Spray Deposition Technique Research Articles

Mechanical and microstructural analysis of a AlSi-ZrO2 metal matrix composite using optimized artificial neural network and experimental data

Spray deposition methods has emerged as an alternative to powder metallurgy and ingot routes. This research aims to study the effect of flight distance as a potential key factor that changes the optimum percentage of aluminium silicon- zirconium oxide in terms of mechanical and microstructural properties. The alloy is sprayed at varying the flight distance from 320 mm to 480 mm. The composite were prepared by spray deposition technique and effects on microstructural properties were examined. The aluminium silicon- zirconium oxide composite was subjected to hot isostatic pressing for reducing the porosity of the deposit from 14.4% to 8.2%. A series of experimental study were carried out in the laboratory by varying the flight distance from 320 mm to 480 mm for aluminium silicon- zirconium oxide composite to characteristic loading. In this paper, an optimized artificial neural network using genetic algorithm are developed to predict the mechanical behaviour for aluminium silicon- zirconium oxide composites. Based on the experimental data, the ANN models were developed, trained and tested. The microstructure of the AlSi-ZrO2 composite consisted of finely divided globular shaped eutectic Si uniformly distributed in the Al matrix. With addition of zirconium oxide composition to AlSi alloy, the tensile strength and micro hardness increased from 123 MPa to 147 MPa and, 48 HV to 72 HV, respectively. The preferred flight distance for the current study is found to be 420 mm. Microstructural images obtained at flight distance consist of co-existing primary Si phase and needle like eutectic Si. The physical properties, such as tensile strength, compressive strength, yield strength, micro hardness and porosity of sprayed aluminium silicon- zirconium oxide can hence be adjusted by setting the optimized flight distance. The developed ANN-GA method proved to be accurate, reduced time and efficient to predict the numerous samples and it will help materials designers to design their future experiments effectively.

Tailoring Thermal Transport Properties by Inducing Surface Oxidation Reactions in Bulk Metal Composites.

Surface modification is used to dramatically alter the thermal properties of a bulk metallic material. Thermal barrier coatings (TBCs) are typically applied using spray deposition or laser-based techniques to create a ceramic coating on a metal substrate. In this study, an effective TBC is created directly on a metallic substrate by inducing surface chemical reactions. Aluminum-zirconium (Al-Zr) substrates are used to induce surface-limited reactions that produce a 75-80% decrease in bulk thermal conductivity and diffusivity, respectively. The substrates are cylindrical disks 12.6 mm diameter and 2 mm thickness. Thermal properties are measured using laser flash analysis (LFA) at incrementally elevated temperatures. Focused ion beam (FIB) slicing of the substrate coupled with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) show that the substrate oxidized only along the outer 20 μm of the bulk surface. The layer thickness is significantly less than typical TBCs that can range from 50 to 300 μm yet the 20 μm coating still achieves a dramatic reduction in thermal transport properties. Additionally, thermal analysis reveals a sequence of exothermic reactions starting at 439 °C that include both intermetallic (i.e., ZrAl3) and oxidation (i.e., Al2O3 and ZrO) reactions suggesting continuous surface bonding at the coating-metal interface. The onset of exothermic activity coincides with the transition in thermal properties measured using LFA. These results show that surface oxidation reactions could be used to dramatically alter the thermal transport properties of a metal substrate.

Stretchable MXene/Thermoplastic Polyurethanes based Strain Sensor Fabricated Using a Combined Electrospinning and Electrostatic Spray Deposition Technique

In this work, a novel flexible electrically resistive-type MXene/Thermoplastic polyurethanes(TPU) based strain sensors was developed by a composite process of electrospinning (ES) and electrostatic spray deposition (ESD). Compared with other deposition processes, the sensing layer prepared by ESD has better adhesion to the ES TPU nanofiber membrane and is not easy to crack during the stretching process, thereby greatly improving the working range of the strain sensor. Furthermore, we obtained the sandwich structure easily by ES on the surface of the sensing layer again. This will help make the stress distribution more uniform during the stretching process and further increase the strain sensing range. The ESD-ES strain sensors were attached on skin to monitor various human motions. The results demonstrate that our ESD-ES strain sensors have wide application prospects in smart wearable device.

