The study of ceramic-like oxide coatings on zirconium produced by plasma treatment in electrolytes

Ceramic-like oxide coatings on zirconium with a thickness of up to 300 μm produced by plasma treatment in an electrolyte demonstrate high thermal resistivity and low thermal conductivity during high-temperature testing in a plasmatron in a plasma flow. Data on the structure of coatings and its changes during thermal testing obtained using the methods of scanning electron microscopy, X-ray diffraction analysis, and nuclear backscattering spectrometry are discussed.     

Investigation of zirconia coatings obtained under plasma action in electrolytes

The results of experiments on the production of zirconia (ZrO₂)-based thermal barriert coatings on copper substrates under plasma action in electrolytes on preliminary applied zirconium layers are represented. Structural-morphological investigations by scanning electron microscopy, X-ray analysis, and nuclear backscattering spectrometry showed that micro-arc oxidation (MAO) makes it possible to produce Zr-ZrO₂ coatings with a thermal barrier ZrO₂ layer with a thickness of more than 100 μm, which is separated from the substrate of the base by a dense MAO barrier layer and a nonoxidized zirconium layer.     

Influence of the bilayer thickness of nanostructured multilayer MoN/CrN coating on its microstructure,hardness, and elemental composition

Multilayer nanostructured coatings consisting of alternating MoN and CrN layers were obtained by vacuum cathode evaporation under various conditions of deposition. The transition from micron sizes of bilayers to the nanometer scale in the coatings under investigation leads to an increase in hardness from 15 to 35.5 GPa (with a layer thickness of about 35 nm). At the same time, when the number of bilayers in the coating decreases, the average Vickers hardness increases from 1267 HV_0.05 to 3307 HV_0.05. An increase in the value of the potential supplied to the substrate from–20 to–150 V leads to the formation of growth textures in coating layers with the [100] axis, and to an increase in the intensity of reflections with increasing bilayer thickness. Elemental analysis carried out with the help of Rutherford backscattering, secondary ion mass spectrometry and energy dispersion spectra showed a good separation of the MoN and CrN layers near the surface of the coatings.     

Investigation of Ceramic-Like Coatings Formed on Aluminum Composites by Microarc Oxidation

Ceramic-like coatings with a thickness of up to 40 μm are formed on aluminum composites without additives and with copper additives (1 and 4.5%) in a silicate-alkaline electrolyte by microarc oxidation. The composites are prepared by powder metallurgy (cold pressing and sintering in forevacuum). An increase in the copper concentration in the composites to 4.5% leads to the retardation of anode voltage growth on the initial stage of oxidation corresponding to the formation of a barrier layer. The coatings are studied by scanning electron microscopy, X-ray microanalysis, X-ray photoelectron spectroscopy, and X-ray diffraction. The morphology of their surface corresponds to the morphology of the surface of coatings on compact aluminum alloys. According to X-ray photoelectron spectroscopy, a thin 1-μm layer forms on the surface. It consists predominantly of electrolyte components. X-ray diffraction analysis shows that the coatings mainly consist of γ-Al₂O₃ oxide as well as the η-Al₂O₃ phase, the peaks of which are broadened. This broadening is characteristic of the amorphous component and may be due to the presence of nanocrystalline regions in the coating structure. In the coatings on the composite Al + 4.5% Cu, mullite Al₂SiO₅ and copper oxide CuO are also found. The excess aluminum content may be associated with residual unoxidized aluminum inclusions in the structure of the coatings.     

Properties and structure of oxidized coatings deposited onto Al-Cu and Al-Mg alloys

The results of new studies of creating protective oxide coatings based on Al₂O₃ (Si, Mn) and deposited onto aluminum alloys using electrolyte-plasma oxidation are presented. An analysis is performed by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), X-ray diffraction, Rutherford backscattering of ⁴He⁺ and protons, nanoindentation, scratching, friction coefficient measurements, and acoustic emission measurements. The results demonstrate that the deposited coatings have a high quality, hardness, and wear resistance and a low thermal diffusivity. Apart from Al₂O₃, the coatings are found to have Si, Mn, C, and Ca. The stoichiometry of the coatings is determined. The density and hardness of the coatings are close to those of ??-Al₂O₃ in the coating on an Al-Cu (D-16) substrate, and these values of the coating on an Al-Mg (S006) are lower by a factor of 1.5.     

