 溶血实验和蛋白吸附实验等手段, 测试材料的血液相容性. 结果表明, 通过上述方法可明显改善316L不锈钢的血液相容性, 而抗凝血性能、 溶血率及纤维蛋白吸附量不亚于裸钢板. 与316L裸不锈钢相比, 银镀膜全氟硅烷浸泡316L不锈钢具有良好的血液相容性, 是一种比较理想的冠状动脉支架材料, 具有良好的应用前景.     

Construction and corrosion behaviors of a bilayer superhydrophobic film on copper substrate

A novel bilayer superhydrophobic film was constructed on Cu substrate by a simple multi‐step process. First, (3‐mercaptopropyl) trimethoxysilane (MPTMS) molecules were self‐assembled onto the pre‐etched Cu surface via covalent bonding followed by hydrolysis and condensation, then 1H, 1H, 2H, 2H‐perfluorodecyltrichlorosilane (PFDTS) were grafted onto the resultant hydroxyl terminated surface via the Si‐O‐Si bonding. The so‐prepared sample was defined as Cu‐MPTMS‐PFDTS. The structure and morphology of the samples were characterized by means of contact angle measurement, X‐ray photoelectron spectroscopy and scanning electron microscopy. The corrosion behaviors of the films were evaluated by Tafel plot and electrochemical impedance spectroscopy on an electrochemical work station. The results indicated that the bilayer superhydrophobic film possessed better corrosion protection as compared with the control samples. The superiority of the corrosion protection was mainly ascribed to the following two aspects: the superhydrophobicity and polysiloxane micro‐structures of the Cu‐MPTMS‐PFDTS. Copyright © 2012 John Wiley & Sons, Ltd.     

Pitting inhibition of stainless steel by surfactants: an electrochemical and surface chemical approach

Pitting corrosion of stainless steels causes tremendous damage in terms of material loss and resulting accidents. Organic surfactants have been tried as pitting inhibitors but the understanding of the inhibition mechanisms is mainly speculative. In the present study the inhibition of the pitting corrosion of 304 stainless steel by N-lauroylsarcosine sodium salt (NLS) in 0.1 M NaCl solutions at neutral pH was studied using an approach that combines surface chemical techniques with electrochemical ones. It was found that NLS increases the pitting resistance of 304 stainless steel, with possible complete inhibition at high NLS concentration (30 mM). Adsorption of NLS on 304 stainless steel particles was directly measured. NLS adsorbs significantly on 304 stainless steel with maximum adsorption density close to bilayer coverage. Electrophoretic mobility data for 304 stainless steel particles show that the surface of 304 stainless steel is negative in NaCl solution at neutral pH. The adsorption of NLS makes the interfacial charge even more negative. The relationship between pitting inhibition and adsorption density of NLS suggests that NLS does not adsorb preferentially on the pit nucleation sites and complete inhibition requires that the whole surface be covered completely by NLS. The inhibition mechanism of NLS is proposed to be due mainly to the blocking effect of a negatively charged NLS adsorption layer. This study shows that in addition to the adsorption amount of surfactant, interfacial charge also plays an important role in pitting inhibition.     

Interfacial chemistry of adhesives on hydrated aluminium and hydrated aluminium treated with an organosilane

The adsorption of a commercial adhesive and two of its major components—an amine curing agent [2,4‐toluene diisocyanate urone (TDI urone)] and an adhesive prepolymer resin [diglycidyl ether of bisphenol A (DGEBA)]—on a hydrated aluminium surface and the hydrated surface coated with γ‐glycidoxypropyltrimethoxysilane (GPS) has been investigated by x‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). The study of TDI urone adsorption indicated that adsorption was of the chemisorption type, and a specific interaction involving this molecule and the GPS immobilized on the hydrated aluminium surface was identified. From XPS and ToF‐SIMS data it was found that the types of interaction of the curing agent with the bare substrate were of the donor–acceptor type. Study of the DGEBA adsorption showed different‐shaped isotherms for the bare and the GPS‐coated substrates. It was found that the typical Langmuir isotherm type was obtained for the GPS‐coated substrate whereas no adsorption plateau was observed for the bare substrate within the concentration range studied. This resulted from a change in the conformation of the DGEBA molecule on the substrate when the concentration of DGEBA solution was increased. The bonding of DGEBA with both types of substrates was assumed to be via acid–base interactions (i.e. donor–acceptor interactions). Adsorption of the commercial adhesive on the hydrated surfaces was of BET Type IV form, rather than the simple monolayer adsorption isotherm (Langmuir type). This indicates multilayer adsorption, presumably in the pores of the hydrated substrate, as a result of a process analogous to adsorption condensation. Copyright © 2004 John Wiley & Sons, Ltd.     

