Optimum Deposition Conditions Research Articles

Optimisation & minimisation of corrosion rate of electroless Ni-Co-P coating

ABSTRACT Electroless Ni-Co–P alloy coatings were deposited to decrease the corrosion rate of the copper substrate. Central Composite Design (CCD) was employed through Design Expert Software to establish optimised deposition parameters, which produces a coating having high corrosion resistance. CCD has also been employed to determine the effect of various process parameters namely concentration of cobalt sulphate (CoSO4.7H2O) solution (10–20 gm/cc), concentration of sodium hypophosphite (NaH2PO2.H2O) solution (20–30 gm/cc) and bath temperature (80-90°C). The corrosion rate was determined by the Potential Dynamic test in 3.5% NaCl solution and the Tafel plot was used to determine the corrosion current density for each coated substrate. On the corrosion response of the coatings, the most significant interactions and important factors were identified using ANOVA analysis. The regression analysis showed a good fit of the experimental data through the second-order polynomial model with a coefficient of determination (R2) value of 0.9531 and a model F-value of 22.57. 15 g/L of Cobalt Sulphate, 30 g/L of Sodium Hypophosphite and 80°C of bath temperature were found out to be the optimum conditions of bath deposition to obtain a corrosion rate of 0.535 µm/Y.

Photocatalytic Properties of Thermally Annealed Films of Titanium Butoxide-=SUP=-*-=/SUP=-

We show that titanium dioxide particles capable of Reactive oxygen species generation can be produced in titanium butoxide films by annealing them at 500oC. Optimal conditions for the films deposition by a modified Langmuir-Blodgett technique were selected basing on the film uniformity examined by optical and electron microscopy. The photocatalytic activity of the annealed film was tested using RNO sensor bleaching.

Structure-Dependent Photoluminescence in Low-Dimensional Ethylammonium, Propylammonium, and Butylammonium Lead Iodide Perovskites.

Hybrid organic-inorganic perovskites have attracted great attention as the next generation materials for photovoltaic and light-emitting devices. However, their environment instability issue remains as the largest challenge for practical applications. Recently emerging two-dimensional (2D) perovskites with Ruddlesden-Popper structures are found to greatly improve the stability and aging problems. Furthermore, strong confinement of excitons in these natural quantum-well structures results in the distinct and narrow light emission in the visible spectral range, enabling the development of spectrally tunable light sources. Besides the strong quasi-monochromatic emission, some 2D perovskites composed of the specific organic cations and inorganic layer structures emit a pronounced broadband emission. Herein, we report the light-emitting properties and the degradation of low-dimensional perovskites consisting of the three shortest alkylammonium spacers, mono-ethylammonium (EA), n-propylammonium (PA), and n-butylammonium (BA). While (BA)2PbI4 is known to form well-oriented 2D thin films consisting of layers of corner-sharing PbI6 octahedra separated by a bilayer of BA cations, EA with shorter alkyl chains tends to form other types of lower-dimensional structures. Nevertheless, optical absorption edges of as-prepared fresh EAPbI3, (PA)2PbI4, and (BA)2PbI4 are obviously blue-shifted to 2.4-2.5 eV compared to their 3D counterpart, methylammonium lead iodide (MAPbI3) perovskite, and they all emit narrow excitonic photoluminescence. Furthermore, by carefully optimizing deposition conditions, we have achieved a predominantly 2D structure for (PA)2PbI4. However, unlike (BA)2PbI4, upon exposure to ambient environment, (PA)2PbI4 readily transforms to a different crystal structure, exhibiting a prominently broadband light from ∼500 to 800 nm and a gradual increase in intensity as structural transformation proceeds.

Opto-electrical properties and internal stress in Al:ZnO thin films deposited by direct current reactive sputtering

In this work we study the effect of the oxygen concentration, deposition temperature, and post-deposition annealing on the optical and electrical properties of Al:ZnO thin films deposited by direct current (DC) reactive sputtering. The internal stress in the thin film is also monitored in-situ during growth with a multi-beam optical stress sensor. This latter technique allows to have an insight on the growth mechanisms. Coupled with an analysis of the discharge curve, the optical transparency, the electrical conductivity, and the chemical composition of the films as a function of the oxygen concentration and temperature during deposition, it allows to estimate what are the optimal deposition conditions to minimize the resistivity and maximize the transparency. The analysis of the internal stress is also of interest because it can be a source of premature fracture or delamination of thin films. The internal stress can also change the intrinsic properties of a thin film. The influence of the stress on the resistivity is therefore studied for samples deposited in the different sputtering regimes.