Holographic diffraction gratings with multilayer insulator coatings

Based on numerical modeling of metallized diffraction gratings with multilayer insulator coatings, the diffraction efficiency of such gratings is investigated, assuming that the initial profile of the metallized grat-ing is not reproduced in the course of sequential deposition of coating layers. From comparison of experimental and calculated data, it is concluded that the initial grating relief is subject to considerable smoothing. The new nontraditional range of the optimum values of layer thicknesses, which provides a high diffraction efficiency in the operating wavelength range of 1.06 μm, is suggested. The stability of the diffraction efficiency with respect to random errors in the thickness of insulator layers deposited is investigated numerically.     

Microstructure and composition of catalytic layers formed by the ion-beam-assisted deposition of platinum onto carbon substrates

The results of investigating the microstructure and composition of layers formed by platinum deposition onto carbon carriers used as electrocatalysts—MG-1 graphite, SU-2000 glassy carbon, and AVCarb® P50 carbon fiber paper—are presented. The layers have been created via the ion-beam-assisted deposition of platinum, in which metal deposition and mixing between the deposited layer and substrate-surface atoms accelerated by ions of the same metal (U = 10 kV) occur, respectively, from a neutral vapor fraction and the vacuum-arc discharge plasma of a pulsed ion source. The layers are examined via scanning electron microscopy, electron probe microanalysis, electron backscatter diffraction, Rutherford backscattering spectrometry, and X-ray photoelectron spectrometry. The formed layers (their thicknesses are ～100 nm and the platinum content is ～10¹⁶ atom cm^?2) are characterized by an amorphous atomic structure that repeats the surface microstructure of the carbon carrier.     

Auger electron spectroscopy depth profiling of Fe-oxide layers on electromagnetic sheets prepared by low temperature oxidation

Auger electron spectroscopy depth profiling was applied to characterize the Fe-oxide layers prepared by low temperature oxidation of Fe electromagnetic sheets produced on an industrial line for applications in the field of electrical motors. In addition the surface morphology, layer composition and layer structure were analysed by electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction techniques. We found that the oxide layers on Fe-sheets with good adhesion between the oxide layer and Fe-substrate, consist mainly of magnetite and to a smaller extent of haematite; the layers are typically thinner than 1 μm and the interface between the oxide layer and the Fe-substrate is relatively broad, i.e. up to 0.3 μm. On the contrary, a decrease of adhesion between the oxide layer and the Fe-substrate was found when the layer is thicker than 1 μm and the layer/substrate interface is narrow and contaminated by foreign elements.     

Analysis of the interface between a pulsed laser deposited calcium phosphate coating and a titanium alloy substrate

Calcium phosphate coatings deposited on titanium alloy are intended to add a bioactive surface to medical implants. This work presents the characterisation of the interface between Ti-6Al-4V and a crystalline calcium phosphate coating obtained by pulsed laser deposition, with a KrF excimer laser, at 575 °C and under a 45 Pa water-vapour atmosphere. The coating–substrate system was studied by secondary-ion mass spectrometry, scanning electron microscopy, X-ray diffractometry, Raman spectroscopy and X-ray photoelectron spectroscopy. The results show that the deposition process promotes the interdiffusion of substrate elements into the coating and coating elements into the substrate oxide layer. Thus, a graded layer of mixed calcium phosphate and amorphous titanium oxide is formed. For the substrate, a hydroxyapatite coating acts more as a barrier for oxygen incoming from a gas than as an oxygen source during deposition. Moreover, oxygen diffusion into the substrate occurs. Thus, the content of oxygen of this oxide layer diminishes with depth. When the oxygen concentration is low enough it is incorporated in solid solution in the titanium alloy . PACS 81.15.Fg; 68.55.-a; 87.68.+z     

Physical and mechanical properties of silicon near the SiO2/Si interface

The influence of an oxide coating on the strength characteristics of single-crystal silicon surface layers is investigated by the microindentation method. It is shown experimentally that a strengthened layer with a thickness of 0.2–0.4 μm and a microhardness of 20–35 GPa, which is two or three times as much as the microhardness of bulk single-crystal silicon, is present near the SiO₂/Si interface. The thickness and microhardness of this layer depends on the growth conditions of the oxide. The formation of this layer is most probably caused by interstitial silicon atoms formed near the SiO₂/Si interface during silicon oxidation.     

