Pretreatment Of Substrate Surface Research Articles

Erosion Resistance of Valve Core Surface Combined with WC-10Co-4Cr Coating Process under Different Pretreatments.

The erosion of the valve core causes valve failure problems. Thus, a novel method to extend the erosion resistance of the valve was innovatively proposed, namely, nanosecond laser ablation micro-pits on the substrate surface and high velocity oxygen fuel (HVOF) spraying WC coating to extend the erosion resistance of the valve. The characterization and evaluation of the erosion resistance of the WC-sprayed coating after the pretreatment of the 3Cr13 substrate surface polishing/grit blasting/nanosecond laser ablation circular micro-dimple were conducted using the unit coupon erosion test of liquid-solid two-phase flow, followed by the test evaluation and analysis of the erosion resistance test of the WC coating after different pretreatments of the full-size valve core. Results showed that the micro-dimple pretreatment on the surface of the 3Cr13 substrate increased the contact area rate and bonding strength of the substrate and the WC coating. By taking erosion volume loss as the evaluation index, the erosion resistance of the micro-dimple pretreatment on the surface of the 3Cr13 substrate was increased by about 31.98% compared with that of the polishing pretreatment. Therefore, the new method of surface nanosecond laser texture pretreatment and HVOF-spraying WC coating can effectively improve the erosion resistance of the valve.

Glass poling as a substrate surface pre-treatment for in situ metal nanoparticle formation by reduction of metal salt

Metal nanoparticles are used in optical coatings and sensors due to their absorption in optical part of spectrum and its sensitivity to the environment induced by localized surface plasmon resonance. Glass is the most common substrate used for optical coatings. However, its surface does not have optimal properties for coating with metal nanoparticles grown in situ by reduction of metal salt. Glass surface optimization methods may involve environmentally hostile chemicals or processes that have time limited or atmosphere sensitive effects. In this study it is demonstrated and discussed effectiveness, mechanisms and advantages of glass poling as pre-treatment method for improving glass surface properties for maximization of coatings plasmonic performance. Pre-treatment of glass surfaces by poling is highly efficient for the purpose. Glass poling quenches ion exchange between metal ions from the solution and alkali ions from glass, favouring nanoparticles formation. Surface prepared in such way is not affected by ageing in normal atmosphere and is effective even after coating with ultrathin dielectric or Cr layers.

Effect of Surface Pre-Treatment on Adhesive Strength of Multi-Component Vacuum-Arc Coatings

The results of investigations of multi-component nanostructured coatings of (TiAlSiY)N/CrN type are presented. The influence of different variants of substrate surface pretreatment on adhesive strength and hardness of coatings was studied. Pre-treatment of samples was carried out in plasma of two-stage gas discharge according to various technological schemes. Except for ion-plasma purification, some samples were pretreated with a sublayer of chromium within 5 minutes. The coatings were formed by a vacuum-arc deposition method at simultaneous spraying of two cathode targets. The first cathode is made of chromium, and the second cathode is made of multicomponent Ti - Al - Si - Y alloy obtained by vacuum-arc remelting of powder mixture of the mentioned elements. The coatings were deposited on polished stainless-steel substrates at negative 280 V bias potential. The geometry of the unit and its elements, as well as technological characteristics of the processes of evaporation-condensation were selected so that at a speed of rotation of samples 8 revolutions per minute the formation of the coating with a total thickness of about 9.0 microns occurred in approximately 60 minutes. The analysis of the composition of the coatings shows that the content of elements in the coating differs greatly from the content of elements in the sprayed cathodes. The X-ray diffractometry has shown that all deposition modes are characterized by the formation of phases with cubic (fcc) crystal lattice in both phase layers of multilayer coatings. In the layers formed at spraying of TiAlSiY alloy, a multi-element disordered solid solution (TiAlSiY)N with a crystal lattice of NaCl type and a lattice parameter of 0.4241 nm, as well as chromium mononitride CrN with a lattice parameter of 0.4161 nm, is determined. It has been established that preliminary formation of a chromium sublayer on the substrate leads to significant changes in adhesive strength of multi-component coatings compared to coatings without a sublayer.

