Nitric Acid Environment Research Articles

Electrochemical and theoretical evaluations of 3-(4-chlorophenyl)-7-methyl-5H-[1, 2, 4] triazolo [3,4-b][1,3,4]thiadiazin-6(7H)-one as corrosion inhibitor for copper in nitric acid environment

Electrochemical and theoretical evaluations of 3-(4-chlorophenyl)-7-methyl-5H-[1, 2, 4] triazolo [3,4-b][1,3,4]thiadiazin-6(7H)-one as corrosion inhibitor for copper in nitric acid environment

Exploring the impact of Al alloying on microstructure and hot nitric acid corrosion resistance of Ti-xAl (x=0, 1, 2, 3, 4, 5) alloys

Enhancing the corrosion resistance of titanium alloys in hot nitric acid environments is imperative for advancing spent fuel reprocessing. Here, we explored the impact of Al alloying on microstructure and corrosion resistance of Ti-Al alloys via experimental assessments and theoretical computations. Results indicated that Al alloying induced a comparable Widmanstatten structure and increased hardness. Electrochemical findings demonstrated the optimal corrosion resistance for the alloy with 4 wt% Al. DFT computation presented the highest WF and the lowest EF for Ti-4Al alloy, indicative of superior thermodynamic stability. Eventually, a mechanistic understanding of Al alloying on nitric acid corrosion resistance was proposed.

Electrolyte Effect on Photoetching of Gallium Nitride

The limited material removal rate of conventional chemical mechanical polishing (CMP) significantly hinders the fabrication efficiency and surface quality, thereby preventing the development of gallium nitride (GaN)-based devices. Moreover, the incorporation of photoelectrochemistry in CMP has garnered increasing attention because of its potential to enhance the quality and efficiency of the GaN process. However, a considerable gap still exists in the comprehensive understanding of the specific photoelectrochemical (PEC) behavior of GaN. Here, we report the influence of the electrolyte on the PEC etching of GaN. Various acids and bases were tested, with their pH being carefully adjusted. The concentrations of the cations and anions were also examined. The results showed that photocorrosion/photoetching was more pronounced in sulfuric acid, phosphoric acid, and nitric acid environments than in alkaline environments, but it was less pronounced in hydrochloric acid. Furthermore, the effects of pH and anion concentration on photoetching were investigated, and the results revealed that photoetching in acidic environments weakened with increasing pH levels and diminished with increasing sulfate concentration. The underlying reasons contributing to this observation were explored. These findings provide ideas for improving the photoetching efficiency of GaN, thereby enriching the photoelectrochemical mechanical polishing (PECMP) technology of GaN.

Recycling of SmCo Magnets by Removal of Iron via Oxidative Leaching

In the production of SmCo permanent magnets with excellent temperature stability, corrosion resistance, and oxidation resistance, samarium (Sm), one of the rare earth elements (REEs), and cobalt (Co) are employed. Cobalt (Co) is a crucial component in tool materials, nickel-based alloys, tablet and smartphone batteries, and electric car batteries. REEs and Co have been listed as critical raw materials by the European Union Commission for many years. Due to the ever-growing demand for Co and REEs in technological applications, the recovery of these elements from secondary sources has garnered significant interest. There are two types of SmCo magnets, one of which contains a high amount of iron, approximately 15.2%. This paper focuses on the recycling of Fe-bearing SmCo. In this study, an oxidative leaching process with nitric acid was developed to eliminate iron through in situ hydrolysis and to dissolve REEs and Co. The influence of experimental conditions on the formation of an amorphous iron compound through the hydrolysis of Fe3+ in a nitric acid environment was thoroughly examined based on a Taguchi orthogonal array. The optimal parameters for oxidative leaching were determined to be an acid concentration of 3 mol/L, a solid-to-liquid ratio of 1/10, and a process temperature of 60 °C.

Colloid-chemical properties of surfactant–nitric acid–water systems

The behavior of the surfactants Tween 80, SaS and alkyl betaine in aqueous and nitric acid environments as promising additives for nitrate leaching of hard-to-process ore concentrates of non-ferrous metals was studied. The influence of surfactant concentration (0.04–1.28 g/dm3), nitric acid concentration (0.1–10 g/dm3) and temperature (295–343 K) on the surface tension, critical micelle concentration (CMC), pH and optical density of aqueous surfactant solutions and surfactant–HNO3–H2O systems was found. The critical micelle concentration of the surfactants used was estimated. A positive effect of nitric acid on the surface activity of surfactants was discovered, which manifests itself in a decrease in both the CMC and the surface tension at the liquid–gas interface. The values of surface activity and Gibbs energy of surfactant micelle formation in aqueous and nitric acid media were calculated. Associative processes in the solutions and compositions were confirmed by measuring the optical density of the systems under study.