Interfacial reinforcement of hybrid composite by electrophoretic deposition for vertically aligned carbon nanotubes on carbon fiber

In this paper, vertically aligned carbon nanotube/carbon fiber (VACNT/CF) hybrids was prepared by electrophoretic deposition (EPD) under mild conditions. The coaxial cylindrical electrode with CF filament as the cathode was employed to ensure dense VACNT arrays deposited on CF surface at low deposition voltage. The effect factors on the carbon nanoparticles alignment were investigated by the micro-morphology observations of hybrid fibers, including the diameter of carbon nanoparticles, types of solvent, deposition voltages, deposition time and the concentrations of carbon nanoparticles in dispersion. The results indicate that the optimum electrophoretic deposition conditions for vertically aligned hybrid fibers is the diameter of carbon nanoscale reinforcements of 110–170 mm, acetonitrile (ACN) as the dispersion medium, deposition voltage of 30 V, deposition time of 20 s and dispersion concentration of the carbon nanoparticles of 0.01 mg/mL. Single fiber tensile testing was performed and manifested that EPD in a coaxially cylindrical electric field was not destructive and could preserve the mechanical properties of CF filaments. Results of interphase properties tests demonstrated that the contact angle and the interfacial shear strength (IFSS) were significantly improved by 48.3% and 58.1% compared to that of as-recieved CF, respectively. The interfacial enhancement mechanism was also explored in details.

Atomically-smooth single-crystalline VO2 (101) thin films with sharp metal-insulator transition

Atomically-abrupt interfaces in transition metal oxide (TMO) heterostructures could host a variety of exotic condensed matter phases that may not be found in the bulk materials at equilibrium. A critical step in the development of such atomically-sharp interfaces is the deposition of atomically-smooth TMO thin films. Optimized deposition conditions exist for the growth of perovskite oxides. However, the deposition of rutile oxides, such as VO2, with atomic-layer precision has been challenging. In this work, we used pulsed laser deposition to grow atomically-smooth VO2 thin films on rutile TiO2 (101) substrates. We show that an optimal substrate preparation procedure followed by the deposition of VO2 films at a temperature conducive for step-flow growth mode is essential for achieving atomically-smooth VO2 films. The films deposited at optimal substrate temperatures show a step and terrace structure of the underlying TiO2 substrate. At lower deposition temperatures, there is a transition to a mixed growth mode comprised of island growth and layer-by-layer growth modes. VO2 films deposited at optimal substrate temperatures undergo a sharp metal to insulator transition, similar to that observed in bulk VO2, but at a transition temperature of ∼325K with ∼103 times increase in resistance.

Regulating Vertical Domain Distribution in Ruddlesden-Popper Perovskites for Electroluminescence Devices.

Efficient perovskite light-emitting diodes are designed by employing an ordered vertical domain distribution in quasi-two-dimensional (quasi-2D) perovskites to induce better electron flow to the emitting domains. Dimethyl sulfoxide is added to the precursor solution to tune the crystallization rate and promote the formation of high-m domains near the substrate surface via the one-step deposition method. Optimized deposition conditions yielding a film with favorable energetic landscape for both carrier injection and confinement results in a 4-fold external quantum efficiency (EQE) enhancement with maximum EQE of 5.79%. Better carrier injection is further supported by a turn-on voltage value that is comparable to the band gap of the emitter material (∼2.25 eV).

Low temperature growth of diamond-like nanocomposite films prepared by PACVD from Ar diluted siloxane plasma

Here, the diamond-like films in composite of nanostructure form are grown at low temperature (∼100 °C) from siloxane precursor incorporating silicon oxide (SiOx) moiety in amorphous carbon hydrogen (a-C:H) network using radio frequency plasma assisted chemical vapour deposition (rf-PACVD) method on various substances including ultra high molecular weight polyethylene (UHMWPE) substrates with the change in argon (Ar) carrier gas flow rate. The deposited diamond-like nanocomposite (DLN) films have been characterized using different spectroscopic techniques and tribological tests to understand the optimum deposition condition. The biocompatible nature of superior DLN film makes it a promising articulate knee and hip joint coating material.