Cellulose Nano-Films as Bio-Interfaces.

Cellulose, the most abundant polymer on earth, has enormous potential in developing bio-friendly, and sustainable technological products. In particular, cellulose films of nanoscale thickness (1–100 nm) are transparent, smooth (roughness <1 nm), and provide a large surface area interface for biomolecules immobilization and interactions. These attractive film properties create many possibilities for both fundamental studies and applications, especially in the biomedical field. The three liable—OH groups on the monomeric unit of the cellulose chain provide schemes to chemically modify the cellulose interface and engineer its properties. Here, the cellulose thin film serves as a substrate for biomolecules interactions and acts as a support for bio-diagnostics. This review focuses on the challenges and opportunities provided by engineering cellulose thin films for controlling biomolecules interactions. The first part reviews the methods for preparing cellulose thin films. These are by dispersing or dissolving pure cellulose or cellulose derivatives in a solvent to coat a substrate using the spin coating, Langmuir-Blodgett, or Langmuir-Schaefer method. It is shown how different cellulose sources, preparation, and coating methods and substrate surface pre-treatment affect the film thickness, roughness, morphology, crystallinity, swelling in water, and homogeneity. The second part analyses the bio-macromolecules interactions with the cellulose thin film interfaces. Biomolecules, such as antibodies and enzymes, are adsorbed at the cellulose-liquid interface, and analyzed dry and wet. This highlights the effect of film surface morphology, thickness, crystallinity, water intake capacity, and surface pre-treatment on biomolecule adsorption, conformation, coverage, longevity, and activity. Advance characterization of cellulose thin film interface morphology and adsorbed biomolecules interactions are next reviewed. X-ray and neutron scattering/reflectivity combined with atomic force microscopy (AFM), quartz crystal microbalance (QCM), microscopy, and ellipsometer allow visualizing, and quantifying the structural morphology of cellulose-biomolecule interphase and the respective biomolecules conformations, kinetics, and sorption mechanisms. This review provides a novel insight on the advantages and challenges of engineering cellulose thin films for biomedical applications. This is to foster the exploration at the molecular level of the interaction mechanisms between a cellulose interface and adsorbed biomolecules with respect to adsorbed molecules morphology, surface coverage, and quantity. This knowledge is to engineer a novel generation of efficient and functional biomedical devices.

Ti1−xAlxN coatings by Reactive High Power Impulse Magnetron Sputtering: film/substrate interface effect on residual stress and high temperature oxidation

To withstand oxidation at a temperature ≥ 850 °C, an optimized Ti1−xAlxN coating was grown via reactive High Power Impulse Magnetron Sputtering (HiPIMS) technology on three identical Ti0.48Al0.48Cr0.02Nb0.02 billets. Different substrate surface pre-treatments were designed to increase performance: i) mechanical polishing, ii) mechanical polishing combined with a strong plasma etching, and iii) mechanical polishing coupled to both a weak plasma etching and a Ti1−yAly metallic interlayer deposition. Then, all the specimens were cyclically heat treated up to 200 cycles at 950 °C, using a Burner Rig (BR) facility.The chosen Ti1−xAlxN/substrate interface architecture considerably influenced average compressive residual stress (Sres) and adhesion of just deposited films. Moreover, it was possible to identify a clear relationship between Sres behavior and each coating comportment after BR tests. It became clear that the weak plasma etching/Ti1−yAly interlayer match helped improving the system stability (i.e. very low average residual stress thermal relaxation) thus guarantying high temperature oxidation resistance.

Synergistic effect of low and high intensity ultrasonic irradiation on the direct growth of ZnO nanostructures on the galvanized steel surface: investigation of the corrosion behavior

Considering the current interest in the preparation of modified surfaces with fixed nanostructures, in this research, the hot water treatment was chosen as a simple and efficient procedure for the direct growth of ZnO nanostructures (ZnO NSs) on the metallic surface. To improve the method and reduce the cost of experiments, the commercial galvanized steel (steel containing a thin layer of zinc) was used as the base substrate. The use of the galvanized steel as an inexpensive and available metal surface has advantages compared to the pure Zn foil (used in other researches). In addition, in the present work, the effective pretreatment of the base substrate surface by applying the chemical etching under the low intensity ultrasonic irradiation facilitated the reaction progress (Zn → ZnO) in a shorter time and relatively low temperature in comparison to many reports. To find the effect of acoustic energy on the final ZnO morphology, the hot water treatment was carried out under conventional and sonochemical conditions. Finally, as a practical application, resulting surfaces were coated with electroless Ni-P deposits and the effect of as-grown ZnO NSs (as the sublayer) on improvement in the corrosion protection of binary Ni-P deposits was evaluated by the electrochemical method.

