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سال ۱۳۹۷ سال حمایت از کالای ایرانی گرامی باد

Surface and Coatings Technology

  1. Process parameter optimisation of laser clad iron based alloy: Predictive models of deposition efficiency, porosity and dilution

    Publication date: 15 September 2018
    Source:Surface and Coatings Technology, Volume 349

    Author(s): L. Reddy, S.P. Preston, P.H. Shipway, C. Davis, T. Hussain

    As a candidate coating material for heat-exchanger surfaces in commercial power generation boiler, an amorphous/glass forming Fe-Cr-B alloy NanoSteel SHS 7170 was deposited by a 2 kW fibre laser onto a boiler grade steel substrate (15Mo3). A comprehensive trial with 28 single track optimisation runs was carried out to develop models of the influence of three processing parameters, laser power, laser traverse speed and powder feed rate, on powder deposition efficiency, dilution and porosity. It was found that deposition efficiency is dependent on laser power and powder feed rate, increasing with increasing power and decreasing powder feed rate when tested within the parameter window of laser power ranging from 0.4 to 2 kW; traverse speed varying from 150 to 1200 mm min‑1; and powder feed rate varying from 4 to 10 g min‑1. Similarly, it was found that dilution is also dependent on laser power and powder feed rate. Dilution increases with increasing power and decreases with increasing powder feed rate within the same parameter window discussed above. This means that through processing parameter selection, these properties can be adjusted to suit their application. Porosity was found to be independent of processing parameters and instead mostly dependent on the feedstock material. A model was produced for predicting porosity within a powder feedstock, found to be 8.5%. These models were used to successfully produce an optimised coating.

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  2. Pulsed laser deposition of crystalline garnet waveguides at a growth rate of 20μm per hour

    Publication date: 15 June 2018
    Source:Surface and Coatings Technology, Volume 343

    Author(s): James A. Grant-Jacob, Stephen J. Beecher, Jake J. Prentice, David P. Shepherd, Jacob I. Mackenzie, Robert W. Eason

    We report pulsed laser deposition of high-quality crystalline yttrium aluminium oxide and yttrium gallium oxide with a growth rate approaching 20μm per hour by using an excimer laser operating at a repetition rate of 100Hz. This result demonstrates the capability of PLD at 100Hz for upscaling deposition speeds to a rate that is industrially relevant. In addition, we show that use of this high repetition rate can cause additional heating of the substrate, which in turn affects the film composition. This effect is used as an additional control parameter on the composition, and thus refractive index, of the grown material.

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  3. Low temperature thin films for next-generation microelectronics (invited)

    Publication date: 15 June 2018
    Source:Surface and Coatings Technology, Volume 343

    Author(s): Jurriaan Schmitz

    In this article the current methodologies for low-temperature thin film deposition in microelectronics are reviewed. The paper discusses the high temperature processes in microchip manufacturing and describes the thermal budget fitting issue. The quest for low temperature deposition techniques is motivated in the perspective of contemporary trends in microchip technology such as 3D integration and the ending miniaturization. Reduced temperature depositions tend to deliver lower quality films. This is illustrated with the relation between deposition temperature and thin dielectric film quality (dielectric strength). Existing and emerging technologies for low-temperature thin film deposition are reviewed with an emphasis on their applicability in microelectronic fabrication.





  4. The role of carrier gas flow in roll-to-roll AP-PECVD synthesized silica moisture barrier films

    Publication date: 15 April 2018
    Source:Surface and Coatings Technology, Volume 339

    Author(s): A.S. Meshkova, F.M. Elam, S.A. Starostin, M.C.M. van de Sanden, H.W. de Vries

    Moisture barrier films are deposited on a polymer foil by roll-to-roll Atmospheric Pressure Plasma Enhanced CVD reactor using a N2, O2, TEOS gas mixture. The film microstructure and permeation properties are studied as a function of the carrier gas flow rate with both static and dynamic film transport. The microstructure is analyzed by spatially resolved attenuated total reflectance (ATR)-FTIR and correlated with the vertical density gradient obtained in the dynamic films and the moisture barrier performance. It is shown that by varying the carrier gas flow rate the vertical density gradient, or the network porosity, can be tuned by governing the convective transport inside the reactor consequently densifying the inorganic film at fixed energy cost (i.e. Yasuda parameter) of the process. Moreover, adopting the bilayer architecture allows to achieve the same moisture barrier properties of 2 · 10−3 g·m−2·day−1 (40 °C, 90% RH) at only half the film thickness of a single layer barrier films, which consequently leads to a throughput increase of almost two times.