Palygorskite modified with N-doped carbon for sensitive determination of lead(II) by differential pulse anodic stripping voltammetry.

A glassy carbon electrode (GCE) was coated with N-doped carbon-modified palygorskite and used as an electrochemical sensor for determination of Pb(II) by differential pulse anodic stripping voltammetry. To obtain high reproducibility and sensitivity, optimum experimental conditions for lead deposition are studied. Voltammetric responses of the modified GCE prepared with different ratios of carbon and palygorskite are examined under same conditions. Compared with a bare GCE, a N-doped carbon modified/GCE and a bismuth-modified GCE, N-doped carbon-modified palygorskite greatly improves the performance of GCE. Response is the best and the interfacial impedance is minimized if the fraction of carbon coating is 31%. This indicates that its performance is due to the synergies between palygorskite and N-doped carbon. Figures of merit for the modified GCE include (a) a preconcentration time of 180s, (b) a detection limit of 0.42μg·L-1 (2σ criterion), and (c) a linear response in the 4.0μg·L-1 to 10.0mg·L-1 Pb(II) concentration range. The method is successfully applied to the determination of Pb(II) in spiked tape water and gives recoveries between 97.1 and 104.3%. Graphical abstract Schematic representation of different adsorption sites of Pb(II) and the optimal carbon content. The wide detection range is attributed to the synergetic effect of N-doped carbon modified palygorskite.

Improvement of microstructures and properties of copper-aluminium oxide coating by pulse jet electrodeposition

Cu-Al2O3 nanocomposite coatings were jet electrodeposited using a direct current and pulse current to enhance the quality of the deposition and its mechanical properties. The composite coating prepared with a pulse current exhibited a smooth surface morphology, dense microstructure and good mechanical properties compared with those of the coatings obtained under direct current conditions. The effect of the pulse parameters, including the current density and pulse frequency, on the morphologies, microstructures, grain growth, and properties of the coatings was also examined. The results show that a high pulse frequency and appropriate current density improved the quality of the deposition and its mechanical properties. A dense nanocomposite copper-alumina deposited coating with an average refined grain size of 26 nm was fabricated with a pulse current density of 400 A dm−2 and a pulse frequency of 5000 Hz. The microhardness and tensile strength of the nanocomposite coating attained maximum values of 2.37 GPa and 692 MPa, respectively, when the optimum deposition conditions were used.

Conducting indium oxide films on plastic substrates by plasma enhanced reactive thermal evaporation

This work reports on low temperature deposition of conducting indium oxide films by a radio-frequency plasma enhanced reactive thermal evaporation (rf-PERTE) technique. The films were deposited on polyethylene terephthalate (PET) without intentional heating of the substrate and at elevated temperatures up to 150 °C. The material stoichiometry was accurately controlled by adjusting deposition conditions including the oxygen flow, process pressure, pumping speed, and RF-power. Besides, fine turning of the critical deposition parameters during the deposition was implemented by measuring the variation of film conductance in-situ. The film morphology was analyzed by scanning electron microscopy. Hall effect measurements were also performed to determine the relation between the deposition conditions and the electrical properties of the films. A resistivity of 4 × 10−4 Ω-cm was reached under optimized deposition conditions. A 250 nm-thick coating with 16 Ω/sq sheet resistance shows an 82% peak value of transmittance in the visible spectral range.

Modifying Carbon Felt Electrodes By Poly(o-toluidine) to Enhance the Performance of All-Vanadium Redox Flow Batteries