Aerosol Spray Deposition of Liquid Metal and Elastomer Coatings for Rapid Processing of Stretchable Electronics.

We report a spray deposition technique for patterning liquid metal alloys to form stretchable conductors, which can then be encapsulated in silicone elastomers via the same spraying procedure. While spraying has been used previously to deposit many materials, including liquid metals, this work focuses on quantifying the spraying process and combining it with silicones. Spraying generates liquid metal microparticles (~5 μm diameter) that pass through openings in a stencil to produce traces with high resolution (~300 µm resolution using stencils from a craft cutter) on a substrate. The spraying produces sufficient kinetic energy (~14 m/s) to distort the particles on impact, which allows them to merge together. This merging process depends on both particle size and velocity. Particles of similar size do not merge when cast as a film. Likewise, smaller particles (<1 µm) moving at the same speed do not rupture on impact either, though calculations suggest that such particles could rupture at higher velocities. The liquid metal features can be encased by spraying uncured silicone elastomer from a volatile solvent to form a conformal coating that does not disrupt the liquid metal features during spraying. Alternating layers of liquid metal and elastomer may be patterned sequentially to build multilayer devices, such as soft and stretchable sensors.

Study of kesterite Cu2ZnSnS4 (CZTS) thin films deposited by spray technique for photovoltaic applications

For the synthesis of an absorber crystalline layer of the solar cell device, the Cu2ZnSnS4 (CZTS) absorber is fabricated by using the sol–gel method and the spray deposition technique. The proposed method in this study aims to synthesize stoichiometric CZTS thin films without the sulfurization process and use of a toxic atmosphere. Thin films CZTS were sprayed on the substrates annealed at different temperatures, that are 250, 300 and 350 °C, for solar cell applications. This study highlights the effect of the substrate temperature on the structural, morphological and optical properties of the CZTS deposited films. Therefore, in this study, at the higher substrate temperature, which is 350°C, a semi-optimal band-gap value of E g = 1.3 eV was obtained. For the all prepared CZTS thin films, the structural and optical properties were discussed in the light of the variations in the observed microstructure at different substrate temperatures.

Investigation of optimum process parameter of lost foam casting of A356/SiC metal matrix composite

Metal Matrix Composites (MMCs) are unceasingly substituting engineering materials because of its high stiffness and strength over homogeneous materials formulation. It has been utilized in engineering structural applications like aerospace, automotive and defense. In industries MMCs are mostly fabricated by squeeze casting, stir casting, infiltration technique, and spray deposition technique. In these processes, there are some limitations like difficulties in producing intricate shapes, homogeneous distribution of ceramic particles and poor wetting property between reinforcement and matrix alloy etc. To overcome these limitations, Lost Foam Casting (LFC) is used to fabricate MMCs. In this investigation an attempt has been made to produce intricate castings of (A356 Al alloy-SiC) particulate type Metal Matrix Composites using LFC process. The rectangular expanded polystyrene (EPS) patterns are used in this LFC process instead of circular patterns. The LFC process quality is strongly affected by the elimination of degradation product which in turn depends on the process parameters such as sand grain size, coating grain size, pouring temperature and coating method. These four process parameters with three levels are considered for Taguchi’s technique with L9 Orthogonal Array (OA) and the experiments were conducted. Density and tensile strength of the castings are considered as quality characteristics of the LFC process. From the ANOVA results, it reveals that the sand grain size and coating grain size mainly influence the casting quality. The optimal process parameters are sand grain size of AFS 50, coating grain size of 212 µm, pouring temperature 800 °C and coating method of brushing technique.

