Assembly behavior and monolayer characteristics of OH-terminated alkanethiol on Au(111): in situ scanning tunneling microscopy and electrochemical studies

Self-assembled monolayers (SAMs) of 6-mercapto-1-hexanol (MHO) on an Au(111) electrode were prepared in an electrochemical system. The adsorption behavior of MHO and the time-dependent organization of the SAM were investigated by in situ scanning tunneling microscopy (STM) and cyclic voltammetry (CV). The results show that a potential higher than 0.28?V (relative to RHE) is required to induce the adsorption of MHO. At 0.28?V, the MHO molecules adsorb in a flat-lying orientation, forming an ordered striped phase with a molecular arrangement of ([Formula: see text]). However, the adlayer is not stable at this potential. The adsorbed striped phase may recover to the herringbone feature of the gold substrate due to the desorption of adsorbed MHO. At a higher potential (0.35?V), the adlayer becomes stable and can undergo a phase evolution from the striped phase to a condensed structure, identified as c([Formula: see text]). This structure can also be described as a c(4 × 2) superlattice of a [Formula: see text] hexagonal adlattice. The surface coverage of the MHO SAM is identical to the saturated structure of an 11-mercapto-1-undecanol (MUO) SAM reported in a previous work, [Formula: see text]. However, the STM image of MHO adlayer shows a modulation in intensity, reflecting the presence of various conformations of adsorbed molecules. This result is attributed to the shorter chain length of MHO, which gives a weaker?van der Waals interaction between adsorbed molecules. This effect also results in a higher charge permeability across the adlayer and a lower striping potential to an MHO SAM.     

A pairwise interaction approach to the adsorption of oriented overgrowths

The adsorption energies and stable configurations of adlayers on different substrates of various orientations are calculated by means of a pairwise interaction model based on Lennard-Jones potentials. The adlayer is adsorbed onto a substrate consisting of a variable number of relaxed surface layers surmounting a much larger number of “rigid” layers fixed at bulk spacing. Special consideration is given to the adsorption of Cu, Ag and Pb on W and the adsorption of Ag on Cu.     

STM investigation of substitute effect on oligothiophene adlayer at Au(111) substrate

Molecular adlayers of a series of oligothiophenes with carboxylic groups and alkyl substitutes, DTDA, TTDA, QTDA, and PTDA, are investigated by STM at Au(111) surface. The effect of molecular structure including alkyl chain and thiophene backbone on the adlayer structure is revealed. DTDA and TTDA with two and three thiophene rings, self-assembled into highly ordered long-range two dimensional structures via hydrogen bondings, while QTDA with four thiophene rings formed short-range ordered structure with hexagonal symmetry. PTDA with five thiophene rings showed disordered pattern due to its strong molecule-substrate interaction. The results are compared with those on HOPG surface, showing that the molecule-substrate interaction plays an important role in the adlayer formation of these oligothiophenes.     

Potential-dependent adsorption and orientation of a small zwitterion: p-aminobenzoic acid on Ag(111)

We report on the potential-dependent behavior of the zwitterionic molecule p-aminobenzoic acid (PABA) at a Ag(111) electrode surface. Infrared-visible sum frequency generation spectroscopy (SFG) in tandem with electrochemical capacitance and CV measurements are used to study the effects of applied potential on the adsorption and orientation of PABA. Changes in the SFG signal indicate that PABA changes orientation in response to the charge on the electrode surface, orienting one way positive of the potential of zero charge (pzc) and oppositely negative of the pzc. At positive potentials, a phase change is observed associated with the formation of a condensed layer. PABA is observed to remain on the surface at all potentials examined. These results show that the orientation of small molecules with large dipoles, like zwitterions, can be controlled by applied potential.     

Determination of (111) ordered domains on platinum electrodes by irreversible adsorption of bismuth

Irreversible adsorbed bismuth can be used to determine the fraction of (111) domains on a given platinum sample. On Pt(111) electrodes, the surface redox process of adsorbed bismuth takes place at 0.63 V in a well-defined peak. The behavior of this redox process on the Pt(111) vicinal surfaces indicates that the bismuth atoms involved in the redox process are only those deposited on the (111) terrace sites and that the charge under the peak at 0.63 V is directly proportional to the number of sites on (111) ordered domains (terraces). The good linear relationship obtained between the charge for the bismuth redox process and the number of (111) terrace sites on the vicinal surfaces allows construction of a calibration curve. This calibration curve has been used to directly estimate the amount of (111) ordered domain terrace sites on polycrystalline platinum samples with different surface ordered domains. The results agree with what we would expect from our knowledge of these surfaces.     