Improvement of flux pinning in GdBa2Cu3O7−δ thin film by nanoscale ferromagnetic La0.67Sr0.33MnO3 pretreatment of substrate surface

The present paper presents the effects of ferromagnetic La0.67Sr0.33MnO3 (LSMO) nanoparticles on the pinning characteristics of an epitaxial GdBa2Cu3O7−δ ((Gd) BCO) film deposited on top. LSMO nanoparticles with the size between 10 and 20nm were obtained on a (001) STO substrate by RF sputtering method. The analyses of magnetic measurements revealed that the presence of a complex vortex pinning mechanism within the (Gd) BCO film deposited on the undecorated substrate. With respect to a reference (Gd) BCO film, two additional pinning effects in LSMO decorated (Gd) BCO film were observed. One is the effect of the threading dislocations due to LSMO nanoparticles, and the other one is the LSMO nanoparticles itself. Like other nanosized particles, the LSMO nanoparticles on substrate will induce threading dislocations passing through the (Gd) BCO film. These threading dislocations serve as correlated pinning centers along the c-axis, which lead to the improvement of flux pinning properties in LSMO decorated (Gd) BCO film. According to the ferromagnetic property of LSMO material, a magnetic pinning mechanism was proposed to explain the significant increase of Jc and Fp values. The flux pinning abilities of LSMO nanoparticles were evaluated. The enhanced pinning characteristics in the high field region and high temperature together with the movement of H Fpmax (the corresponding field of Fpmax) also suggest a magnetic pinning mechanism for LSMO nanoparticles existed in LSMO decorated (Gd) BCO film.

Thin Metal Oxide Coatings for Lightweight Alloys

A new type of nanocomposite coating and its preparation technology was worked out1 and will be introduced in this presentation. The technology has two main steps – first, the working surface of substrate is anodized and second, the anodized base layer is covered with a thin toplayer, grown by atomic layer deposition method (ALD). Both steps of the coating preparation need special attention. The anodizing of a lightweight substrate, e.g. an aluminum alloy must result in a homogeneous by both thickness and composition anodic layer, and must consist as little as possible cracks and pores. It is well known that the anodic layer consist nanometric pores and at least part of them is reaching the substrate metal part and these are the weakest points of the anodized coating. Thus, the pores must be firmly sealed and even better filled up to the bottom with a corrosion resistant material. This can be achieved with the help of ALD that is a cyclic analogue of chemical vapor deposition method. In the presentation we will demonstrate how the new coating is prepared for Al2024 alloy, which is tending to pitting corrosion due to existing in it Cu-rich and other intermetallic particles, often with micrometer dimensions, part of them laying in near-surface region of the substrate.In the presentation we will go through the substrate surface pretreatment, anodizing and following ALD growth of nanolaminate of metal oxides as top part of the coating. The process gives micron thick composed coating with filled nanopores, see the scheme, and that coating withstand several thousand hours’ immersion in salt solution. Similar technique was used for protection Ti5 alloy substrates. In the presentation will be discussed surface pretreatment, anodizing and following ALD process, which gives micron thick composed coating with filled nanopores, see the scheme, and which withstand several thousand hours’ immersion in salt solution. Similar technique was used for protection Ti5 alloy substrates. In the presentation will be discussed surface pretreatment, anodizing and following ALD process, which gives micron thick composed coating with filled nanopores, see the scheme, and which withstand several thousand hours’ immersion in salt solution. Similar technique was used for protection Ti5 alloy substrates. L. A. thanks the European Social Funds of Doctoral Studies This work was also supported by the Estonian ME&S by projects IUT2-24, TK117 and TK141. Reference: V. Sammelselg, M. Merisalu, L. Aarik, Method of preparing corrosion resistant coatings, WO 2014102758 A1/GB2509335 A, Priority date 31.12.2012 (http://www.google.com/patents/WO2014102758A1?cl=en). Figure 1