Multi-spectral antireflection coating on zinc sulphide simultaneously effective in visible,eye safe laser wave length and MWIR region

In recent years multi-spectral device is steadily growing popularity. Multi-spectral antireflection coating effective in visible region for sighting system, laser wavelength for ranging and MWIR region for thermal system can use common objective/receiver optics highly useful for state of art thermal instrumentation. In this paper, design and fabrication of antireflection coating simultaneously effective in visible region (450–650 nm), Eye safe laser wave length (1540 nm) and MWIR region (3.6–4.9 μm) has been reported. Comprehensive search method of design was used and the number of layers in the design was optimised with lowest evaluated merit function studied with respect to various layers. Finally eight-layer design stack was established using hafnium oxide as high index layer and silicon-di-oxide as low index coating material combination. The multilayer stack had been fabricated by using electron beam gun evaporation system in Symphony 9 vacuum coating unit. During layer deposition the substrate was irradiated with End-Hall ion gun. The evaporation was carried out in presence of oxygen and layer thicknesses were measured with crystal monitor. The result achieved for the antireflection coating was 85% average transmission from 450 to 650 nm in visible region, 95% transmission at 1540 nm and 96% average transmission from 3.6 to 4.9 μm in MWIR region.     

Microstructure characteristic of ceramic coatings fabricated on magnesium alloys by micro-arc oxidation in alkaline silicate solutions

Micro-arc oxidation (MAO) of AZ31B magnesium alloys was studied in alkaline silicate solutions at constant applied current densities. The microstructure, phase composition and elemental distribution of ceramic coatings were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDX). There are two inflections in the voltage-time response, three regions were identifiable and each of the regions was almost linear. The pores with different shapes distributed all over the coating surface, the number of the pores was decreasing, while the diameter was apparently increasing with prolonged MAO treatment time. There were also cracks on the coating surface, resulting from the rapid solidification of the molten oxide. The ceramic coating was comprised of two layers, an outer loose layer and an inner dense layer. The ceramic coating was mainly composed of forsterite phase Mg₂SiO₄ and MgO; the formation of MgO was similar to conversional anodizing technology, while formation of Mg₂SiO₄ was attributed to a high temperature phase transformation reaction. Presence of Si and O indicated that the electrolyte components had intensively incorporated into coatings.     

Examination of medicinal agents by nuclear backscattering spectrometry of protons

It is proposed to exam pelleted medicinal agents by nuclear backscattering spectrometry of protons. The backscattering spectra of 7.8-MeV protons have been measured for such medicinal agents as analginum, aspirin, lizobact, and berlicort, as well as for chalk and starch—examples of a base for forged medicinal agents. The measurement results indicate that proton backscattering spectrometry can be used to detect forged medicinal agents.     

Analysis of the composition of Ti-based thin films deposited on silicon by means of self-ion assisted deposition

The composition of Ti-based thin films deposited on silicon using a self-ion assisted deposition (SIAD) method was investigated by utilising the Rutherford backscattering spectrometry technique and RUMP simulation code. The hydrogen affinity of the coatings produced by means of SIAD was investigated using the ¹H(¹⁵N, αγ)¹²C nuclear resonance reaction. The titanium–based films on silicon were found to have a high content of oxygen, carbon, hydrogen and substantial concentration of the substrate. Near 10% H content enrichment was found at the surface of coatings but no hydrogen enrichment at the coating–substrate interfaces was observed.     

The role of goethite in the formation of the protective corrosion layer on steels

The corrosion products formed on carbon and weathering steels exposed in marine, industrial and rural environments in the United States for 16 years have been investigated using M?ssbauer spectroscopy, Raman spectrometry and chemical analysis. M?ssbauer spectroscopy was used to measure the fraction of each oxide in the corrosion coatings and micro-Raman spectrometry was used to locate and map the oxides to 2 μm spatial resolution. M?ssbauer spectroscopy identified the corrosion products in the weathering steels as 75% goethite, 20% lepidocrocite and 5% maghemite. Raman analysis showed that the corrosion products generally formed as alternating layers containing different oxides. For the weathering steels the protective inner-layer closest to the steel substrate consisted of nano-sized goethite ranging in size from 5–30 nm and having a mean particle size of about 12 nm. The outer-layer close to the coating surface, consisted of lepidocrocite and goethite with the former oxide being most abundant. Electron probe micro-analysis measured significant chromium in the goethite close to the steel substrate. Comparison of the goethite in the corrosion products was made with synthetic chromium substituted goethite with nearly identical microstructural characteristics being recorded. It is concluded that chromium inclusions in the goethite are important for formation of a nano-phase oxide layer which may help protect the weathering steel from further corrosion. This revised version was published online in July 2006 with corrections to the Cover Date.     