噻二唑型缓蚀剂缓蚀性能的研究

利用电化学测试和表面分析技术,研究了2,5-二巯基-1,3,4噻二唑(DMTD)在硫-乙醇溶液中对金属银、铜的缓蚀性能,结合量子化学计算和分子动力学模拟对DMTD在金属表面的吸附行为和缓蚀作用机理进行了分析讨论。结果表明,DMTD在50mg/L的硫-乙醇溶液中,对金属银、铜均起到较好的缓蚀作用。极化曲线结果表明,当缓蚀剂DMTD浓度达到50mg/L时,缓蚀效率可以达到92.3%。表面分析技术表明,缓蚀剂的加入在金属表面形成吸附膜,明显抑制了腐蚀速率。量化计算和分子动力学模拟得到了缓蚀剂分子的活性位点和缓蚀剂在金属表面的吸附形态。     

Selective adsorption of organosilane molecules along step edges of atomically flattened Si(111) surfaces

We investigate the selective adsorption of organosilane molecules (3-aminopropyltriethoxysilane (APTES) and octadecyltrichlorosilane (OTS)) at the step edges of a flattened Si(111) surface by atomic force microscopy. The flattened Si(111) surface is formed by dipping a vicinal Si(111) wafer into ultralow-dissolved-oxygen water after treatment with HF. The selective adsorption of these organosilanes is achieved only when the Si(111) sample is pretreated with a Cu-containing solution to form Cu wires along the step edges of the Si(111) surface. This is probably due to the simultaneous formation of one-dimensional Si oxide covered with hydroxyl (OH) groups underneath Cu wires during the electroless reduction of Cu ions in water. At the step edges, APTES and OTS molecules are adsorbed as disperse clusters and as rows of bumps, respectively. The reason for this difference is still unclear, but a key factor is probably the control of the moisture content in the environment. The step edges, which are functionalized by organosilane molecules with various terminations such as -NH2 and -CH3, are expected to be utilized in novel nanoscale devices and processes.     

Comparative study of adatom manipulation on several fcc metal surfaces

For a set of fcc metals, our total energy calculations based on many body potentials show that activation barriers for lateral manipulation of an adatom at a step edge depend on the tip/substrate composition. Of the six homogeneous systems studied, manipulation on stepped Ag(111) showed the lowest energy barrier for adatom hopping toward the tip, although the relative probability for this process was largest on Cu(111). For a representative Cu/Pt heterogeneous system, we find lateral manipulation of a Pt adatom along a step on Pt(111) by a Cu(100) tip to be energetically much less favorable than the reverse case of a Cu adatom manipulated by a Pt(100) tip. In the case of vertical manipulation, atomic relaxations of the tip and its neighboring atoms are found to be prominent and tip-induced changes in the bonding of the adatom to its low coordinated surroundings help explain the relative ease with which an adatom next to a step edge or a kink site may be pulled as compared to that on a flat surface.     

复合气相缓蚀剂对纯铜缓蚀的研究

铜应用广泛,但在湿度较高的腐蚀性介质中其易被腐蚀,采用苯骈三氮唑(BTA)和酚类W制成一种新型复合气相缓蚀剂,采用原子分光光度计和电化学测试方法、扫描电镜和激光拉曼显微镜研究了该复合气相缓蚀剂对纯铜的缓蚀性能及其缓蚀机理.结果表明,该复合气相缓蚀剂在铜表面形成的膜是一种自组装缓蚀膜,具有很好的防蚀和拒水性能.     

Preliminary study of adsorption behavior of bovine serum albumin(BSA) protein and its effect on antibacterial and corrosion property of Ti-3Cu alloy

The adsorption behavior,antibacterial,and corrosion properties of a Ti-3Cu alloy were studied in a phosphate-buffered saline solution containing 0,1,3,and 6 g L-1 bovine serum albumin protein at 37 ℃and pH =7.4 (±0.2).The protein adsorption behavior was examined via cyclic voltammetry,secondary ions mass spectroscopy (SIMS),and angle-resolved X-ray photoelectron spectroscopy (ARXPS).The cor-rosion property was analyzed by the open circuit potential (OCP),potentiodynamic polarization (PD),and electrochemical impedance spectroscopy (EIS) examinations.The antibacterial test was conducted according to the GB/T 21510 China Standard.It was observed that the surface charge density (Q～s) was directly proportional to the amount of the adsorbed BSA protein,signifying that the protein adsorption was accompanied by the charge transfer,pointing to chemisorptions phenomena.BSA amino groups and other organic species were observed in the surface analysis examinations.It was shown that the formation of barrier complexes between the TiO2 oxide-layer and PBS solution resulted in decreasing the release of Cu-ions,which consequently reduced the antibacterial activity.On the other hand,these barrier complexes improved the corrosion resistance by increasing the charge transfer resistance and double-layer capacitance of the Ti-3Cu alloy.     