Electron-diffraction study of graphene-film growth stages during the thermal destruction of 6H-SiC (000 $$\bar 1$$ ) in vacuum

The structure of graphene layers grown by sublimation on a 6H-SiC (000\(\bar 1\)) substrate surface is studied by electron diffraction depending on the sublimation temperature and substrate-surface pretreatment method. It is shown that the use of polishing sublimation etching of the substrate before thermal destruction at a temperature of 1350°C on the substrate surface results in the formation of single-crystal graphene domains with graphene-lattice rotation by 30° with respect to the SiC lattice and a small fraction of amorphous domains. An increase in the temperature to 1500°C leads to the partial formation of a polycrystalline graphene phase with turbostratic structure while retaining the preferred orientation of graphene crystallites as at 1350°C. The use of pregrowth annealing before thermal destruction makes it possible to grow a graphene film with a more ordered and homogeneous structure without inclusions of amorphous and polycrystalline components. The preferred orientation of graphene domains in the film remains unchanged.

WC-Co substrate preparation and deposition conditions for high adhesion of CVD diamond coating

Different substrate surface pretreatments have been used to improve the adhesion of CVD diamond coatings on WC-Co substrates. In this paper, we report the results of our experiments using a pretreatment method based on two-step chemical etching: one in Murakami solution and another in aqua regia. A systematic study was performed to evaluate the influence of the pretreatment on the composition and morphology of the WC-Co substrate. Furthermore, the effect of diamond nanoparticle seeding on the morphology and roughness of the substrate was also analyzed. After these studies, diamond coating was deposited on seeded WC-Co substrate by hot-filament CVD. The characterization of the CVD diamond coating was performed by Raman spectroscopy, FEG-SEM and AFM. Rockwell C indentation test was used to evaluate the adhesion between the CVD diamond coating and the WC-Co substrate.

Effects of substrate on the domains and electrical properties of epitaxial graphene formed on on-axis C-face 4H-SiC

The effect of substrate surface preparation on the quality of epitaxial graphene grown on on-axis C-face 4H-SiC has been investigated. Structural epitaxial graphene has been achieved using a graphite enclosure. The homogeneity and domain size of epitaxial graphene on different pretreated substrates were studied using Raman spectroscopy, field emission scanning electron microscopy and hall measurements. The etching of C-face SiC substrate using C3H8/H2 is shown to have a pronounced effect on the domain size and hall mobility of multilayer epitaxial graphene. From Raman measurements, it is found that the pretreatment of substrate has a great influence on the domain size of epitaxial graphene. From hall results, it is found that the effect of substrate pretreatment on carrier mobility follows the same tendency reflected in the results of Raman spectra. It is concluded that the pretreatment of substrate surface, mainly the etching for generating high density, regular and periodic step structure with flatter terrace, would allow the growth of graphene with significantly large area and high mobility, even on large on-axis C-face 4H-SiC wafer.

Influence of laser substrate pretreatment on anti-adhesive wear properties of WC/Co-based TiAlN coatings against AISI 316 stainless steel

To improve the anti-adhesive wear properties of WC/Co-based TiAlN coatings, a laser substrate surface pretreatment was examined. The cemented carbide substrates were textured with a Nd:YAG laser, in three different scanning speeds, and then coated with a PVD TiAlN film. The anti-adhesive wear properties of each surface were evaluated via the ball-on-disk wear test and turning experiments. Additionally, characterization tests such as variable depth scratch test were also performed in order to verify the coating adhesiveness and to explain the results of the wear and machining tests. The results reveal that the anti-adhesive wear properties of the three TiAlN coated textured samples are significantly improved over that of the conventional one; the adhesion of TiAlN coatings is greatly improved by using Nd:YAG laser substrate pretreatment. Moreover, laser-scanning speed has a profound effect on the adhesion strength of the pretreated samples. In the experiments, the lowest scanning speed (5mm/s) is most effective in providing a greater mechanical locking of the coatings upon the substrate and a more matching chemical property between substrate and coating materials, thus increasing the critical load of the coatings. Meanwhile, the adhered workpiece material layer is more stable on the pretreated sample irradiated at 5mm/s. Hence, potential wear protecting properties of the in-situ formed layer can be conserved.

