Nitrate Bath Research Articles

Role of Morphology on Zinc Oxide Nanostructures for Efficient Photoelectrochemical Activity and Hydrogen Production.

Energy generation today heavily relies on the field of photocatalysis, with many conventional energy generation strategies now superseded by the conversion of solar energy into chemical or thermal energy for a variety of energy-related applications. Global warming has pointed to the urgent necessity of moving away from non-renewable energy sources, with a resulting emphasis on creating the best photocatalysts for effective solar conversion by investigating a variety of material systems and material combinations. The present study explores the influence of morphological changes on the photoelectrochemical activity of zinc oxide nanostructures by exploiting electrodeposition and capping agents to control the growth rates of different ZnO facets and obtain well-defined nanostructures and orientations. A zinc nitrate (Zn (NO3)2) bath was used to electrodeposit ZnO nanostructures on an indium tin oxide glass (ITO) substrate at 70 °C with an applied potential of -1.0 V. Ethylenediamine (EDA) or ammonium fluoride (NH4F) were added as capping agents to the zinc nitrate bath. Extensive evaluation and characterization of the photoelectrochemical (PEC) capabilities of the resulting morphology-controlled zinc oxide nanostructures confirmed that altering the ZnO morphology can have positive impacts on PEC properties.

The study on the corrosion resistance enhancement of cerium-based conversion coatings by adipic acid and phytic acid post-treatment

This study investigates cerium-based conversion coatings enhanced with phytic and adipic acid treatments to improve the corrosion protection of galvanized steel. Optimal coating parameters were identified, including 15 min immersion in a 5 g/L cerium nitrate bath at pH= 3.5. The two-bath phytic acid post-treatment delivered unprecedented corrosion resistance, with an impedance of 11761 Ω.cm2 that markedly exceeds existing literature values. Surface characterization reveals phytic acid forms a more compact, homogeneous coating layer compared to adipic acid. Pull-off tests confirm improved adhesion strength of an epoxy topcoat applied to the phytic acid modified conversion coating. The substantial performance gains quantify the considerable advance this optimized coating system represents for sustainable corrosion inhibition.

Surfactant‐Mediated Electrochemical Precipitation of ZnO Nanospheres for Adsorption of Eosin Yellow & Rhodamine B Dyes

AbstractA simple electrochemical technique was used to synthesise zinc oxide (ZO) nanospheres and their in‐situ modification by a two‐step route of electrochemical precipitation with subsequent calcination. The ZO sample has been employed as an adsorbent for the removal of toxic dyes from their solutions. The electrochemical precipitation of zinc hydroxide (ZH) was carried out in a zinc nitrate bath at ~pH 4. The optimised concentration of 40 g dm−3 is used for the synthesis of modified zinc oxide (MZO) in the presence of the surfactant TEAB. XRD analysis confirms the formation of the heterostructure ZO. The field‐emission scanning electron microscopy (FESEM) images support the formation of hierarchical nanostructures with interconnected nanospheres in the presence of surfactant TEAB, which was confirmed by a high‐resolution transmission electron microscopy (HRTEM) study. The porous nature of ZO and MZO was established by the N2 adsorption‐desorption studies. The MZO sample showed ~99 % adsorption efficiency at an optimum dose of 0.09 g/20 mL of the 100 mg dm−3 Eosin Yellow dye solution within 120 min. However, the same sample showed 96 % adsorption efficiency at an optimum dose of 0.05 g/20 mL of the 100 mg dm−3 Rhodamine‐B dye solution within 120 min.

Corrosion and in vitro characteristics of cerium phosphate based chemical conversion coating on AZ31 magnesium alloy

A two-stage chemical conversion coating procedure was proposed for cerium phosphate based coating on Mg alloys. Initially, a layer of magnesium phosphate was obtained and the cerium phosphate based coatings were achieved by immersing the precoated sample in a cerium nitrate solution prepared in either water or ethanol. The resultant coating obtained from water based nitrate bath consisted of oxides and hydroxides of cerium in addition to cerium phosphate. On the other hand, due to the lack of OH– ions in ethanol based nitrate bath, oxides and hydroxides were suppressed and cerium phosphate rich coating was obtained. Scratch test and scanning vibrating electrode analysis confirmed the self-healing characteristics of the water based coating due to the presence of cerium oxide and hydroxide in the coating. The detailed corrosion studies revealed that the ethanol based coating exhibited superior corrosion resistance in both 1 wt% NaCl as well as in simulated body fluid due to the high stability of cerium phosphate in both test conditions. Both the coatings displayed acceptable cell viability (MG63 cell line) under physiological conditions and hence have the potential for both engineering and biomedical applications.