Effect of Annealing Temperature on Properties of Tin Oxide Films Prepared by Electrostatic Deposition Technique

Abstract In this work, tin oxide films were prepared by electrostatic spray deposition technique. The effect of post annealing temperature on properties of prepare film was performed. The structural, surface morphology and optical properties of tin oxide films were characterized by X-ray diffraction, field-emission scanning electron microscope, and UV-Visible spectrophotometer. The crystalline size is found to increase with increase the annealing temperature. Moreover, the effect of annealing temperature on physical properties of tin oxide films has been performed

Properties of Manganese Oxide Films Prepared by Electrostatic Deposition Technique

Abstract In this work, the electrostatic spray deposition technique was applied to prepare manganese oxide tin films. The effects of post annealing at various temperatures on the properties of manganese oxide film were studied. The properties of the films were assessed by X-ray photoelectron spectroscopy and field-emission scanning electron microscope. In addition, the electrochemical properties of the manganese oxide films were investigated. It was found that the prepared films could be used for super-capacitive, energy storage devices

Tetrahydro-dibenzo[a,d] Annulene-5, 11-Dihydrazone and Magnesium Oxide Used to Control the Corrosion of Aluminium in Chloride Ions Environment

Chloride ions interact with aluminium in marine atmosphere to form corrosion cell. Due to this corrosion reaction occurs on their surface, aluminium is oxidized into Al3+. The corrosion reaction accelerates deterioration in metal and it produces galvanic, pitting, stress, crevice, intergranular corrosion. Chloride ions decrease internal and external strength of aluminium metal. It is a very important metal so used in different appliances for e.g. road, water, air transports, housing, railways and other fields. Nanocoating and electrospray techniques used to check the corrosion of aluminium metal. For nanocoating and electrospray materials applied tetrahydro-dibenzo[a,d] [7] annulene-5, 11-dihydrazone and MgO. Both materials formed composite barrier and developed a passive surface for Cl- ions. This barrier reduced the corrosion rate of aluminium. Nozzle spray and chemical vapour deposition technique used for coating process. The corrosion rate of metal was determined by gravimetric method. Corrosion potential and current density were calculated by potentiostat. The composite barrier formation was confirmed by activation energy, heat of adsorption, free energy, enthalpy and entropy. These thermal parameters were obtained by Arrhenius equation, Langmuir isotherm and Transition state equation. The adsorption of tetrahydro-dibenzo[a,d] [7] annulene-5,11-dihydrazone and MgO electrospray on aluminium surface was depicted by Langmuir, Frundlich and Temkin isotherm. The results of surface coverage area and coating efficiency were noticed that both materials were mitigated the corrosion rate of aluminium in chloride ions environment

Flash light sintered SDC cathodic interlayer for enhanced oxygen reduction reaction in LT-SOFCs

To commercialize solid oxide fuel cells, many methods for reducing the production time of manufacturing a fuel cell membrane-electrode-assembly (MEA) using a non-vacuum process have been studied and still the post-heat treatment process is an issue. This paper discusses an alternative sintering method to replace the conventional thermal sintering step for ceramic thin film fabrication, which is time consuming and costly. We fabricated samarium-doped ceria (SDC) thin films, which has high ionic conductivity and high surface exchange coefficient for oxygen reactions at the cathode side. The films were deposited by chemical solution deposition (CSD) method utilizing electrostatic spray deposition (ESD) technique. Thermal decomposition and crystallization steps are required as a post-heat treatment process to obtain desired material properties. For this purpose, the flash light sintering method is adopted and compared with the conventional thermal sintering process using halogen furnace. With this flash light sintering method, the conventional post-heat treatment process time can be significantly reduced from tens of hours to a few seconds. Scanning electron microscopy, X-ray diffraction, and transmission electron microscopy analyses were carried out for material characterizations. Additionally, electrochemical impedance analysis and current-voltage behavior measurements were conducted. By successful fabrication of SDC cathodic functional layer utilizing flash light irradiation process, the 2-folds of fuel cell performance enhancement was obtained in terms of the peak power density at the measurement temperature of 450 °C.