  5. Chemical vapor deposition of TiN on transition metal substrates

    Publication date: 25 January 2018
    Source:Surface and Coatings Technology, Volume 334

    Author(s): L. von Fieandt, T. Larsson, E. Lindahl, O. Bäcke, M. Boman

    The growth of chemical vapor deposited TiN from a reaction gas mixture of TiCl4, N2 and H2 was investigated on three different transition metal substrates: Fe, Co and Ni at deposition temperatures ranging from 850°C to 950°C. The interactions between the substrate metals and the gas phase were investigated using thermodynamic calculations. The TiN coatings were characterized by scanning electron microscopy, scanning transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and transmission Kikuchi diffraction. Chemical vapor deposition (CVD) of TiN on Co substrates resulted in dense, columnar coatings of single phase TiN. The activation energy for TiN deposition on Co was determined to be 90kJ/mol. CVD of TiN on Fe substrates caused severe substrate corrosion by the formation of gaseous FeClx. Due to the substrate corrosion, the activation energy could not be determined. Furthermore, it was found that CVD of TiN on Ni substrates produced a phase mixture of TiN and Ni3Ti. Formation of Ni3Ti could be minimized by decreasing the H2 partial pressure and increasing the N2 partial pressure. Deposition on Ni yielded two different activation energies, 40kJ/mol in the temperature interval 850°C to 900°C and 165kJ/mol in the interval 900°C to 950°C. This is an indication of two different types of process control, which were identified as Ni diffusion into the growing film and a gas phase processes. The results of the present study showed that CVD of TiN on a cemented carbide using Fe and Ni in the binder phase, must be optimized in order to avoid corrosion or unwanted phases. Methods to achieve this are presented in this paper.





  6. Laser-based process for polymeric tribological coatings on lightweight components

    Publication date: 25 December 2017
    Source:Surface and Coatings Technology, Volume 332

    Author(s): Hendrik Sändker, Jochen Stollenwerk, Peter Loosen

    Due to excellent material properties, coatings based on high-temperature resisting thermoplastic polymers like PEEK (polyether ether ketone) represent a promising alternative to conventional tribological coatings based on sliding lacquer. Since the conventional, oven-based coating process requires heating the entire component above the melting temperature of PEEK (approx. 340°C), it is not suitable for temperature-sensitive base materials (e.g. aluminum alloy AlMgSi1). Hence, with the objective of significantly reducing the thermal load of the workpiece and enhancing the process energy efficiency, a laser-based coating process is investigated by the authors. The current research is primarily focused on the process development for the two laser-based process steps. Firstly, the influence of a laser pre-treatment on the surface topography and the adhesion of the PEEK coating is investigated. Secondly, the laser-based coating process is evaluated with regard to the relative density of the coating. As a result, dense and adherent tribological coatings can be applied on aluminum substrates. The adherence is significantly increased by a laser-based pre-treatment of the substrates. The minimal interaction time for generating dense coatings is approximately 7s which represents a decrease by a factor of >100 in comparison to oven processing.





  7. Experimental study of high velocity oxy-fuel sprayed WC-17Co coatings applied on complex geometries. Part B: Influence of kinematic spray parameters on microstructure, phase composition and decarburization of the coatings

    Publication date: 15 November 2017
    Source:Surface and Coatings Technology, Volume 328

    Author(s): Vasileios Katranidis, Sai Gu, Tomas Ramirez Reina, Esat Alpay, Bryan Allcock, Spyros Kamnis

    The aim of this study is to evaluate comprehensively the effect of spray angle, spray distance and gun traverse speed on the microstructure and phase composition of HVOF sprayed WC-17 coatings. An experimental setup that enables the isolation of each one of the kinematic parameters and the systemic study of their interplay is employed. A mechanism of particle partition and WC-cluster rebounding at short distances and oblique spray angles is proposed. It is revealed that small angle inclinations benefit notably the WC distribution in the coatings sprayed at long stand-off distances. Gun traverse speed, affects the oxygen content in the coating via cumulative superficial oxide scales formed on the as-sprayed coating surface during deposition. Metallic W continuous rims are seen to engulf small splats, suggesting crystallization that occurred in-flight.





