Surface activation influencing the microstructure of Zn(Ca) phosphate coatings

Zinc and zinc calcium phosphate coatings on steel were formed by dipping in commercial baths. A surface activation with titanium phosphate influences not only the film morphology but also the composition of the conversion films. Qualitative phase analysis of the polycrystalline deposits reveals a typical phosphophyllite crystal growth apart from hopeite and scholzite respectively. The growth rate depends on the free surface of the steel; the contact area to the solution controls the rate of iron pickling.     

IR-Spectroscopic investigations on phosphated galvanized steel

Hopeite-type phosphate coatings in which zinc is replaced by other metals like nickel, manganese and magnesium are of great interest as conversion coatings on galvanized steel in the automotive and appliance industries. The analytical characterization of such coatings produced in special processes is not possible by XRD because the different types of hopeite are isomorphic. In this paper it is shown that the kind of metal substitution is responsible for certain specific features in the infrared reflection spectra. Furthermore the structural changes caused by dehydration due to heating of the coatings were studied and differences in the thermal stability of the different coatings thus could be observed.     

Effects of Hydroxylamine Sulfate and Sodium Nitrite on Microstructure and Friction Behavior of Zinc Phosphating Coating on High Carbon Steel

Hydroxylamine sulfate (HAS) and sodium nitrite are used as the accelerators for zinc phosphate coating on high carbon steel. Phase evolution of phosphate coating was investigated by X-ray diffraction. It is found that the phosphating coatings are mainly composed of hopeite Zn₃Fe(PO₄)₂·4H₂O and phosphophyllite Zn₂Fe(PO₄)₂·4H₂O. The microstructural changes of the phosphate coating, as a function of phosphating time, were evaluated by scanning electron microscopy. Four-ball friction experiments reveal that hydroxylamine sulfate instead of sodium nitrite can effectively reduce the friction coefficient of lubricated phosphating coating. Therefore, it may be expected that HAS will be widely used as a fast and ECO-friendly accelerator in phosphate industry.     

AES investigation of thermally sprayed Al2O3 coatings on steel

Summary The investigation of plasma sprayed steel/Al₂O₃ composites by means of Auger Electron Spectroscopy (AES) combined with depth profile analysis is described. Incomplete sprayed Al₂O₃ layers permit analysis of single sprayed particles and of surrounding uncovered steel substrate regions. More complete coatings are separated from the substrates, so that contact surfaces of substrates and Al₂O₃ layers can be analyzed. In order to determine the influence of preheating the substrates on the interface widths between steel substrate and Al₂O₃ coating and therefore on the adherence mechanism, both procedures are carried out for two preheating temperatures. It is shown that preheating hardly effects the interface widths beneath single sprayed particles but it causes laterally constant widths for complete layer fragments. Additionally, a comprehensive view about oxide layer thicknesses on the steel substrates before and after plasma spraying is offered.     

Electrophoretic Deposition of Hydroxyapatite Coatings on Metal Substrates: A Nanoparticulate Dual-Coating Approach

Hydroxyapatite coatings can be readily deposited on metal substrates by electrophoretic deposition. However, subsequent sintering is highly problematic owing to the fact that temperatures in excess of 1100°C are required for commercial hydroxyapatite powders to achieve high density. Such temperatures damage the metal and induce metal-catalysed decomposition of the hydroxyapatite. Furthermore, the firing shrinkage of the hydroxyapatite coating on a constraining metal substrate leads to severe cracking. The present study has overcome these problems using a novel approach: the use of aged nanoparticulate hydroxyapatite sols (lower sintering temperature) and a dual coating strategy that overcomes the cracking problem. Dual layers of uncalcined hydroxyapatite (HAp) powder were electrophoretically coated on Ti, Ti6Al4V and 316L stainless steel metal substrates, sintered at 875–1000°C, and characterised by SEM and XRD, and interfacial shear strength measurement. Dual coatings on stainless steel had an average high bond strength (about 23 MPa), and dual coatings on titanium and titanium alloy had moderate strengths (about 14 and 11 MPa, respectively), in comparison with the measured shear strength of bone (35 MPa). SEM and XRD demonstrated that the second layer blended seamlessly with the first and filled the cracks in the first. The superior result on stainless steel is attributed to a more appropriate thermal expansion match with hydroxyapatite, the thinner oxide layer, or a combination of these factors.     