Novel ion-exchangeable nepheline glass-ceramics for dental application

Ion exchange of a glass-ceramic system with a specific crystalline phase can lead to materials with superior chemical, physical and mechanical properties. The aim of this study is to characterize newly synthesised nepheline glass-ceramics for dental restorative applications. Four novel experimental glasses based on the nepheline composition were ground into fine powders and then sinter-crystallized into monolithic glass-ceramics. The developed glass-ceramics were characterized before and after ion exchange in a potassium nitrate bath using X-ray diffraction, EDX-SEM, and biaxial flexural strength, hardness and solubility testing in accordance with ISO-6872. The ion exchange process of nepheline containing glass-ceramic Al20 increased the characteristic strength by more than 163% compared to the starting value. The experimental glass-ceramics increased in strength after ion exchange compared to their as-sintered values by 139%, 24% and 123%. The strength scatter decreased after ion exchange for the nepheline-containing glass-ceramics by 10%. The characterised glass-ceramics in this work require further investigation and have the potential to be developed into layered glass powders, which can be ion exchanged after sinter-crystallization to produce dental restorations with superior mechanical and chemical properties.

Influence of Zinc Oxide Nanostructure Morphology on its Photocatalytic Properties

Background: Zinc oxide (ZnO) is a transparent oxide material with a theoretical bandgap of 3.4 eV, which finds potential applications, including transistors, varistors, solar cells, and other solar applications. The properties of ZnO can be manipulated by controlling its morphology. Methods: The orientation and well-defined nanostructures can be obtained by controlling the growth rates of various ZnO facets by utilizing appropriate capping agents. Here, we report the electrodeposition of ZnO nanostructured thin films in the presence of various capping agents to obtain different ZnO morphologies. The electrodeposition of ZnO nanostructures was carried out on an indium doped tin oxide (ITO) with a glass substrate by using a zinc nitrate (Zn (NO3)2) bath at 70 °C and an applied potential of -1.0 V. To this zinc nitrate bath, capping agents like ammonium fluoride (NH4F) or ethylenediamine (EDA) were added to obtain different ZnO morphologies. These various ZnO morphologies were characterized by scanning electron microscopy. Results: The composition of the nanostructures was analyzed by X-ray diffraction. The photoelectrochemical (PEC) properties of these ZnO nanostructures were measured using a PEC cell. Conclusion: The PEC properties were influenced by different ZnO morphologies.

The effect of bioactive glass nanoparticles on corrosion barrier performance and bioactivity of zinc oxide coatings electrodeposited on Ti6Al4V substrate

Zinc oxide coatings were electrodeposited on Ti6Al4V substrates from a nitrate bath with and without 1 wt% BG nanoparticles at −1.2 and −1.4 VAg/AgCl, where the former voltage created a spherical morphology, the latter developed a flower-like one. The spherical morphology was modified through the incorporation of BG nanoparticles, where surface roughness, wettability, and adhesion strength of the coating were enhanced. The coatings with spherical morphology also revealed complete barrier property after immersion in PBS solution. However, fully adverse effects were found for the coatings deposited at −1.4 VAg/AgCl. This indicates that morphology is the most important factor determining the properties of ZnO and ZnO-BG coatings. The highest corrosion barrier performance was achieved for the ZnO-BG composite coating with spherical morphology. Although the composite coating with flower-like morphology did not provide complete barrier property at short immersion times, it earned that at longer times due to the plugging supported by the BG nanoparticles. The bioactivity tests in SBF at long times showed that the formation of Ca-P deposits on the surface of the composite coatings was noticeably improved.

Pulse-reverse electrodeposition of a conversion coating based on zinc cation and 3-nitrobenzoic acid on carbon steel to enhance adhesion and protective function of epoxy coating

This work introduces a pulse-reverse electrodeposition method for the application of conversion coating on carbon steel from 0.1 M 3-nitrobenzoic acid and 0.1 M zinc nitrate bath. The impact of current density changes on the surface morphology, composition, and electrochemical characteristics of conversion coatings was explored by surface analysis methods, contact angle, and electrochemical measurements. Results depicted the highest anti-corrosion performance for the sample treated by 0.045 A/cm2. Afterward, an epoxy coating was fabricated over the treated samples. The effect of conversion coating on the epoxy electrochemical behavior and adhesion properties was studied. According to the findings, the adhesion strength and anticorrosion performance of epoxy coating enhanced after the substrate carbon steel being modified by the conversion coating.