Changes in the structural phase state of a copper substrate’s surface layer bombarded with titanium ions

The structural-phase state of a copper substrate’s surface layer treated with titanium ions is investigated. It is established via X-ray diffraction analysis that intermetalides of the Cu-Ti type formed in the surface layer following treatment. It is found by means of scanning electron microscopy that a netlike porous structure with characteristic crosswise horizontal and vertical element dimensions of ～1–2 μm forms in the surface layer.     

Diamond deposition on siliconized stainless steel

Silicon diffusion layers in AISI 304 and AISI 316 type stainless steels were investigated as an alternative to surface barrier coatings for diamond film growth. Uniform 2 μm thick silicon rich interlayers were obtained by coating the surface of the steels with silicon and performing diffusion treatments at 800 °C. Adherent diamond films with low sp² carbon content were deposited on the diffused silicon layers by a modified hot filament assisted chemical vapor deposition (HFCVD) method. Characterization of as-siliconized layers and diamond coatings was performed by energy dispersive X-ray analysis, scanning electron microscopy, X-ray diffraction and Raman spectroscopy.     

RB-SiC表面改性Si涂层的制备与性能

 为了获得高质量光学表面的碳化硅反射镜,利用射频磁控溅射方法,在直径70 mm的RB-SiC基片上沉积了厚约100 μm的Si改性涂层,对改性层进行超光滑加工,并对改性层的表面形貌及性能进行了测试。ZYGO表面粗糙度仪测试结果表明,抛光后Si改性涂层表面粗糙度均方根值达到了0.496 nm;X射线衍射仪测试显示,制备Si改性涂层为多晶结构;使用拉力机做附着力测试,结果表明膜基附着力大于10.7 MPa。证明采用磁控溅射技术制备的Si改性涂层均匀、致密、附着力好,能够满足RB-SiC材料表面改性要求。     

Characterization and oxidation behavior of NiCoCrAlY coating fabricated by electrophoretic deposition and vacuum heat treatment

Electrophoretic deposition (EPD) was showed to be a feasible and convenient method to fabricate NiCoCrAlY coatings on nickel based supperalloys. The microstructure and composition of the NiCoCrAlY coatings after vacuum heat treatment were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDAX). Isothermal-oxidation test was performed at 1100 °C in static air for 100 h. The results show that the major phases in electrophoretic deposited and vacuum heat treated NiCoCrAlY coating are γ-Ni and γ′-Ni₃Al phases, also there is an extremely small quantity of Al₂O₃ in the coating. Composition fluctuations occur in the coating and a certain amount of titanium diffuse from the superalloy substrate to the top of the coating during vacuum heat treatment. The oxidation test results exhibit that the oxidation kinetics of this coating has two typical stages. The protective oxide layer is mainly formed in the initial linear growth stage and then the oxide layer hinders further oxidation of the coating in the subsequent parabolic growth stage. The coating can effectively protect the superalloy substrate from oxidation. A certain amount of rutile TiO₂ is formed in the coating during oxidation and it is adverse to the oxidation resistance of the coating.     

Corrosion behavior and protective ability of Zn and Zn-Co electrodeposits with embedded polymeric nanoparticles

The anodic behavior, corrosion resistance and protective ability of Zn and alloyed Zn-Co (∼3 wt.%) nanocomposite coatings were investigated in a model corrosion medium of 5% NaCl solution. The metallic matrix of the layers incorporates core-shell nano-sized stabilized polymeric micelles (SPMs) obtained from poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) block co-polymers. The protective properties of the composite coatings were evaluated using potentiodynamic polarization technique, polarization resistance measurements and powder X-ray diffraction. The sizes and distribution of the stabilized polymeric micelles in the starting electrolytes used as well as in the metal matrices of the layers were investigated using scanning and transmission electron microscopy. The results obtained are compared to those of electrodeposited Zn and Zn-Co (∼3 wt.%) alloy coatings at identical conditions and demonstrate the enhanced protective characteristics of the Zn nanocomposites during the investigating period. The influence of the SPMs on the corrosion resistance of the nanocomposite layers is commented and discussed.