苯骈三氮唑酰基衍生物的缓蚀性能

合成了四种苯骈三氮唑（BTA）的酰基衍生物。并采用失重法、电化学法和表面分析法研究了它们在3％NaCl溶液中对铜的缓蚀作用。结果表明：BTA的四种酰基衍生物的缓蚀性能均优于BTA，X4－BTA由于与一阶铜离子形成螯合物而使其缓蚀性能显著增强。     

Corrosion behavior of bulk nanocrystalline copper in ammonia solution

Corrosion behavior of copper bulk with grain size of 48 nm prepared by inert gas condensation and in situ warm compress (IGCWC) technique was investigated in 0.3 wt.% ammonia solution. The nanocrystalline (NC) Cu sample displayed an active-passive-transpassive behavior with the formation of duplex passive films but without stable passive regions in potentiodynamic polarization process. NC Cu exhibited slightly inferior corrosion resistance when compared with coarse-grained (CG) Cu. It could be explained by both the higher grain boundary density that could accelerate corrosion reactions and the loose passive film formed on the surface of NC Cu that couldn't provide effective protection.     

Controllable electrodeposition of ordered carbon nanowalls on Cu(111) substrates

We report the growth of amorphous carbon nanowalls with molten salt electrolytes and a carbonate carbon source at 600 °C on home-made Cu(111) foil as the growth substrate (and cathode). The nanometer thick nanowalls grow preferentially along symmetric slip lines on the Cu(111) surface and their ordered arrangement appears to also be dictated by the electrosynthesis parameters. Computational chemistry suggests that nucleation of carbon growth is favored at the slip lines (atomic steps) of the Cu(111) surface. The electrodeposited carbon structures can be varied by tuning the potential on the electrodes and temperature of the molten salt. The macro, micro, and nanoscale structure of the nanowalls was studied and is reported.     

A mussel-inspired delivery system for enhancing self-healing property of epoxy coatings

Dopamine (DA),one type of mussel-inspired biological molecules with adhesive nature and corrosion inhibitor property,are often used to functionalize the surfaces of various materials.Herein,we report the application of polydopamine (PDA) microcapsules as novel nanocontainers for the purpose,loading corrosion inhibitor (benzotriazole) in its shell structure,and then were embedded into epoxy coatings to provide self-healing and anti-corrosion protection for carbon steel.Fast release of benzotriazole in acidic environment caused by local corrosion and the chelating effect of PDA-Fe3+ can synergistically promote the formation of protective film on bare steel surface,which endows coatings with self-healing func-tionality.Electrochemical impedance spectroscopy (EIS),local electrochemical impedance spectroscopy(LEIS),and spray tests were conducted to evaluate the active inhibition and corrosion resistance of the loaded coatings.The scratched coating with incorporation of nanocontainers presented better protection performance,exhibiting increased Ro (oxide layer resistance) and Rct (charge transfer resistance) during initial immersion periods.The EIS tests in long-term immersion were also performed to confirm the anti-corrosion effect of composited coatings.These results demonstrated that benzotriazole-decorated PDA capsules dramatically enhanced the self-healing properties and anti-corrosion performance of epoxy coatings with the synergistic help of PDA and benzotriazole.     

In Situ Scanning-Tunneling-Microscope Observation on Dissolution of a Cu-20Zr Film

A nanocrystalline coating of Cu-20Zr (in wt pct) was obtained on glass by magnetron sputtering. The corrosion behavior of the Cu-20Zr film in 0.001 mol/L HCI solution was investigated using potentiodynamic polarization and in situ electrochemical scanning-tunneling-microscopy (ECSTM). Results demonstrated that the film exhibits active behavior. Microscopic pitting corrosion and tunneling are caused by localized electrodissolution of Zr atoms and the diffusion of Cu atoms at surface defects.     

3D ES势垒对Cu(111)和Cu(OO1)晶面同质外延生长的影响

三维3D ES势垒直接影响着层间扩散,在Cu(111)和Cu(100)面2D ES势垒和3D ES势垒是不同的.本文主要研究了基于(1+1)维KMC模型,在这两个特殊的晶面上Cu薄膜的同质外延生长.观察两个面的生长情况,发现随着温度的增加薄膜的粗糙度逐渐减小,由于Cu(111)表面2D ES势垒较小,所以Cu(111)面粗糙度的下降的速度比Cu(100)要快,Cu(111)表面更有利于薄膜的生长.对于纳米棒的应用,在生长时间较短时两个面的生长速率逐渐减小,但是Cu(100)面的生长速度比Cu(111)面更快,随着生长时间的增加,这两个面会出现多层台阶,Cu(111)面的生长速度会逐渐增加,最终会超过了Cu(100)面.多层台阶出现后对两个面的影响是不同的.由于Cu(111)表面3D ES势垒较大,在Cu(111)表面会形成较多的多层台阶,Cu(111)面上多层台阶数有利于纳米棒的生长,然而在Cu(100)表面3D ES势垒较小,Cu(100)表面很难形成多层台阶,所以Cu(100)面上纳米棒的生长速度并没有增加.正是因为3D ES势垒的存在才会导致多层台阶的出现,较大的3D ES势垒有利于纳米棒的生长.     