The overall cell performance of Vanadium Redox Flow Batteries (VRFB) is highly influenced by the physical and chemical properties of their carbon fibre electrodes1. Available as carbonized or graphitized carbon felts or carbon paper, they show relatively low electrochemical activity and poor wettability, which lead to many approaches to improve the surface properties, either by thermal treatment or surface modifications2–4. Previously, we studied the effect of several treatment methods on carbon felts5,6, as well as their impact on side reactions7. Sivakumar et al. utilized poly(o-toluidine) (POT) to enhance the electrochemical capacitance and conductivity of electrochemical capacitors by electrochemical deposition on carbon fabrics8. In this current study, we modified pristine and pre-treated, commercially available carbon felts (SIGRACELL® GFA6EA by SGL Carbon, Meitingen, Germany) by electrochemical polymerization and deposition of o-toluidine to increase the surface area and conductivity. The deposition of POT was carried out in 1 M H2SO4, containing 20 mM o-toluidine and controlled by a three-electrode setup with a carbon felt as working electrode, a Pt plate as counter electrode and an RHE reference electrode (Gaskatel Hydroflex). By varying the amount of cycles and the potential window, the amount of electrochemically polymerized and deposited POT can be controlled. The electrochemical activity towards vanadium was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The physical properties of the modified carbon felts were characterized via scanning electron microscopy, X-ray photoelectron spectroscopy and BET. The electrochemically most active, modified carbon felts were employed in a full redox flow cell (Scribner 857 redox flow test stand) and charge-discharge cycles at several current densities were performed. The electrochemical activity of thermally pre-treated carbon felts decreases, if the amount of deposited POT is too high and we found that the optimum deposition condition was one potentiodynamic cycle with 1 mV/s to 1.0 V vs. RHE in 20 mM o-toluidine in 1 M H2SO4. The cyclic voltammograms in Fig. 1(a) show the electrochemical activity towards the V4+/V5+ redox reaction of the felts in 0.1 M VOSO4 in 2 M H2SO4 at a scan rate of 5 mV/s. While the deposition of o-toluidine with a potentiodynamic cycling to 1.5 V vs. RHE show a reduced activity, one cycle with a limit of 1.0 V reduces the vanadium peak separation and increases the peak currents, which indicates an increased activity towards the V4+/V5+ redox reaction, compared to pristine samples. Fig. 1(b)-(d) show SEM images of the different degrees of POT deposition. After 10 cycles to 1.5 V vs. RHE (Fig. 1(c)), a thick coating of POT is visible on the fibres, whereas a potential limit of 1.0 V vs. RHE and 10 cycles (Fig. 1(d)) or 1 cycle (Fig. 1(e)) show a thin coating or scattered coated spots, respectively. A surface modification of carbon felts by electrochemically deposited o-toluidine was performed in this study. A slight coating of POT increases, whereas higher coatings reduce the electrochemical activity towards the V4+/V5+ redox reaction. The carbon felts were characterized by several techniques, as well as half cell and full cell cycling tests. In general, an increase in overall cell performance can be achieved by POT modified carbon felt electrodes. References C. Minke, U. Kunz, and T. Turek, J. Power Sources, 342, 116–124 (2017).Z. González et al., J. Power Sources, 338, 155–162 (2017).S. Rümmler et al., J. Electrochem. Soc., 165, A2510–A2518 (2018).B. Sun and M. Skyllas-Kazacos, Electrochim. Acta, 37, 1253–1260 (1992).L. Eifert, R. Banerjee, Z. Jusys, and R. Zeis, J. Electrochem. Soc., 165, A2577–A2586 (2018).R. Banerjee, N. Bevilacqua, L. Eifert, and R. Zeis, J. Energy Storage, 21, 163–171 (2019).L. Eifert, Z. Jusys, R. Banerjee, R. J. Behm, and R. Zeis, ACS Appl. Energy Mater., acsaem.8b01550 (2018).C. Sivakumar, J. N. Nian, and H. Teng, J. Power Sources, 144, 295–301 (2005). Figure 1

Copper Electrodeposition on Textile for Wearable Electronics

Two main tasks in fabricating a circuit is to pattern the interconnections and soldering elements to the patterned conductive traces. Using copper growth electrodeposition assisted by hydrogen evolution as a technique for integration of electronic elements and circuits in fabrics and flexible substrates particularly useful for soldering electronic components, representing an advantage over conventional methods and providing a high quality of the deposits requiring relatively inexpensive equipment. This method has shown high rate of deposition and formation of nanostructures, expected to anchor to the fibers of a fabric for enhanced stability of the structure. Moreover, the technique has proven to be reliable for soldering electronic components at room temperature. A copper pattern can be achieved over a MWCNTs coating by the copper growth deposition in the electrochemical cell after electrolysis is reached in the cell with the aqueous solution of Cu2+ and H2SO4. Cu2+ions interact with hydrogen allowing the formation of the reaction product by the application of voltages above 1.0V. The electrodeposition parameters and the quality of the copper being deposited will be analyzed to find the optimum conditions for fast copper deposition and adhesion to the fabric structure and also will be tested for soldering simple electronic elements and it will be studied to be more resilient during laundry.