Electrochemical Deposition of ZnO Nanowires on CVD-Graphene/Copper Substrates.

ZnO nanostructures were electrochemically synthesized on Cu and on chemical vapor deposited (CVD)-graphene/Cu electrodes. The deposition was performed at different electrode potentials ranging from −0.8 to −1.2 V, employing a zinc nitrate bath, and using voltametric and chronoamperometric techniques. The effects of the electrode nature and of the working electrode potential on the structural, morphological, and optical properties of the ZnO structures were investigated. It was found that all the samples crystallize in hexagonal wurtzite structure with a preferential orientation along the c-axis. Scanning electron microscopy (SEM) images confirm that the presence of a graphene covered electrode led to the formation of ZnO nanowires with a smaller diameter compared with the deposition directly on copper surface. The photoluminescence (PL) measurements revealed that the ZnO nanowires grown on graphene/Cu exhibit stronger emission compared to the nanowires grown on Cu. The obtained results add another possibility of tailoring the properties of such nanostructured films according to the specific functionality required.

Spectroelectrochemistry and photoelectrochemistry of electrodeposited ZnO nanorods

AbstractThe electrodeposition of nanostructured semiconductors with tunable properties is of vital importance to develop optoelectronic devices. In this work, we introduce a novel synthesis protocol involving a multiple pulse electrodeposition nucleation stage combined with conventional potentiostatic ZnO nanorod growth in a nitrate bath. The in‐situ nucleation step allowed a higher surface density of ZnO nanorods. The effect of potential and total charge transferred during the nanorod growth was also systematically studied. Besides, spectroelectrochemical properties of different diameter electrodeposited ZnO nanorods were compared. Electrochemical Burstein‐Moss shift was observed for the different diameter ZnO nanorods when the potential was modified. Finally, spectroelectrochemical measurements of small diameter (≈60 nm) ZnO nanorods were carried out under different conditions, for example, electrolyte composition and amount of dissolved O2, to establish how these parameters affect the Burstein‐Moss shift.

Electrodeposition and structural characterization of MCrO3 (M = La, Pr, Nd, Gd, Dy and Y) perovskite oxide coatings on stainless steel substrates

One of the significant challenges of the effective use of functional oxide materials in device applications is to obtain them in the form of thin films or thick coatings. In this work, we show cathodic electrodeposition technique as a cost effective method for fabrication of perovskite chromite coatings. Amorphous precursor hydroxide coatings of M (M = La, Pr, Nd, Gd, Dy, Y) and Cr were co-deposited on stainless steel electrode by cathodic electrodeposition from a nitrate bath. These precursor coatings were further heat treated to obtain MCrO3 perovskite oxide coatings. Heat treatment of La–Cr hydroxide precursor coatings at 600 °C and 800 °C resulted in coatings of La2CrO6 and LaCrO3 phases respectively. The other M−Cr hydroxides on heating at 800 °C for 2 h formed respective single phase MCrO3 perovskite coatings. Interestingly, the SEM images of heat treated perovskite coatings show different morphologies with varying M in MCrO3 (M = La, Pr, Nd, Gd, Dy and Y).

Quantification of the chemical reactivity of molten nitrate salts with heat treatable aluminum alloys

This work explores the conditions for safe heat treatment of aluminum alloys containing lithium and magnesium in molten sodium nitrate (NaNO3) bath furnaces, and conditions where industrial accidents may occur. Using calorimetry coupled to classical thermodynamics, the strength of classical thermodynamics when analyzing thermal curves was demonstrated through a series of small-scale thermal analyses of various aluminum alloys in contact with sodium nitrate. This system was selected to illustrate reactions that may lead to severe and violent heat effect phenomena. Using idealized binary alloys, severe oxidation of magnesium- and lithium-rich aluminum alloy samples were shown to occur near 500 °C, a temperature range dangerously close to the operating temperature of solution heat treatment furnaces in manufacturing processes of heat treatable aluminum alloy sheets used in the aerospace industry. Commercial aluminum alloys AW257, 2198, 2024, and 1050 were also assessed with the same tools. The temperature that needed to be reached for these commercial aluminum alloys to react with molten sodium nitrate was significantly higher than the normal operating temperature of a conventional solution heat treatment furnace.