  8. Study of the effect of RF-power and process pressure on the morphology of copper and titanium sputtered by ICIS

    Publication date: 25 October 2017
    Source:Surface and Coatings Technology, Volume 327

    Author(s): Daniel A.L. Loch, Arutiun P. Ehiasarian

    Inductively coupled impulse sputtering is a promising new technique for highly ionised sputter deposition of materials. It combines pulsed RF-power ICP technology to generate plasma with pulsed high voltage DC bias on the cathode to eliminate the need for a magnetron. To understand the effect of power and pressure on the coating morphology, copper and titanium films have been deposited in a power-pressure matrix. The RF-power was increased from 2000 to 4000W. The pressure was set to 6Pa and 13Pa respectively. For copper, the morphology changes from columnar to fully dense with increasing power and the deposition rate drops from 360nmh−1 to 210nmh−1 with higher process pressure. Titanium morphology does not change with power or pressure. The deposition rate is lower than predicted by the differences in sputtering yields at 68nmh−1 for a pressure of 6Pa.





  9. Control over fine scale terrace structures induced on polycrystalline Pd by simple heat treatments in air

    Publication date: 15 October 2017
    Source:Surface and Coatings Technology, Volume 326, Part A

    Author(s): J.M. Sobral, T.W. Clyne, R. Rezk, A.E. Markaki

    This paper presents information about the formation of terraces (often composed of relatively wide faces and relatively narrow steps between them) on samples of polycrystalline palladium. These have been formed via simple heat treatments, involving holding at 1200°C for periods ranging from a few minutes to several hours, followed by quenching by jets of inert gas. These treatments are such that the terraces are created, and survive the cooling, without significant formation of surface oxide. The crystallographic anisotropy of the surface energy is the driving force for terrace formation, with low surface energy planes tending to be preferentially exposed. Information is presented regarding the surface topography of the terraces and of the grain boundary regions, which have mainly been explored using AFM. Typically, the step heights are of the order of 50nm and the widths of the faces between them are around 1μm, although there are quite substantial local variations in these figures. It is shown that a degree of control is possible via the grain structure and texture of the sample, as well as via the processing conditions during the terracing treatment.

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  10. RETRACTED: Cross- and in-plane thermal conductivity of AlN thin films measured using differential 3-omega method

    Publication date: 25 June 2017
    Source:Surface and Coatings Technology, Volume 320

    Author(s): Manuel Bogner, Günther Benstetter, Yong Qing Fu

    This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief and the corresponding author. The corresponding author has misused Fig. 6 and Fig. 7. Figure 6 shows three surfaces of AlN layers on silicon obtained by Atomic Force Microscopy (AFM), while Fig. 7 presents a respective example of a cross-section obtained by Transmission Electron Microscopy (TEM). Both were published previously in a different form (https://doi.org/10.1063/1.4748048.) and were manipulated and misused in the present paper. The corresponding author, Manuel Bogner, has taken full responsibility for the misuse of the images and apologizes for the academic misconduct.





  11. Synthesis and characterization of thermally evaporated copper bismuth sulphide thin films

    Publication date: 25 June 2017
    Source:Surface and Coatings Technology, Volume 320

    Author(s): Arshad Hussain, R. Ahmed, Nisar Ali, Naser M AbdEl-Salam, Karim bin Deraman, Yong Qing Fu

    Non-toxic copper containing chalcogenides are considered as promising alternate materials for the absorber layer in thin film solar cells and visible-light harvesting devices. In this paper, we reported synthesis of Cu3BiS3 thin films using a two-step thermal evaporation method for the first time. A Cu2S layer of 0.4μm thickness was firstly evaporated onto glass substrate at room temperature, followed by evaporation of a Bi2S3 layer of 0.8μm thickness. The Cu3BiS3 thin films were formed by thermally annealing and diffusing the two evaporated layers in a vacuum furnace. This method resulted in the improved crystallinity and phase purity of the grown Cu3BiS3 films. Effects of annealing temperature on different properties of the fabricated samples were investigated. The obtained low band-gap (1.45eV) and good optical properties such as low transmittance (10–30%) and reflectance (~10%) of the Cu3BiS3 films demonstrated it as a suitable material for the absorber layer of solar cells.