Annealing Effect on the Properties of Electrochromic V2O5 Thin Films Grown by Spray Deposition Technique

Nanostructured electrochromic V2O5 thin films were prepared using spray pyrolysis technique growth at a temperature of 250 °C using air-carrier spray deposition, starting from ammonium metavanadate precursor in water, followed by annealing at 400 °C in O2 atmosphere for 2 h. The V2O5 films were characterized by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy, and their electrochromic behavior was studied using optical spectroscopy and cyclic voltammetry in both the as-deposited and postannealing case. The studies showed that the simple, cost -effective, suitable for large area deposition method used can lead to an interesting surface structuring with large active surface properties suitable for electrochromic applications. Further studies for growth optimization and improvements of films properties and stability are to be performed.

Synthesis and Characterization of (Co,Ni)O Solid Solutions As Protective Coatings for Inert Anodes in Aluminum Electrolysis

The industrial production of primary aluminum from alumina ore (Al2O3) is still carried out by the Hall-Héroult process. The process relies on dissolving alumina in an electrolyte consisting mainly of liquid Na3AlF6 at 950-1000 °C. While the reduction of dissolved Al3+ ions in aluminum occurs at the cathode, the complementary reaction occurs at a carbon anode that is consumed to form carbon dioxide, which necessitates its regular replacement (every 25 days). The overall reaction is the following:Canadian aluminum smelters produce annually about 6 Mt of CO2 eq(reported in 2017), which is equivalent to the CO2 amount generated annually by about 2 million cars.The substitution of consumable carbon anodes with inert (O2-evolving) anodes in the electrochemical cells to produce aluminium would have significant environmental benefits because it would eliminate the emissions of carbon dioxide and perfluorocarbons associated with the consumption of the carbon anode. However, the design of inert anodes is a major challenge because of the severe Al electrolysis conditions (cryolithic medium at 960 °C), which requires materials with excellent resistance to corrosion and thermal shock as well as adequate electrochemical properties [1].Single phase Cu65Ni20Fe15 alloy is a promising inert anode for Al production due to its ability to form a protective NiFe2O4 layer upon Al electrolysis. However, its corrosion resistance is still insufficient and a protective layer is required to prevent the penetration of electrolyte into the nickel ferrite layer and the formation of fluorides during Al electrolysis [2-4].In this context, the use of (Co,Ni)O-based protective coatings for metallic anode appears promising [5]. However, it is challenging to prepare a single phase, coherent and crack-free oxide layer as required for industrial Al production. A potentially relevant method to produce (Co,Ni)O coated inert anodes is by direct deposition of (Co,Ni)O oxide compounds by spray deposition techniques such as suspension plasma spray (SPS) and high velocity oxygen fuel (HVOF). These additive manufacturing deposition are well-established technologies for producing protective oxide coatings for various industrial applications (e.g. gas turbines).As a first step toward this goal, pure CoxNi1−xO solid solutions have been prepared over the whole composition range by a two-step procedure that consisted of high-energy ball milling followed by a heat treatment of Co3O4 and NiO powders [6]. Then, the thermal stability and electrical conductivity of (Co,Ni)O solid solutions were determined at temperatures ranging between 700 and 1000 °C. Also, their dissolution rate was measured in K-based cryolite at 700 °C and in Na-based cryolite at 1000 °C.In a second step, (Co,Ni)O powders have been used as raw materials for the thermal spraying (HVOF and SPS) of protective coatings onto Cu-Ni-Fe inert anodes [7]. The morphological and microstructural characteristics of the coating depending on the thermal spray conditions will be presented. The oxidation behaviour of the coated inert anodes under air and argon is presented. Preliminary investigation of the electrochemical behaviour under Al electrolysis conditions of the (Co,Ni)O/Cu-Ni-Fe anodes will be also presented and discussed.