溴化锂溶液中苯并三氮唑对碳钢缓蚀作用研究

为降低溴冷机中碳钢的腐蚀,通过失重法和电化学方法研究了含有0.07 mol/L LiOH和150mg/L Na2MoO4的55%LiBr、60%LiBr溶液中苯并三氮唑(BTA)对碳钢的缓蚀作用.结果表明,在溴化锂溶液中添加BTA时可显著降低碳钢腐蚀;55%LiBr、60%LiBr溶液中BTA的最佳添加量为100 mg/L;55%LiBr溶液中,BTA通过与铁离子形成Fe-BTA型配合物覆盖在金属表面阻碍浸蚀性Br-吸附而起缓蚀作用;60%LiBr溶液中,BTA则与MoO42-共同作用,在碳钢表面形成MoO2、MoO3和Fe-BTA致密钝化膜减缓金属活性溶解.     

微观组织对0Cr17Ni4Cu4Nb马氏体不锈钢的耐点腐蚀性能的影响

采用化学浸泡法和模拟闭塞电池方法研究了固溶+时效和固溶+调整+时效处理的0Cr17Ni4Cu4Nb马氏体不锈钢的耐点腐蚀性能,并与18-8型奥氏体不锈钢(316L)耐点蚀性能进行了对比。结果表明,0Cr17Ni4Cu4Nb马氏体不锈钢组织内富Cu析出相促进了点蚀坑萌生,而点蚀坑发展则与组织形貌有关。固溶+调整+时效处理的0Cr17Ni4Cu4Nb马氏体不锈钢因组织内析出富Cu相多而大,其萌生的点蚀坑密度较高,但由于马氏体板条较细,其点蚀坑尺寸和深度较小;固溶+时效处理的0Cr17Ni4Cu4Nb马氏体不锈钢因组织内析出富Cu相少而小,萌生的点蚀坑密度较低,但粗大的板条马氏体组织导致点蚀坑尺寸和深度较大。与18-8型奥氏体不锈钢耐点蚀性能对比表明,通过对0Cr17Ni4Cu4Nb马氏体不锈钢进行合理的热处理,其耐点蚀性能可与18-8型奥氏体不锈钢相当。     

Corrosion Behavior of High Energy–High Rate Consolidated Graphite/Copper Metal Matrix Composites in Chloride Media

The corrosion behavior of particulate reinforced graphite/copper (Gr_p/Cu) metal matrix composites (MMCs) was studied in 3.5 wt.% sodium chloride solution using electrochemical techniques, ionic solution analysis, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) techniques. The materials under investigation were high energy-high rate (HEHR) consolidated Gr_p/Cu metal matrix composites. HEHR processing employs a 10 MJ homopolar generator that supplies a 100 kA pulse to rapidly heat and solidify the composite powder compact. This short time at high temperature and the preferential heating and melting at the graphite-copper interface serve to encapsulate the graphite reinforcement, thus providing a highly densified composite product. Initially the open circuit potential corrosion behavior of 1.2, 5, 15, 25, and 40 volume percent Gr_pCu composites was studied in aerated and deaerated 3.5 wt.% NaCl solution using SEM and EDX. Subsequently, the environmental stability of these composites was studied using electrochemical techniques such as polarization resistance and potentiodynamic polarization. The severity of corrosive attack increased with increasing graphite content and in aerated solutions. In addition, solutions from these tests were analyzed to determine the relative amounts of copper and carbon present in the electrolyte after polarization tests. Microscopic analysis techniques were used to characterize the corrosion morphologies and the extensive localized corrosion occurring at the graphite-copper interface. The effectiveness of benzotriazole as a corrosion inhibitor for the copper MMCs was also studied.     

激光冲击对X70焊接接头慢拉伸电化学腐蚀的影响

为了改善X70管线钢焊接接头慢拉伸电化学腐蚀性能,用激光冲击波对X70管线钢焊接接头表面进行强化处理.采用慢应变速率拉伸法分析了X70管线钢焊接接头,在不同H2S浓度的NACE溶液(0.5%HAC+5%NaCl)中电化学腐蚀行为,测试了激光冲击处理前后X70管线钢焊接接头腐蚀电位,讨论了激光冲击处理对X70管线钢焊接接头腐蚀电位和断口形貌的影响.实验结果表明,激光冲击处理改善了X70管线钢焊接接头腐蚀性能,其SCC敏感性指数Iscc降低了6%.经激光冲击处理后试样自然腐蚀电位正移,极化电阻逐渐增大,其耐蚀性比原始状态有所提高.