Contribution of acidic amino residues to the adsorption of peptides onto a stainless steel surface

The role of the acidic amino acid residues in the adsorption of peptides/proteins onto stainless steel particles was investigated using a peptide fragment from bovine beta-lactoglobulin, Thr-Pro-Glu-Val-Asp-Asp-Glu-Ala-Leu-Glu-Lys (T5 peptide), which has a high affinity to a stainless steel surface at acidic pHs, and its mutant peptides substituted with different numbers of acidic amino acid residues. The adsorption behavior of the mutant peptides as well as the T5 peptide were studied at pH 3 with respect to concentration and ionic strength dependencies and the reversibility of the adsorption process. The behavior of the peptides was generally characterized as two distinct irreversible adsorption modes, Mode I and Mode II. In Mode I, the amounts adsorbed lay on the ordinate at zero equilibrium concentration in the solution, while in Mode II, the amount adsorbed increased with increased equilibrium concentration. The area occupied by the peptides was predicted by molecular mechanics and molecular dynamics. The state of the peptides, when adsorbed, was investigated using FT-IR analysis. The FT-IR analyses revealed that the side carboxylic groups of the peptides adsorbed on the stainless steel surface were ionized, while they were unionized in the solution at pH 3. Thus, the interactions between the carboxylic groups of the peptide and the stainless steel surface can be considered to be largely electrostatic. The peptide having four acidic amino acid residues took a maximum adsorbed amount, the reason for which is discussed.     

Reaction scheme of ammonia synthesis in the ECR plasmas

The reaction scheme of ammonia synthesis in the ECR plasma apparatus teas investigated from both identifications of the species in the plasmas and the adsorbed species on the surface of a steel substrate placed in the plasmas. The adsorbed species were considerably different when different kinds of plasmas are used. NH, species were adsorbed on the steel substrate surface in the nitrogen-hydrogen plasma, and N₂ molecules were adsorbed in the nitrogen plasma. By the application of a negative bias potential on the substrate, the adsorption of N atom or Fe-N bond formation was identified on the steel substrate surface. When the stainless steel wall of the chamber was covered with aluminum foil, the yield of NH,, radicals, which were on both the substrate and in the plasma, decreased. By exposure of the substrate, on which N₂ molecules or N atoms adsorbed, to the hydrogen plasma, N₂ and N disappeared from the steel substrate surface, forming ammonia. Moreover, the adsorption of NH,, radicals disappeared when the stainless steel wall surface was covered with aluminum foil. Thus, the surface of the stainless steel wall acts as a catalyst in ammonia formation. The formation of ammonia in the nitrogen-hydrogen ECR plasma, in which the steel substrate served as the catalyst, is not only through the dissociative adsorption of excited nitrogen molecules but also through the dissociative adsorption of nitrogen molecular ions.     

IR spectroscopy of N-methylpyrrole adsorbed on oxides--a probe of surface acidity

IR spectra of N-methylpyrrole (NMP) have been measured following adsorption on, and subsequent desorption from, SiO(2), TiO(2), ZrO(2), SiO(2)-Al(2)O(3), H-mordenite, and sepiolite. Three modes of adsorption have been observed: (i) hydrogen bonding to surface hydroxyl groups, (ii) electron transfer at Lewis acidic surface sites, and (iii) proton transfer at Br?nsted acidic surface sites. Protonation of NMP was detected only for adsorption on SiO(2)-Al(2)O(3) and H-mordenite, indicating the presence of Br?nsted acidic sites with pK(a) values 相似文献   