Design of advanced one-step hydroxyapatite coatings for biomedical applications using the electrostatic spray deposition

Calcium phosphate ceramics (CaP), particularly hydroxyapatite Ca10(PO4)6(OH)2 (HAP), are widely used as surface coatings on top of titanium and its alloys in biomedical applications thanks to their ability to form strong bonds with natural bone tissues. In this paper, the electrostatic spray deposition technique (ESD) by using an organic phosphorus (V) precursor is proposed as an alternative to the widely used plasma-spraying process. This bottom-up approach enables the one-step fabrication of single-phase crystalline HAP coatings with unique morphologies. The microstructure and composition of the deposited CaP layers result from a delicate compromise between the physicochemical properties of the precursor solution and the ESD deposition conditions. An in-depth study of their structural, microstructural, compositional properties and their reactivity with Ti6Al4V is undertaken. It shows that the Ca/P molar ratio and the nature of phases are strongly dependent on hydrolysis and evaporation of the P(V) precursor in the ESD process. Optimized deposition conditions are found by using solvents of low-boiling point, for which the coatings deposited above 325 °C correspond to a well crystalline, nanostructured, and single-phase HAP. Infrared heat treatment of a coating prepared from the one optimized precursor solution promotes nanostructured HAP.

WO3/TiO2 hierarchical nanostructures for electrochromic applications

In the present work, we report the low temperature preparation of WO3/TiO2 films via a two step process by combining chemical bath deposition and nebulized spray deposition techniques. We investigate the influence of WO3 layer on the structural, compositional, morphological and electrochemical properties of TiO2 films. The deposition of WO3 nanoplates on the TiO2 layer effectively improves the current density of the TiO2 films. The electrochemical study of the annealed WO3/TiO2 films showed a colouration efficiency of 128.3 cm2 C−1, optical modulation (ΔT) of 78%, reversibility of 77.2% and with a fast response of 6 s for colouration and bleaching, and importantly, exhibited an excellent durability for 1000 cycles. This enhancement is ascribed to the interconnected nanoplate bundles which accommodate more charges, facilitate faster charge transport and in particular, the complementarity of the WO3–TiO2 layers, result in complement between each other, thus leading to efficient electrochromic performance.

Impact of heat drying on the physical and environmental characteristics of the nanocellulose-based films produced via spray deposition technique

Nanocellulose (NC) and NC-based composites have gained considerable attention in recent years due to their biodegradability and recyclability. Spray deposition has emerged as a potential technique to produce NC films due to the rapidity and simplicity of the process. The major hurdle regarding the efficient production of NC-based films is the drying process. The aim of the current study is to significantly reduce the drying time of NC films and consequently examine the impact of drying on their mechanical characteristics, barrier and environmental performance. The NC films produced by spray deposition were dried at 50 °C, 75 °C and 100 °C and their characteristics were compared with the films produced via the same method at ambient temperature (28 ± 2 °C). Heating the films in an oven up to 75 °C had a negligible effect on mechanical characteristics while slightly improving the barrier properties as compared with the ambient dried films. However, the dimensional stability was only achieved when the temperature was below 75 °C. Drying could be accomplished at the faster drying rate and the NC films found to have lower embodied energy in comparison with the conventional packaging materials.

Superhydrophobic PVC/SiO2 Coating for Self‐Cleaning Application

AbstractA lotus leaf like self‐cleaning superhydrophobic coating has high demand in industrial applications. Such coatings are prepared by alternative dip and spray deposition techniques. A layer of polyvinyl chloride is applied on glass substrate by dip coating and then spray coated a suspension of hydrophobic silica nanoparticles at substrate temperature of 50 °C. This coating procedure is repeated for three times to achieve rough surface morphology which exhibits a water contact angle of 169 ± 2° and sliding angle of 6°. The superhydrophobic state of the coating is still preserved when water volume of 1.2 L is used to impact the water drops on coating surface. The stability of the wetting state of the coating is analyzed against the water jet, adhesive tape and sandpaper abrasion tests. The prepared superhydrophobic coating strongly repelled the muddy water suggesting its importance in self‐cleaning applications.