Corrosion behavior in artificial seawater of thermal-sprayed WC-CoCr coatings on mild steel by electrochemical impedance spectroscopy

The corrosion behavior in artificial seawater of different as-sprayed ceramic-metallic (cermet) coatings applied on low-alloy steel was studied. Five conditions, associated to modifications of the composition of the powder or deposition parameters were evaluated. The degradation mechanisms were studied during extended immersion tests using conventional electrochemical measurement and electrochemical impedance spectroscopy. The extended immersion tests reveal that these as-thermal-sprayed coatings present a cathodic behavior compared with steel. During the first hours of immersion, the electrolyte infiltrates the defects of the coatings, which then result to the local degradation of the substrate accelerated by the galvanic coupling with the cermet coating. Optical observations and Raman analyses reveal the formation of calcium carbonates like aragonite on the cermet surface, very close to the appearance of local anodic sites. The cross-sectioned views reveal the infiltration of the corrosive solution, and the depth penetration of the degradation of steel substrate probably due to the acidification of the anodic sites.     

疏水型纳米TiO_2膜的制备、表征及耐蚀性能研究

以乙酰乙酸乙酯(EAcAc)作稳定剂和阻聚剂制备超微TiO2溶胶,用提拉法在AISI316L不锈钢上构筑一层纳米TiO2膜,经水热后处理有效消除膜中的龟裂现象,经氟硅烷基化制备成疏水型纳米TiO2膜.用胶粒分布仪测定溶胶颗粒分布,接触角测试仪测定表面疏水性、XRD、SEM表征膜的形貌、结构,电化学线性极化法测定疏水型纳米TiO2膜在模拟体液(Ringer溶液)中的电化学行为.结果表明:TiO2膜呈多孔有序纳米膜,颗粒分布均匀,粒径约为15～18nm,厚度约375nm,TiO2为锐钛矿型,疏水型纳米膜可使不锈钢腐蚀电流降低3个数量级,其耐腐蚀性大幅度提高.     

电化学法制备生物活性陶瓷材料研究

利用电化学方法可以在温和条件下制备生物活性陶瓷涂覆层，从而避免了高温喷涂引起的相变和脆裂，并可在形状复杂的基底上得到均匀的沉积层．因此，近年来在金属表面电沉积生物活性陶瓷涂覆层的研究方面已引起高度重视［’－‘j，然而，目前大多数文献报道所采用的恒电位方法，在沉积过程中电极表面的喊度会发生较大的变化，难以得到组分均匀的沉积层．本文报道用恒电流模式在Ti－6A14V合金表面沉积羟基磷灰石生物陶瓷涂层．1实验部分Ti－6A14V合金为电沉积基底（直径为0．65cm），辅助电极为Pt电极，参比电极采用饱和甘汞电极（SCE）．…     

Characterization of metallic layer composites by means of AES/depth profile analysis

The adherence mechanism of arc sprayed Ni layers on structure steel St37 is investigated. AES depth profiles are obtained on single Ni particles still adhering to the substrate after the Ni layer has been separated from it. A comparison of interface shapes and results of adherence measurements reveals Fe-Ni layered structures for the best adhering layers, whereas less adhering layers are characterized by narrower interfaces caused by diffusion. Areas with no adherence are covered with oxidic layers.     

电流密度对钙磷沉积层组成和结构的影响(英文)

用X射线衍射、激光拉曼光谱以及等离子体原子发射光谱等技术研究了电化学沉积钙磷陶瓷过程中 ,电流密度对电沉积层组成和结构的影响 .实验表明阴极表面得到的沉积物是几种钙磷盐组成的混合物 ,且其成份随电流密度的改变而发生较大的变化 .在电解液温度为 75℃条件下 ,当控制电流密度较低时 ,沉积层主要由CaHPO4· 2H2 O (DCPD)和Ca8H2 (PO4) 6· 5H2 O (OCP)组成 ;随着电流密度的增加 ,阴极表面逐渐生成Ca3 (PO4) 2 ·nH2 O (TCP)和Ca10 (PO4) 6(OH) 2 (HAP) .当电流密度大于 5mA/cm2 时 ,电沉积层的主要成份为羟基磷灰石 (HAP) .     