  12. Experimental study of high velocity oxy-fuel sprayed WC-17Co coatings applied on complex geometries. Part A: Influence of kinematic spray parameters on thickness, porosity, residual stresses and microhardness

    Publication date: 15 February 2017
    Source:Surface and Coatings Technology, Volume 311

    Author(s): Vasileios Katranidis, Sai Gu, Bryan Allcock, Spyros Kamnis

    When a complex geometry is rotated in front of the thermal spray gun, the following kinematic parameters vary in a coupled fashion dictated by the geometry: Stand-off distance, spray angle and gun traverse speed. These fluctuations affect the conditions of particle impact with major implications on the coating's properties. This work aims to probe into the interplay and isolated effect of these parameters on vital coating characteristics in applications requiring variable stand-off distance and spray angles. WC-17Co powders are sprayed via HVOF on steel substrates in a set of experiments that simulates the spray process of a non-circular cross section, while it allows for individual control of the kinematic parameters. Comprehensive investigation of their influence is made on deposition rate, residual stresses, porosity and microhardness of the final coating. It was determined that oblique spray angles and long stand-off distances compromise the coating properties but in some cases, the interplay of the kinematic parameters produced non-linear behaviours. Microhardness is related negatively with oblique spray angles at short distances while a positive correlation emerges as the stand-off distance is increased. Porosity and residual stresses are sensitive to the spray angle only in relatively short stand-off distances.





  13. The effect of pure aluminum cold spray coating on corrosion and corrosion fatigue of magnesium (3% Al-1% Zn) extrusion

    Publication date: 15 January 2017
    Source:Surface and Coatings Technology, Volume 309

    Author(s): Mohammad Diab, Xin Pang, Hamid Jahed

    Pure aluminum powder was successfully sprayed on AZ31B extrusion flat and round coupons at low temperature. The corrosion and corrosion fatigue behavior of the coated and uncoated samples were examined by performing accelerated corrosion tests. The corrosion resistance of AZ31B samples with and without coating was investigated based on ASTM B117 standard salt spray with a concentration of 5% NaCl at 36°C, 100% relative humidity. The corrosion fatigue of bare and coated round samples was examined by producing a thin film of 3.5% NaCl solution on the surface of the fatigue samples via integrating a corrosion chamber into a rotating bending fatigue testing machine. Pure Al coating provided significant corrosion protection for AZ31B in 5% NaCl fog environment by improving its corrosion resistance from 90% average weight loss in 33days for bare samples to <10% average weight loss in 90days of continuous corrosion cycles. However, pure Al coating did not improve the corrosion fatigue strength of magnesium and samples with and without coating showed similar corrosion fatigue trends. Test results in salt solution showed fatigue life reduction of 88% when compared with test results in air. The microstructure examination of samples failed under cyclic load showed early cracking of Al coat which allowed the electrolyte penetration into Mg substrate creating a localized corrosion and premature failure. The early cracking was attributed to the lower fatigue strength of pure Al compared to AZ31B.





  14. Anodizing of aluminium and AA 2024-T3 alloy in chromic acid: Effects of sulphate on film growth

    Publication date: 15 January 2017
    Source:Surface and Coatings Technology, Volume 309

    Author(s): D. Elabar, G.R. La Monica, M. Santamaria, F. Di Quarto, P. Skeldon, G.E. Thompson

    Chromic acid anodizing is important for the corrosion protection of aerospace aluminium alloys. Previous study has demonstrated that SO4 2− impurity in the chromic acid affects the film growth on aluminium at a voltage of 100V. The present work further investigates aluminium and extends the study to industrial anodizing conditions (Bengough-Stuart (B-S) process) and to the AA 2024-T3 alloy. It is shown that SO4 2− concentrations between ~38–300ppm reduce the film growth rate for aluminium anodized at 100V in comparison with an electrolyte than contains ≤1.5ppm SO4 2−, whereas ~1500–3000ppm SO4 2 have an opposite effect and lead to an unstable pore diameter. Under the B-S process, the film growth depends on the substrate composition, the SO4 2− content of the film, the film morphology and, for the alloy, oxygen generation. Corrosion tests of the alloy in 3.5% NaCl solution revealed better protection with films formed in chromic acid containing 38ppm SO4 2− compared with ≤1.5ppm SO4 2−, which are within the specified limits for sulphate impurity for chromic acid anodizing. The difference in corrosion protection is proposed to be related to the observed differences in the film morphologies; it is speculated that this may influence the retention of residues of chromate ions in the films.