Influence of plasma pretreatment on the performance of industrial tungsten carbide coatings deposited at low temperature on 100Cr6 bearing steel substrates

Abstract The study concerns different surface pretreatment procedures of the 100Cr6 bearing steel substrates using DC magnetron sputtering and high-power impulse magnetron sputtering. The influence of the pretreatment technique on structure, adhesion and overall performance of the deposited tungsten carbide tribological coatings is characterized. The substrate pretreatment and deposition processes are maintained at process temperatures lower than 180 °C in order not to affect the intrinsic structural and mechanical properties of the bearing steel substrates. It is shown that the pretreatment method does not influence the structure and composition of the coatings. On the other hand, it strongly affects the surface structure and more important the adhesion and the tribological properties of the coatings. It is shown that the high-power impulse magnetron sputtering technique in combination with a high bias voltage can be a valuable tool for substrate surface pretreatment to obtain a good adhesion even at low process temperature.

Substrate polarity and surface pretreatment temperature dependence of ZnO homoepitaxy

We have grown ZnO films on Zn-polar and O-polar ZnO substrates pretreated at different temperature by metal-organic chemical vapor deposition. Generally, the Zn-polar samples have better structural and optical properties than the O-polar samples. We also found that the Zn-polar samples have a great performance on the suppression of the unintentionally doped carbon impurities. The sample grown on the 1000°C-pretreated ZnO substrate has clearly showed a step-flow growth mode with the surface roughness as low as 2.654nm, which could be regarded as the best growth condition.

Effect of substrate surface pretreatment and annealing treatment on morphology, structure, optical and electrical properties of sputtered ZnO films

ZnO films were deposited on glass substrates at room temperature by RF magnetron sputtering method. Prior to the deposition, the glass substrates were pretreated with Al target in Ar or Ar/O2 ambient by DC magnetron sputtering. After pretreatment, the glass substrate are still very transparent and no metallic luster. AFM shows that RMS has a very slight change. XPS shows that no Al–O bonds exist in ZnO films. Cauchy fitting model shows that no Al or Al2O3 thin layer is formed between thin film and glass substrate. However, the pretreatment forms some isolated Al or Al2O3 grains and changes the micro-structure of substrate slightly, which lead to different lattice, stress and properties of ZnO films. Interestingly, combining the pretreatment and annealing treatment, the sum of 2θ or lattice constant c between as-grown and annealed samples is equal. The average transmission of all samples is over 85% in the wavelength range of 400–1000nm. The band gap energies of all samples are in range of 3.23–3.26eV. According to PL, three main blue emission peaks located at about 437–438, 444 and 456nm were observed in the S1 and S2 with the pretreatment. However, the wavelength range of the blue peaks of S3 without pretreatment was observed to narrow down, and peaks are located at about 444, 450 and 456nm. The lowest resistivity and highest carrier concentration of S1 are 5.29∗10−5Ωcm and 3.9805∗1022cm−3 respectively. The conductivity of ZnO films can be converted from n-type to p-type by different substrate surface treatment. It is noteworthy that with the unit cell elongation along c-axis, compressive stress and mass difference between as-grown and annealed films increases, while refractive index and PL intensity decreases. The lattice constant c and compressive stress are mainly effect factors of thermal stability and optical properties of ZnO film. The binding energy (BE) of Zn2p3/2 and Zn2p1/2 of as-grown and annealed S1 are 1019.4 and 1019.3, and 1042.5 and 1042.4eV, respectively. The BEs of O1s of as-grown and annealed S1 are relatively low, 529.2 and 528.9eV, respectively.