电沉积磷酸钙生物活性陶瓷

在医用合金Ti6A14V基底上研究了电流密度、阴极电位和电解液温度等实验条件对磷酸钙生物陶瓷电沉积层的组成、结构和表面形貌等特性的影响，用扫描电子显微镜（SEM）、X射线衍射（XRD）、傅立叶变换红外光谱（FTIR）和感耦等离子体原子发射光谱（ICP／AES）等技术对磷酸钙陶瓷沉积层进行了表征．依据各种用酸钙盐的热力学性质，采用低温城液后处理的方法将前驱体转化为均匀单一的多孔状纯羟基历灰石沉积层．     

Localization and chemical state of the third element (Zn,W) in electrolessly deposited nanocrystalline Ni-Zn-P,Ni-W-P and Co-W-P coatings

Electroless deposited Ni-P and Co-P coatings, modified by introducing additional elements such as Zn and W are presented. The characteristics alterations of the multicomponent films are reviewed in connection with the particularities of co-deposition of the third metal. Based on the fair correspondence between TEM, microdiffraction and precise XRD analysis it is shown that the structure type and lattice parameters of polycrystalline Ni-Me-P and Co-Me-P films are practically identical to pure Ni and Co metals. No impurity phase is detected by XRD. The location of the third element is determined using TEM with EDS. The conclusion is drawn about the grain boundary segregation of Zn and W along with P. Earlier studies by XPS and AES showed that Zn is partially oxidized, whereas W is in elemental form inside the coatings. Crystallites built of lamellas with thickness within the nanometer scale are observed in Ni-W-P and Co-W-P by TEM. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 6, pp. 764–770. The text was submitted by the authors in English.     

Characterization of nitrided and nitrocarburized surface compound layers of machine parts with AES

An investigation has been conducted into the contribution made by nitrogen and nitrogen plus carbon to the chemical composition of surface compound layers of non-alloy steel treated at 843 K. The composition of the compound layers produced by the optimized atmosphere systems was determined by AES. Recommendations are made on how such processes may be controlled.     

SiO2纳米粒子对溶胶凝胶涂层性能的影响

在高强钢表面制备了防护性溶胶凝胶涂层,并研究了不同浓度二氧化硅纳米粒子的加入对于涂层形貌、耐蚀性和硬度的影响。采用扫描电子显微镜(SEM)和电子能谱(EDS)观察了涂层的微观结构和成分;采用显微硬度计测试了涂层的硬度;采用电化学方法研究了二氧化硅纳米粒子的浓度对于涂层耐蚀性能的影响;采用傅里叶红外光谱研究涂层的化学结构,进而探讨了二氧化硅纳米粒子对于涂层的强化机理。结果显示涂层加入二氧化硅纳米粒子的最佳浓度为500 mg.L-1,此条件下的涂层表面均匀致密,有较高的硬度并且在3.5%NaCl溶液中体现出较好的耐蚀作用。纳米粒子在溶胶中反应形成活性羟基基团并与硅烷发生反应生成空间网状结构,从而强化涂层。     

Calibration of sputtering yields for AES depth profiling of oxide layers on aluminium by means of carrier-gas heat extraction analysis

Summary For the purpose of obtaining suitable reference materials for technical coatings on aluminium, the feasibility of calibration of oxide layers by means of heat extraction was studied. Oxide layers were prepared on aluminium sheets by immersion in water of 50 or 80 ° C and annealing at 500 or 600 °C in argon atmosphere. The layer thickness was calculated from the oxygen content of the sample as measured by carrier-gas heat extraction analysis.The total sputtering yield of aluminium oxide layers was obtained via the correlation of AES depth profiling with heat extraction analysis results. This was demonstrated for high purity (99.9%) and technical purity (98.5%) aluminium with its original roughness from the rolling process, on which 20 to 1,000 nm thick oxide layers had been grown.The sputtering yields for the oxide layers prepared were found to be 3.9±0.8 atoms/ion, i.e., about four times higher than that for -Al₂O₃. Calibration of depth profiling on such technical quality oxide layers on aluminium was found to be feasible with a relative precision of 10 to 20%.

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Kalibrierung der Ionenzerstäubung zur AES-Tiefenprofilanalyse von Oxidschichten auf Aluminium durch Trägergas-Heißextraktion

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On leave from the Institute of Photographic Chemistry, Academia Sinica, Beijing, People's Republic of China     

Electrochemical analysis of molybdate conversion coating on hot‐dip galvanized steel in various growth stages

The electrochemical behavior of molybdate conversion coatings in various growth stages was investigated by electrochemical impedance spectroscopy and equivalent circuits. The chemical composition and microstructure were characterized by SEM/energy dispersive spectroscopy, atomic force microscopy, and AES. Neutral salt spray tests complemented the information. The results indicated that the growth process of the molybdate conversion coating was accompanied by the growth of micro cracks, consisting of three stages: in the early and middle stages, the protective property of the coatings increased with increasing treatment time and then decreased when the cracks developed in the last stage. On the basis of the observation of the microstructure and the analysis of the electrochemical impedance spectra of the coatings in various stages, a simplified growth process model of the molybdate conversion coating on hot‐dip galvanized steel was created. Copyright © 2017 John Wiley & Sons, Ltd.     