Superhydrophobic Coating Using TiO2 NPs/PMHS Composite for Self‐Cleaning Application

AbstractIn the present research work, spray deposition technique is adopted for the fabrication of superhydrophobic coating on glass slide using TiO2 nanoparticles and polymethylhydrosyloxane (PMHS) composite. The prepared superhydrophobic coating revealed hierarchical surface morphology due to different micro and nanoscaled grains of TiO2 NPs/PMHS composite. The water drops hardly stay on the superhydrophobic coating and roll off the surface at sliding angle of 6° due to high water contact angle of 163 ± 2°. As a result, the prepared superhydrophobic coating revealed excellent self‐cleaning performance. To evaluate the mechanical durability the prepared superhydrophobic coating, the coating surface is exposed to water jet, water drop impact, adhesive tape peeling, and sandpaper abrasion tests. This coating approach can be applied to the substrates of any size and shape.

Synthesis and Characterization of Physical Properties of the NiO Thin Films by Various Concentrations

Abstract In this work, nickel oxide was deposited on a glass substrate at by spray deposition technique; the structural, optical and electrical properties were studied at different NiO concentrations (0.05, 0.10 and 0.15 mol.l−1). Polycrystalline NiO films with a cubic structure with a strong (111) preferred orientation were observed at all sprayed films with minimum crystallite size of 11.97 nm was attained of deposited film at 0.1 mol.l−1. However, α-Ni(OH)2 was observed at 0.15 mol.l−1. The NiO thin films have good transparency in the visible region, the band gap energy varies from 3.54 to 376 eV was affected by NiO concentration, it is shown that the NiO thin film prepared at 0.05 mol.l−1 has less disorder with few defects. The NiO film deposited at 0.15 mol.l−1 has the electrical conductivity was 0.169 (Ω.cm)−1.

High temperature erosion behaviour of Type AISI 446 stainless steel under the combined effect of surface modification and pre hot-corrosion

In the present study, the effect of Surface nano crystallization (SNC), using Ultrasonic shot peening (USP), on pre-hot corrosion-erosion behaviour of Type AISI 446SS at elevated temperatures is studied. No phase change was revealed by X-ray diffraction (XRD), however, the microhardness is significantly increased in the shot peened region for USPed samples. The USPed samples were subjected to low-temperature hot corrosion (LTHC) tests under isothermal conditions for 20 h at 550, 650 and 750 ℃. The LTHC tests were carried out by spray deposition techniques using two salt mixture (Na2SO4/NaCl). Alumina (Al2O3) sand operated air-jet erosion tester was used to test the pre-hot corroded samples. The passive layer formed during LTHC suffered expulsion of metallic flakes and led to a significant change in erosion rate.

Plasma Spray Deposition of HA-TiO2 on β-phase Ti-35Nb-7Ta-5Zr Alloy for Hip Stem: Characterization of Bio-mechanical Properties, Wettability, and Wear Resistance

In this work, a biomimetic coating of hydroxyapatite (HA)-and titania (TiO2) was deposited on low elastic β-phase Ti-35Nb-7Ta-5Zr (β-TNTZ) alloy by plasma spray deposition technique for orthopedic applications. The effect of TiO2 reinforcement on microstructure, mechanical properties, and bioactivity was investigated. The morphology, coating thickness, elemental composition, and phase composition of the developed coatings were characterized. The biomechanical behavior of the deposited coatings was investigated in terms of surface hardness, elastic modulus, and adhesion strength. It was found from the morphological investigation that the TiO2 reinforcement improves the microstructure and prevents the formation of defects in the coating. The biomimetic HA-TiO2 coated surface possessed pores, size ranging from 200 nm–600 nm that benefits the apatite growth and osseointegration. The EDS spectrum, mapping, and XRD analysis show that the deposited layer β-TCP, CaO, TTCP, TiO2 phases. The HA-TiO2 coating exhibits a very dense and thick layer of 100 µm–125 µm that exhibits excellent adhesion strength to offer mechanical interlocking to prevent delamination. The alloying of TiO2 improves the hardness from 1.67 GPa to 2.95 GPa that enhances the wear resistance. It was found that HA-TiO2 coating exhibits better hydrophilic and biocompatible surface as compared to HA-coating.