Electrochemical aspects of zinc oxide electrodeposition on Ti6Al4V alloy

Zinc oxide has become one of the most popular metal oxides in biological applications, however, the development of an efficient coating process remains a challenge since control of deposition parameters plays a significant role. In this study, electrodeposition of zinc oxide from zinc nitrate bath on Ti6Al4V substrate has been studied. The effect of substrate surface preparation, applied potential, and bath temperature on surface morphology and grain orientation of deposits were evaluated. Various morphologies including spherical, worm-like, nanoflakes, and flower-like were obtained by changing the potential and temperature. Unlike the surface preparation of the substrate, the temperature and potential had a significant effect on the grain orientation of the coatings; grain orientation of deposits changed from polygonal to basal by increasing temperature and potential. According to electrochemical analysis, at lower temperatures, the initial nucleation and growth of zinc oxide occur through the formation of zinc hydroxide precursor. In contrast, the zinc oxide directly nucleates at higher temperatures without formation of intermediate zinc hydroxide. Because of this different electrodeposition mechanism, a preferred (10.0) grain orientation was obtained at lower temperatures, while (00.2) grain orientation was intensified at high temperatures.

Role of Additives in Electrochemical Deposition of Ternary Metal Oxide Microspheres for Supercapacitor Applications.

A simple two-step approach has been employed to synthesize a cobalt–nickel–copper ternary metal oxide, involving electrochemical precipitation/deposition followed by calcination. The ternary metal hydroxide gets precipitated/deposited from a nitrate bath at the cathode in the catholyte chamber of a two-compartment diaphragm cell at room temperature having a pH ≈ 3. The microstructure of the ternary hydroxides was modified in situ by two different surfactants such as cetyltrimethylammonium bromide and dodecyltrimethylammonium bromide in the bath aiming for enhanced storage performance in the electrochemical devices. The effect of the surfactant produces a transition from microspheres to nanosheets, and the effect of micelle concentration produces nanospheres at a higher ion concentration. The ternary hydroxides were calcined at 300 °C to obtain the desired ternary mixed oxide materials as the electrode for hybrid supercapacitors. X-ray diffraction analysis confirmed the formation of the ternary metal oxide product. The scanning electron microscopy images associated with energy-dispersive analysis suggest the formation of a nanostructured porous composite. Ternary metal oxide in the absence and presence of a surfactant served as the cathode and activated carbon served as the anode for supercapacitor application. DTAB-added metal oxide showed 95.1% capacitance retention after 1000 cycles, achieving 188 F/g at a current density of 0.1 A/g, and thereafter stable until 5000 cycles, inferring that more transition metals in the oxide along with suitable surfactants at an appropriate micellar concentration may be better for redox reactions and achieving higher electrical conductivity and smaller charge transfer resistance. The role of various metal cations and surfactants as additives in the electrolytic bath has been discussed.

Electrodeposition of Ag-Pd Alloy at Ru Substrate from Simple Acidic Nitrate Bath

Ag-Pd films were electrodeposited on Ru substrate from acidic nitrate electrolytes with various metal ion concentration ratios. The electrolytes were stable for about 5 days. The alloy composition exhibits an increase in Pd fraction with higher overvoltage, covering a composition range between 3 and 80 at% by using 3 different baths. Electrodeposition from the Ag-rich electrolyte resulted in 3%at,Pd faceted particles with size 5–30 μm. The Pd-rich electrolyte in contrast shows the formation of μm-size particles, the size of which decreases with increasing overpotential. These films tend to delaminate, due to the limited adhesion provided by the Ru substrate and the internal stresses generated by the growth process. We also demonstrate precise targeting of alloy composition by growing equiatomic films, based on a procedure involving evaluation of the mass-transfer coefficient ratio of the elements involved. Crystal structure shows several solid solutions consisting of Pd-rich and Ag-rich, and the composition distribution at the microscale is probably generated by the complex surface diffusion. Electrodeposition was also conducted with reduced Ru substrate, showing the significant impact of the initial stage on the lateral growth of AgPd films.