  15. Electrical discharge coating of nanostructured TiC-Fe cermets on 304 stainless steel

    Publication date: 15 December 2016
    Source:Surface and Coatings Technology, Volume 307, Part A

    Author(s): Samer J Algodi, James W Murray, Michael W Fay, Adam T Clare, Paul D Brown

    The electrical discharge coating (EDC) process, as used for the development of TiC-Fe cermet coatings on 304 stainless steel, has been investigated as a function of increasing current (2–19A) and pulse-on time (2–64μs). Coating morphologies, comprising of a mixture of TiC, γ-Fe, ά-Fe and amorphous carbon, were characterised using the combined techniques of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffractometry (XRD) and cross-sectional transmission electron microscopy (TEM). The developed coatings exhibited variable hardness values, up to an order of magnitude higher than that of the substrate, depending on the content and dispersion of nanostructured TiC particles within the Fe matrix. Coating hardness was found to increase with increasing current, but decrease under conditions of high pulse-on times, reflecting differences in the amount of TiC incorporated into the coatings. Optimised coatings were achieved using conditions of low processing energy which minimised the development of pores and cracks.





  16. Surface modification of mild steel using a combination of laser and electrochemical processes

    Publication date: 15 December 2016
    Source:Surface and Coatings Technology, Volume 307, Part A

    Author(s): Alistair Speidel, Adrian Hugh Alexander Lutey, Jonathon Mitchell-Smith, Graham A. Rance, Erica Liverani, Alessandro Ascari, Alessandro Fortunato, Adam Clare

    Traditional methods for achieving hierarchical surface structures include highly specified, deterministic approaches to create features to meet design intention. In this study microstructural alteration was undertaken using laser apparatus and secondary texturing was achieved via succeeding electrochemical processes. Electrochemical jet machining (EJM) was performed on mild steel subjected to laser pre-treatment using power densities of 4167 and 5556W/cm2 with pulse durations from 0.3–1.5s. Results show that in combination, laser pre-treatment and EJM can alter the exposed surface textures and chemistries. Here, machined surface roughness (Sa) was shown to increase from approximately 0.45μm for untreated surfaces to approximately 18μm for surfaces subjected to extreme laser pre-treatments. After pre-treatments materials were characterised to appraise microstructural changes, shown to be martensite formation, reinforced by complementary simulation data, and significant increases in observable hardness from approximately 261HV for the as-received material to over 700HV after pre-treatment. The greater hardness was retained after EJM. Exposed martensitic lath structures at machined surfaces are shown to be partially responsible for surface roughness increases. The surfaces were explored with energy dispersive X-ray spectroscopy (EDS) and Raman spectroscopy demonstrating changes in apparent surface chemistry. This analysis revealed increasing oxide formation at the surface of the pre-treated EJM surface, a further contributory factor to surface roughness increases. This new process chain will be of interest to manufacturers seeking to control surface morphology for applications including micro-injection mould/die manufacture. While demonstrated here for steel similar mechanisms are exploitable in other material systems. A new technique has been demonstrated, resulting from the models and processes presented to couple laser and electrolyte jet processing for complex surface preparation.





  17. Finite element study of the influence of hard coatings on hard metal tool loading during milling

    Publication date: 25 October 2016
    Source:Surface and Coatings Technology, Volume 304

    Author(s): Ivan Krajinović, Werner Daves, Michael Tkadletz, Tamara Teppernegg, Thomas Klünsner, Nina Schalk, Christian Mitterer, Christian Tritremmel, Werner Ecker, Christoph Czettl

    Within this work, a state-of-the-art Arbitrary Lagrangian-Eulerian finite element model of a milling operation using coated hard metal cutting inserts is presented. During milling, the cutting depth constantly decreases, thus, to obtain the correct cutting depth, the model considers movement of the tool in a vertical direction. The behavior of the 42CrMo4 workpiece material is described using a standard Johnson-Cook material model. A detailed tool model able to represent both an uncoated and coated tool is created. The tool model is based on an industrial hard coated fine-grained hard metal tool with 8wt.% Co. Three hard coatings are investigated: (i) an arc evaporated TiAlN single layer, (ii) a chemical vapor deposited TiCN/α-Al2O3 bilayer and (iii) a chemical vapor deposited TiAlN/α-Al2O3 bilayer. An uncoated tool model is used as a reference to compare the results. The tool loading during milling is investigated. The calculated variables are cutting forces and the tool-workpiece contact length. The influence of the coatings on temperature, von Mises stress and accumulated equivalent plastic strain is simulated in the coating and the substrate. Measured and literature based thermal and mechanical material parameters are used to describe the material behavior of the coatings and the substrate.