Deposition of Ni(OH)2 on nickel substrate using vacuum kinetic spray and its application to high-performance supercapacitor

Herein, we report a direct deposition of nano-structured Ni(OH)2 from micro-sized Ni(OH)2 powder on nickel sheet and nickel foam using nano-particle deposition system, one of the low-vacuum and room temperature vacuum kinetic spray processes. In this work, the deposition of the Ni(OH)2 powder on nickel sheets is carried out with various stand-off-distances (SoDs) and carrier gas pressures. The deposited films are investigated by field-emission electron microscopy, X-ray diffraction, and Raman spectroscopy. The crystallite size of the nano-structured Ni(OH)2 depends on the SoD and the carrier gas pressure. The electrochemical performance of Ni(OH)2 deposited on nickel sheets is measured by cyclic voltammetry in the 3-electrode cell. The deposition with 5 mm SoD and 0.3 MPa carrier gas pressure is found to be the optimum deposition condition for the nano-structured Ni(OH)2 thin film as an electrode material. The nano-structured Ni(OH)2 thin film deposited with 5 mm SoD and 0.3 MPa carrier gas pressure on nickel foam demonstrates a specific capacitance of 2377 F g−1 at 2 mV s−1 scan rate and 2092 F g−1 at 1 A g−1 current density and excellent cyclic stability for 3000 cycles with 83% capacitance retention.

Impacts of preparation conditions on photoelectric properties of the ZnO:Ge transparent conductive thin films fabricated by pulsed laser deposition

Transparent conducting oxide (TCO) thin film is a key component of photoelectric devices for extensive applications. Exploring new TCO films with high electronic conductivity, high transmittance and low cost is urgently required. Here, the wurtzite structured Ge-doped ZnO thin films were deposited on the glass substrates by using a pulsed laser deposition method. The effects of Ge-doping concentration, glass substrate temperature and oxygen partial pressure on crystallinity, surface morphology, electrical conductivity and visible light optical transmittance of the thin films were studied systematically. It is revealed that the preferred orientation of the film can be controlled by oxygen partial pressure. Under the optimized deposition conditions of Ge-doping amount of 2.0 at.%, glass substrate temperature of 300 °C and oxygen partial pressure of 1.5 Pa, it was found that the prepared ZnO:Ge thin films with a thickness of 95 nm could display an electrical resistivity as low as 6.10 × 10−4 Ω cm and had a high transmittance of 92.3% in the visible region, proving that ZnO:Ge thin film is a promising TCO material.

Sprayed nanocrystalline ZMS thin films for nonlinear optical device applications

Growth and characterization of novel Zn(1-x)MgxS (ZMS) thin films for the nonlinear optical applications are reported here. ZMS thin films were deposited by industrial friendly spray pyrolysis method at optimized deposition conditions. XRD showed good crystallinity having crystallite size in the range 4.6–11 nm. It also confirmed the presence of mixed phases of zinc blende and wurtzite having strong orientation along (111) and (104) planes respectively. All the films have shown transmittance in the range 75%–90%. Detailed analysis of the transmittance data revealed a slight increase in the band gap from 3.42 eV to a maximum of 3.48 eV for 4 at% Mg doped thin films. Photoluminescence study confirmed the presence of intermediate bands in the doped thin films. Substantial change in third order optical susceptibility (χ(3)) and nonlinear refractive index (n2) values were observed for the doped films as compared to pristine samples. Remarkably, there was a flip from saturable absorption (SA) into the reverse saturation absorption (RSA) for the doped films. Z-scan studies showed that the spray deposited ZMS thin films are suitable for the nonlinear devices such as optical limiters and modulators.