Adsorption of 2-chloropyridine on oxides--an infrared spectroscopic study

The adsorption of 2-chloropyridine on SiO(2), TiO(2), ZrO(2), SiO(2)-Al(2)O(3) and H-mordenite has been studied by IR spectroscopy. The different modes of interaction with oxide surfaces, i.e. hydrogen-bonding and adsorption at Br?nsted or Lewis acid sites, was modelled by ab initio calculations at the B3LYP/DZ+(d) level. Adsorption on SiO(2) results in hydrogen bonding to surface hydroxyl groups, whereas the spectra obtained following adsorption on TiO(2) and ZrO(2) display evidence for electron transfer at Lewis acidic surface sites. Protonation of 2-chloropyridine at Br?nsted acidic sites was detected only for adsorption on SiO(2)-Al(2)O(3) and H-mordenite, indicating the presence of Br?nsted acidic sites on these oxide surfaces with pK(a) values 相似文献   

Bovine serum albumin adsorption onto 316L stainless steel and alumina: a comparative study using depletion,protein radiolabeling,quartz crystal microbalance and atomic force microscopy

The importance of protein adsorption on biomaterials is widely recognized, but the dependence of the adsorption results on the chosen technique has not been much addressed. The objective of this work is to compare adsorption data obtained using several techniques under experimental conditions as closely as possible. Two case studies were investigated: adsorption of bovine serum albumin (BSA) onto 316L stainless steel (SS) and onto alumina. Both materials were used as powders and plates, whose characterization was done through zeta potential (ZP) measurements. The experimental techniques were depletion, protein radiolabeling, quartz crystal microbalance with dissipation (QCM‐D) and atomic force microscopy (AFM). The adsorption isotherms obtained with depletion and QCM‐D techniques, although quantitatively different, present some similarities in shape. Both techniques suggest the existence of a compact end‐on monolayer of protein on the SS surface, while on the alumina surface a less dense side‐on monolayer is formed at lower BSA concentration, followed by a second layer at higher concentration. AFM topographical characterization of the protein films adsorbed on both materials confirms those findings. Further use of AFM in determining the thickness of the film adsorbed on SS yielded values in good agreement with the QDM‐D results. Different surface charges measured on powders and plates do not seem to affect adsorption. Protein radiolabeling seems to be the least reliable technique because it yields, for both materials, adsorption values higher than those from the other techniques. In the case of SS, the difference amounts to one order of magnitude. Copyright © 2008 John Wiley & Sons, Ltd.     

Surface chemistry of ultrathin films of histidine on gold as probed by high-resolution synchrotron photoemission

Procedures for the vacuum deposition of thin histidine films on polycrystalline Au(111) and their characterization with high-resolution synchrotron-radiation-based photoelectron spectroscopy are reported. The chemical form of histidine (anionic vs zwitterionic) and the nature of its interactions with the substrate (strong ionic-covalent vs weak van der Waals bonding) in mono- and multilayer films are analyzed. It is shown that water adsorption on a pre-prepared histidine film at 100 K results in protonation of histidine molecules and partial formation of hydroxyl anions. These chemical effects are carefully differentiated from spectral changes associated with radiation damage of the histidine films.     