  18. Wear resistant coatings of boron-modified stainless steels deposited by Plasma Transferred Arc

    Publication date: 25 September 2016
    Source:Surface and Coatings Technology, Volume 302

    Author(s): Erich Sigolo, Juliano Soyama, Guilherme Zepon, Claudio Shyinti Kiminami, Walter José Botta, Claudemiro Bolfarini

    In this research work the microstructure and wear resistance of boron-modified stainless steel coatings were investigated. The coatings were produced by Plasma Transferred Arc (PTA) with powders of supermartensitic and superduplex stainless steel with 1 and 3wt.% B addition, respectively. The deposition was carried out on AISI 4140 steel substrate. Microstructural characterization revealed dendritic growth in both cases; however, the amount of borides formed was quite different, around 14% for supermartensitic with 1wt.% B and 32% for superduplex with 3wt.% B. Thermodynamic calculations were used to predict phase formation and solidification paths resulting in good agreement with the experimental results. The wear resistance was characterized by dry sand/rubber wheel and reciprocating pin-on-plate tests. In dry sand/rubber wheel the volume loss of quenched and tempered AISI 4140 was superior to supermartensitic steel with 1wt.% B, nonetheless it was comparable to superduplex steel with 3wt.% B. On the other hand, regarding the pin-on-plate tests, the wear resistance of both boron-modified steels was far superior. The formation of hard borides increased both the hardness and overall wear resistance of boron-modified stainless steels. Additionally, the high boride fraction was responsible for the superior wear performance of superduplex with 3wt.% B.

    Graphical abstract






  19. Effects of angular injection, and effervescent atomization on high-velocity suspension flame spray process

    Publication date: 25 September 2016
    Source:Surface and Coatings Technology, Volume 302

    Author(s): Mahrukh Mahrukh, Arvind Kumar, Sai Gu

    This work presents the nanostructured coating formation using suspension thermal spraying through the HVOF torch. The nanostructured coating formation requires nanosize powder particles to be injected inside a thermal spray torch using liquid feedstock. The liquid feedstock needs to be atomized when injected into the high-velocity oxygen fuel (HVOF) torch. This paper presents the effects of angular injection and effervescent atomization of the liquid feedstock on gas and droplet dynamics, vaporization rate, and secondary breakup in the high-velocity suspension flame spray (HVSFS) process. Different angular injections are tested to obtain the optimum value of the angle of injection. Moreover, effervescent atomization technique based on twin-fluid injection has been studied to increase the efficiency of the HVSFS process. Different solid nanoparticle concentrations in suspension droplets are considered. In angular injection the droplets are injected into the core of the combustion zone; this immediately evaporates the droplets, and evaporation is completed within the torch. The value of 10°–15° is selected as the optimal angle of injection to improve the gas and droplet dynamics inside the torch, and to avoid the collision with the torch's wall. The efficiency of the effervescent atomization can be enhanced by using high gas-to-liquid mass flow rate ratio, to increase the spray cone angle for injecting the suspension liquid directly into the combustion flame. It is also found that the increment in the nanoparticle concentration has no considerable effects on the droplet disintegration process. However, the location of evaporation is significantly different for homogeneous and non-homogeneous droplets.





  20. Electrodeposition and biomineralization of nano-β-tricalcium phosphate on graphenated carbon nanotubes

    Publication date: 15 July 2016
    Source:Surface and Coatings Technology, Volume 297

    Author(s): N. Metoki, C.M.R. Rosa, H. Zanin, F.R. Marciano, N. Eliaz, A.O. Lobo

    Nano-calcium-phosphate (n-CaP) is an attractive, biocompatible material for increasing osteointegration. Among nanomaterials, functionalized carbon-based materials are emerging materials, which have excellent mechanical properties, biocompatibility and chemical stability. These properties may further enhance the n-CaP performance. It has been shown that stoichiometric n-CaP can be electrodeposited on graphene and carbon nanotubes (CNTs) by employing fast and low-cost electrodeposition techniques. Here, we present, for the first time, a crystalline, needle-like nano-β-tricalcium phosphate (n-β-TCP) electrodeposited on reduced graphene oxide (rGO) nanosheets. The rGO was grown on CNT, as a composite biomaterial, in a one-step process, followed by electrodeposition of n-CaP. The results show that, in acidic pH, needle-like crystals appear on the surface. It is speculated that the carboxyl (carboxylic acid)/carboxylate functional groups attached directly to the rGO are essential in accelerating OH– formation and deposition of needle-like n-CaP crystals. High-resolution scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction elucidated homogeneous, highly crystalline, n-CaP (β-tricalcium phosphate) crystals. This composite presented an excellent in vitro biomineralization after soaking in simulated body fluid.

    Graphical abstract