Ultrathin coatings from isocyanate terminated star PEG prepolymers: patterning of proteins on the layers

This study presents the easy and fast patterning of low molecular weight molecules that act as binding partners for proteins on Star PEG coatings. These coatings are prepared from isocyanate terminated star shaped prepolymers and form a highly cross-linked network on the substrate in which the stars are connected via urea groups and free amino groups are present. Streptavidin has been patterned on these layers by microcontact printing (muCP) of an amino reactive biotin derivative and consecutive binding of streptavidin to the biotin. Patterns of Ni(2+)-nitriltriacetic acid (NTA) receptors have been prepared by printing amino functional NTA molecules in freshly prepared Star PEG layers that still contain amino reactive isocyanate groups. Complexation of the NTA groups with Ni(II) ions enabled the binding of His-tag enhanced green fluorescent protein (EGFP) in the desired pattern on the substrates. Since the unmodified Star PEG layers prevent unspecific protein adsorption, His-EGFP could selectively be bound to the sample by immersion into crude, nonpurified His-tag EGFP containing cell lysate.     

Ni-P-Zn_3(PO_4)_2(ZnSnO_3、ZnSiO_3)纳米复合化学镀层性质和组成的研究

研究了温度、时间、浓度等对 A3钢片上 Ni-P-Zn3(PO4)2、 Ni-P-ZnSnO3和 Ni-P-ZnSiO3纳米复合化学镀层外貌的影响。用扫描电子显微镜（ SEM）观察外貌;称重法测定厚度;通过 10％ NaCl溶液、 1％ H2S气体加速腐蚀试验、 10％ CuSO4溶液点滴试验等多种手段测定其耐腐蚀性能;用 X-射线光电子谱 (XPS)及俄歇电子能谱 (AES)测定其价态及组成。结果表明：在最佳施镀条件下,可得光亮、致密、耐腐蚀性强于 A3钢、磷化膜及 Ni-P镀层的纳米复合化学镀层。镀层的原子百分组成约为 (％ )： Ni-P-Zn3(PO4)2： Ni 70.00,P 12.47,Zn3(PO4)2 13.93,C 3.6; Ni-P-ZnSnO3： Ni 77.56,P 10.00,ZnSnO3 9.84,C 2.6; Ni-P-ZnSiO3： Ni 83.00,P 10.96,ZnSiO3 5.15,C 0.89。     

Application of the analytical methods REM/EDX, AES and SNMS to a chlorine induced aluminium corrosion

Summary Scanning electron microscopy (SEM) with energy dispersive X-ray detection (EDX), Auger electron spectroscopy (AES) and sputtered neutral mass spectrometry (SNMS) have been used to characterize a chlorine induced corrosion of an aluminium metallisation. SEM/EDX detects the characteristic X-rays, that are emitted from the first few micrometers beneath the specimens surface after inner shell ionisation by the primary electrons. AES detects the alternatively ejected Auger electrons, that are generated within the topmost atomic layers of the sample. To obtain elemental concentration depth profils, the surface layers are removed by ion sputtering. Whereas AES detects the composition of the remaining surface, SNMS measures sputtered fluxes and does not suffer from preferential sputtering. As demonstrated by the example of a chlorine induced aluminium corrosion, these analytical methods are complementary with respect to quantification, chemical information and information depth. Only by simultaneous use measuring artifacts are detectable and able to be excluded from interpretation.     

Structural Characterization by SIMS of Alumina Coatings on Stainless Steel

Al₂O₃ coatings were obtained by the alkoxide route and deposited on stainless steel using the dip coating technique. The starting precursor was aluminum sec-butoxide modified by acrylic acid in order to prevent its precipitation in the presence of water.Useful information for the structural organization of alumina coatings on stainless steel is deduced from SIMS analysis. SIMS data reveal that the coating structure brings into play two different layers: an outer alumina layer that is more or less doped, mainly by iron, and an internal layer corresponding to the alumina/steel interphase. Beneath the interphase, the presence of an oxidized steel layer on the substrate surface is detected.Whatever the coating, the alumina/steel interphase exhibits a nearly constant thickness. On the other hand, a thickness variation of the oxidized steel layer is observed between samples under study: this thickness increases with the curing time of the coating.