Low friction coefficient of superhard nc-TiC/a-C:H nanocomposite coatings deposited by filtered cathodic vacuum arc

Nanocomposite coatings formed by metal (Ti, Al, Cr, etc)-doped diamond like carbon coatings can exhibit excellent tribological properties due to the combined improvement in hardness and toughness in optimized deposition conditions. In this work, Ti-doped a-C:H coatings are successfully deposited at C2H2 flow rate (fC2H2) of 50–250 sccm on Si (100) and AISI 304 L stainless steel substrates using filtered cathodic vacuum arc. Chemical bonding state, microstructure, and mechanical and tribological properties of Ti-doped a-C:H coatings were investigated using XPS, FESEM, nanoindentation and ball-on-disc tribometer, respectively. Nc-TiC/a-C:H nanocomposite coating with dense microstructure and smooth surface morphology are obtained at fC2H2 of 50–250 sccm thanks to high-efficiency magnetic filtered depositions. The sp2/sp3 ratio gradually decrease from 1.6 to 1.1, while (Ti–C)/(C–C) ratio shows a sharp decrease from 0.361 to 0.047. Hardness and H/E* and H3/E*2 ratios decrease from 41.2 GPa, 0.098 and 0.41 at 50 sccm to 22.9 GPa, 0.071 and 0.117 at 250 sccm, respectively. Residual stress ranges from −0.39 to −1.72 GPa. Superhard nc-TiC/a-C:H nanocomposite coating with the low residual stress, high H/E* and H3/E*2 exhibit low coefficient of friction of 0.07 and low wear rate of 5.4 × 10−9 mm3 N−1 m−1, which is ascribed to the high sp2/sp3 and (Ti–C)/(C–C) ratios, dense microstructure and smooth surface morphology.

Facile fabrication of nanostructured NiMo cathode for high-performance proton exchange membrane water electrolyzer

Clean hydrogen production via water electrolyzer connected with renewable energies is an essential technology for a sustainable energy in future. To realize the system, development of high-performance electrode remains a challenge. In this study, simple cathodic electrodepositions allow for the facile fabrication of a nanostructured non-noble metal cathode. Under optimized deposition condition, the NiMo catalyst supported by Cu foam exhibits overpotential of 68.7mV at −10mA/cm2 for hydrogen evolution reaction in acidic medium. The proton exchange membrane water electrolyzer employing the cathode demonstrates a remarkable current density of ˜2.0A/cm2 at 2.0V, which is the highest performance among state-of-the-art non-noble cathodes reported to date. The results presented herein indicate a promising cost-effective cathode for practical applications.

Electrodeposition of Platinum Catalyst from Ionic Liquids

The deposition of platinum from precursors dissolved in the ionic liquid 1-methyl-1-octylpyrrolidinium bis(trifluoromethylsulfonyl) imide (OMP-TFSI) was the main scope of this study. Boron doped diamond (BDD) and Au electrodes on quartz resonators were used as the substrates. A typical Pt deposition on BDD and Au was accomplished by applying short electrical pulses followed by relaxation phases for different duration in order to find optimal deposition conditions. In order to prove whether Pt was deposited on the electrode, samples were cycled in 0.1 M H2SO4 after deposition. In addition to electrochemical parameters, in the experiments on Au, the electrochemical quartz crystal microbalance permitted to monitor directly changes in the resonance frequency and damping associated with the Pt ion reduction processes.

Low loaded platinum (Pt) based binary catalyst electrode for PEMFC by plasma co-sputtered deposition method

Pt_Ag alloy – catalysts are deposited on carbon paper (Pt_Ag/C) by plasma magnetron co – sputtering method. These Pt_Ag deposited carbon papers are used as electrodes in Proton Exchange Membrane Fuel Cell (PEMFC). Co – deposition of Pt and Ag leads to alloy phase formation. Conical nanostructures of the alloyed catalysts are grown on the substrates at optimized deposition conditions. Electrodes with catalyst loading in the range of 0.05–0.25 mg cm−2 are fabricated by varying the sputtering time. Cyclic voltammetry shows that the catalytic activity depends on the shape and size of the catalysts nanostructures. The effect of catalyst loading on cell performance is investigated in terms of polarization curves. The Membrane Electrode Assembly (MEA) prepared with total anode and cathode Pt catalyst loading of 0.12 mg cm−2 exhibits the best cell performance with maximum power density of 503.19 mW cm−2. While catalyst loading in this investigation is 10 times lower than standard electrode loading, the cell performance achieved is comparable to that of standard cells. The mass – specific power density of the best prepared MEA is found to be 8 times higher than the MEA with conventional Pt/C standard electrode with 2 mg cm−2 Pt loading.