Marine corrosion resistance of CeO2/Mg(OH)2 mixed coating on a low alloyed steel

Mixed Mg(OH)2/CeO2 coatings were deposited by cathodic electrodeposition on AISI 4135 steel in order to improve its resistance to marine corrosion. CeO2 coating was first prepared by cathodic electrodeposition in a low concentration of cerium nitrate bath. Then, brucite layer is formed by cathodic polarisation in magnesium nitrate bath. Scanning electronic microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and micro-Raman spectroscopy (μ-Raman) analysis were used to study the morphology, chemical composition, microstructure and thickness of the coatings. The corrosion resistance of the coatings was evaluated in artificial seawater by electrochemical methods. CeO2 coating presents a porous and cracked structure; consequently, it offers low corrosion protection of steel in seawater. However, Mg(OH)2/CeO2 mixed coatings have a more uniform and compact structure and present a better corrosion protection of steel in seawater. The protection efficiency of these coatings is then discussed and a protection mechanism is proposed after surface and cross-section SEM and μ-Raman analyses of the coating after several seawater immersion durations.

Investigation on the corrosion behavior of lanthanum phosphate coatings on AZ31 Mg alloy obtained through chemical conversion technique

A lanthanum based phosphate coating on magnesium AZ31 alloy was prepared through chemical conversion coating technique and characterized their corrosion performance. The coating was obtained in a two stage procedure using two different solvents, water or ethanol for preparing the coating nitrate bath. The chemical compositions and structures were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Corrosion performance of the developed coatings in 3.5 wt% NaCl was evaluated using electrochemical polarization and immersion tests. The results indicated that lanthanum hydroxide formation rather than lanthanum phosphate was predominant in the coating prepared using water as solvent for the nitrate bath whereas using ethanol as solvent produced lanthanum phosphate rich and defect less coating. An excellent corrosion resistance (in immersion test) was noticed with coatings prepared using ethanol as solvent (0.046 mm/y) over the bare sample (1.30 mm/y) as well as samples coated using water as solvent (0.278 mm/y).

Phase Separation in Electrodeposited Ag-Pd Alloy Films from Acidic Nitrate Bath

The electrochemical deposition of Ag-Pd from acidic nitrate solutions has been studied. Under suitable conditions, phase separation in the form of solid solutions with different compositions is observed at the micron scale. The phase separation is not generated by electrochemical instabilities, but instead is due to a wide difference in the intrinsic reduction kinetics and the distinct nucleation characteristics. At UPD conditions Ag-Pd films could be grown via underpotential codeposition, in close agreement to thermodynamic predictions. At intermediate overpotentials, phase separation occurs due to local concentration gradients generated by mass transfer limitation for Ag and large nucleation barrier for Pd. Under mass transfer limitations, the growth is uniform and the composition corresponds to the prediction based on the ion diffusivities.

Electrocatalytic and pseudocapacitive properties of cobalt (hydro)oxide films on sintered metal fiber filter

Cobalt (hydro)oxide films on Bekipor ST 20AL3 sintered metal fiber were formed by electrochemical deposition under galvanostatic conditions using different electrolyte baths (nitrate, acetate and chloride). Cobalt oxide films were prepared via thermal treatment of as-deposited specimens at 673 K. Electroactive surface area of as-deposited and annealed films was estimated using oxidation–reduction system containing ferricyanide/ferrocyanide. Electrocatalytic and pseudocapacitive properties of the prepared films were investigated using 0.1 M NaOH aqueous solutions. The maximum specific capacitance of 1324 F g−1 was observed for α-Co(OH)2 films electrodeposited from nitrate-containing electrolyte. Similarly, the highest electrocatalytic activity and stability in oxygen evolution reaction (OER) was determined to be characteristic for Co3O4 films derived from nitrate bath.

The electrochemical oxidation of salicylic acid and its derivatives on modified PbO<sub>2</sub>-electrodes

The results of the study of electrochemical oxidation of salicylic acid on PbO2-based anodes for effective wastewater treatment from organic pollutants have been summarized. Both the influence of various factors on the decomposition rate of organic substances and the influence of various modifying additives of lead dioxide anode on the process of mineralization of salicylic acid have been established. The total probable sequence of reactions to salicylic acid mineralization has been proposed. It is established that the destruction of salicylic acid in the first stage occurs through the accumulation of aromatic hydroxylation products, and during the total destruction - the destruction of the aromatic system with the formation of aliphatic compounds takes place. It is shown that the use of PbO2, deposited from methanesulfonate electrolytes and modified electrodes significantly reduces the conversion time of salicylic acid in aliphatic products compared to lead dioxide anodes obtained by traditional technology from nitrate bath. The highest degradation rate occurs at the anodes modified by bismuth. It was found that the destruction of the 5-aminosalicylic acid occurs through an intermediate oxidation of amino-group to hydroxy.