Growth and Characterization of Uniform Carbon Nanotube Arrays on Active Substrates

ABSTRACTCarbon nanotubes (CNTs) have unique thermal/electrical/mechanical properties and high aspect ratios. Growth of CNTs directly onto reactive material substrates (such as metals and carbon based foam structures, etc.) to create a micro-carbon composite layer on the surface has many advantages: possible elimination of processing steps and resistive junctions, provision of a thermally conductive transition layer between materials of varying thermal expansion coefficients, etc. Compared to growing CNTs on conventional inert substrates such as SiO2, direct growth of CNTs onto reactive substrates is significantly more challenging. Namely, control of CNT growth, structure, and morphology has proven difficult due to the diffusion of metallic catalysts into the substrate during CNT synthesis conditions. In this study, using a chemical vapor deposition method, uniform CNT layers were successfully grown on copper foil and carbon foam substrates that were pre-coated with an appropriate buffer layer such as Al2O3 or Al. SEM images indicated that growth conditions and, most notably, substrate surface pre-treatment all influence CNT growth and layer structure/morphology. The SEM images and pull-off testing results revealed that relatively strong bonding existed between the CNT layer and substrate material, and that normal interfacial adhesion (0.2‒0.5 MPa) was affected by the buffer layer thickness. Additionally, the thermal properties of the CNT/substrate structure were evaluated using a laser flash technique, which showed that the CNT layer can reduce thermal resistance when used as a thermal interface material between bonded layers.

Interfacial bonding features of Ni coating on Al substrate with different surface pretreatments in cold spray

The effect of the substrate surface pretreatment on the Ni–Al interfacial bonding features in cold spray was investigated. Oxide-free interfacial area is found to be the essential factor that affects the interfacial atomic diffusion and metallurgical bonding. Voids are formed at the interface between the particle and grit-blasted substrates, significantly reducing the oxide-free interfacial area. However, those voids cannot be found at the interface between the particle and polished and ground substrates. Therefore, the polished and ground substrates can provide higher coating mass and coating-substrate bonding strength than the grit-blasted ones.

Adhesion Assessment of BNT Films on Titanium Substrates Using a Scratch Test

Lead-free piezoelectric (Bi1/2Na1/2)TiO3 (BNT) films were deposited on 0.2 mm thick pure titanium (Ti) substrates by a hydrothermal method. Scratch tests were performed to quantitatively assess the adhesion strength between BNT films and Ti substrates. Ti substrates were pretreated by chemical polish and mechanical polish respectively prior to BNT film deposition with a view of investigating the effects of substrate surface pretreatments on the adhesion of BNT film. In the scratch test, the behaviour of BNT film exfoliation was investigated by SEM observation. The scratch test results revealed that the chemical polish pretreatment effectively improved the adhesion of BNT films.

Magneto-optics of nanoscale Bi:YIG films

Magnetic circular dichroism in the spectral region from 270 to 850 nm and Faraday rotation at the wavelength of 655 nm in ultrathin (1.5-92.8 nm) films prepared by reactive ion beam sputtering of target of nominal composition Bi2.8Y0.2Fe5O12 were studied. The observed effects of the "blue shift," inversion of the signs and change in the intensity of magneto-optical transitions, are discussed. It is demonstrated that all studied nanoscale films reveal magnetic properties-and their composition depends on the method of substrate surface pretreatment.

Large-area, highly oriented lamellar block copolymer nanopatterning directed by graphoepitaxially assembled cylinder nanopatterns

We present a large-area, highly aligned lamellar block copolymer self-assembly directed by graphoepitaxially aligned cylinder block copolymer self-assembly. Asymmetric block copolymer thin films were graphoepitaxially assembled within 1 μm wide parallel photoresist trenches to generate surface-parallel nanocylinder arrays. After the graphoepitaxial morphology was frozen by a radiative treatment, a thin film of symmetric block copolymer was deposited over the nanocylinder array, where the lamellar period was consistent with the period of the underlying cylinder array. Subsequent thermal annealing generated highly aligned lamellar morphology over a large area without any trace of an underlying photoresist pattern. Our method employing surface-parallel cylinder self-assembly as a structure-directing chemical pattern for epitaxial self-assembly does not require any substrate surface pretreatment and is, thus, highly efficient for nanopatterning various substrates.