微纳米多孔不锈钢表面高效吸附活性生物大分子

不锈钢(AISI 316L)是目前在医药器械中应用最为广泛的商业化材料. 下一代的不锈钢智能材料将特殊功能的生物活性分子(或纳米粒子)修饰在金属表面以模拟组织功能、提高生物/细胞相容性, 这是目前材料科学研究的热点领域之一. 本文研究了具有微纳米多孔表面结构的316L 不锈钢对抗体和生物酶分子的吸附作用,并与这些生物分子在光滑表面以及镀金表面的吸附进行了比较. 研究发现不锈钢可通过简单的电化学腐蚀方法在表面产生微纳米多孔结构. 微纳米孔不锈钢表面可稳定地吸附抗体或辣根过氧化物酶分子, 其吸附量与喷镀金表面相当或更好. 用表面活性剂(10%牛血清白蛋白(BSA)或0.2% Tween-20)洗涤不能除去吸附的蛋白.用5% Tween-20 预处理金属表面, 则可减少一半的抗体吸附量; 但表面活性剂预处理对辣根过氧化物酶的吸附没有影响. 吸附蛋白质后的金属表面湿润度大大增加; 蛋白质修饰的微纳米孔不锈钢表面表现出了很好的亲水性(水接触角小于50°), 指示了很好的生物相容性. 而金属表面的湿润度则主要取决于蛋白质物种, 并与蛋白质的吸附量正相关. 吸附于不锈钢微纳米孔表面的抗体仍保持了良好的生物活性; 用此种方式制备的抗CD34抗体修饰的不锈钢血管支架可以高密度并高选择性地吸附其目标细胞(如KG-1细胞). 本文工作为未来制备新型的无高聚物涂层的不锈钢智能医学生物材料提供了基础.     

CO Adsorption on a LaNi5 Hydrogen Storage Alloy Surface: A Theoretical Investigation

Density functional theory calculations are carried out to study CO adsorption on the (001) surface of a LaNi₅ hydrogen storage alloy. At low coverages, CO favors adsorption on Ni? Ni bridge sites. With an increase in CO coverage, the decrease in the adsorption energy is much larger for Ni? Ni? CO bridge adsorption than that for Ni? CO on‐top adsorption. Thus, the latter sites in the relatively stable adsorption structure are preferentially utilized at high CO coverages. The nature of the bonding between CO and the LaNi₅ (001) surface is analyzed in detail.     

Interfacial Behavior of beta-Lactoglobulin at a Stainless Steel Surface: An Electrochemical Impedance Spectroscopy Study

The electrochemical impedance spectroscopy technique was used to investigate the interfacial behavior of beta-lactoglobulin at an austenitic stainless steel surface over the temperature range 299 to 343 K at an open circuit potential. The electrode/electrolyte interface and corresponding surface processes were successfully modeled by applying an equivalent-electrical-circuit approach. A charge-transfer resistance value was found to be very sensitive to the amount of adsorbed protein (surface concentration), thus indicating that the adsorption of the protein (i) was accompanied by the transfer of the charge, via chemisorption, and (ii) influenced the mechanism and kinetics of the corrosion reaction. This was also apparent from the large decrease in the corrosion activation energy (16 kJ mol(-1)) caused by the adsorption of the protein. Adsorption of beta-lactoglobulin onto the stainless steel surface at an open circuit potential resulted in a unimodal isotherm at all the temperatures studied and the adsorption process was described with a Langmuir adsorption isotherm. From the calculated Gibbs free energies of adsorption it was confirmed that beta-lactoglobulin molecules adsorb strongly onto the stainless steel surface. The enthalpy and entropy values indicated that the molecule partially unfolds at the surface upon adsorption. The adsorption process was found to be entirely governed by the change in entropy. Copyright 2000 Academic Press.     

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.     

Adsorption behavior of methylene blue and its congeners on a stainless steel surface

Methylene blue and its congeners as model dyes were adsorbed onto stainless steel particles at different ionic strengths, pH values, and ethanol contents, and the adsorption mechanism was investigated. A Fourier transform infrared spectroscopy (FTIR) analysis of the dyes adsorbed on the stainless steel plate was carried out to determine the orientations of the adsorbed dyes on stainless steel surface. The adsorption isotherms for all the dyes tested were approximated by a Langmuir equation (Q=Kq(m)C/(1+KC)) in most cases except under strongly basic conditions. From the ionic strength and ethanol content dependencies of the K value in the Langmuir equations, both the electrostatic and hydrophobic interactions were indicated to contribute to the adsorption of the dyes at neutral pH. By comparing the K and q(m) values for the methylene blue congeners and with the aid of the FTIR analyses, it was found that the kind of substituent groups at most positions of the polyheterocycles of methylene blue strongly affects the adsorption behavior, particularly the area occupied by an adsorbed dye molecule, the affinity for the stainless steel surface, and the orientation of the adsorbed dye molecule on the stainless steel surface.     

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.