Electrochemical Behavior of an Alpha-Phase Titanium Alloy in Oxidizing Nitric Acid Environments: Influence of an Oxygen-Enriched Layer

The study focuses on establishing the influence of an oxygen-enriched layer (OEL) on the electrochemical properties of an alpha-phase titanium alloy, Ti-Al-Zr, in oxidizing nitric acid environments. Heat treatment was given to the material at 760°C for 700 h in air which resulted in the formation of an OEL on the surface. The electrochemical properties were studied and compared with as-received (AR) conditions by techniques like open-circuit potential (OCP), potentiodynamic polarization, chronoamperometry, and electrochemical impedance spectroscopy measurement. It was established that the presence of an OEL on the surface reduced the cathodic activity of oxidizing species on the material’s surface. The OCP value did not depend on the presence/absence of the OEL on the surface. The presence of the OEL on the surface promoted the formation of a protective passive film. The material with an OEL on the surface had a lower donor density as compared to the AR condition.

Study of the Thermodynamic Quantities of Adsorption and Activation of Piroxicam in Copper Corrosion in a Nitric Acid Environment

The objective of this work is to assess the inhibitory efficacy of the piroxicam molecule on copper corrosion in a 1M nitric acid medium using the mass loss technique (gravimetry). The inhibition efficiency, represented as IE (%), increases with higher concentrations and temperatures. Various adsorption isotherm models (Langmuir, El-Awady, Freundlich, and Temkin) were employed to describe the interactions between the molecule and metallic copper. The Dubinin-Radushkevich isotherm, along with the Adejo-Ekwenchi isotherm, was utilized to identify the types of adsorption. Additionally, the thermodynamic adsorption and activation functions were determined and analyzed.

The Growth Process and Photocatalytic Properties of h-MoO3 and α-MoO3 under Different Conditions

In this experiment, we investigated the effects of different reactions on the growth process and morphology of h-MoO3 and α-MoO3, and their optical properties and photocatalytic activities were also investigated. Orthogonal experiments were designed to investigate the effects of four influencing factors, namely the amount of ammonium molybdate tetrahydrate (AHM), the type of acid, the reaction temperature and the holding time, on the morphology of h-MoO3 by a microwave hydrothermal method. The phase and morphology were analyzed by using advanced physicochemical techniques. The XRD results showed that the samples produced by the microwave hydrothermal method had sharp diffraction peaks, high crystallinity and complete crystalline shape. AHM generates h-MoO3 in both hydrochloric and nitric acid environments. In particular, when the temperature rises to 200 °C, the generated h-MoO3 will be converted to α-MoO3 in a nitric acid environment, which will be generated in a sulfuric acid environment. Therefore, increasing the reaction temperature will result in the conversion of h-MoO3 to α-MoO3 in sulfuric acid solution. SEM results show that the sample prepared from hydrochloric acid solution has a complete hexagonal prism morphology, while the sample prepared from sulfuric acid solution presents a long fibrous morphology, and the sample prepared from nitric acid solution has many defects on the surface of the hexagonal prism morphology. Interestingly, sample A11 prepared in nitric acid solution showed a spherical structure. Since the generated A3, A6 and A9 samples are all stable phase α-MoO3, they have a wider band gap compared with other samples. Their particle size is up to the nanometer scale, so they have strong adsorption properties. The spherical sample A11 has excellent adsorption and photocatalytic activity.

Resource-saving and environmental protection in nuclear-grade zirconium and hafnium production

The development of efficient and environmentally friendly technological processes for processing zircon concentrate is an urgent problem in the technology of producing reactor-pure zirconium and hafnium used in nuclear power. The review presents the environmental, technical and economic characteristics of zircon decomposition processes using existing industrial technologies and provides data on the environmental safety of each technology. It is shown that current industrial technologies do not meet the criteria of sustainable development and allow emissions of toxic reagents into the environment. New applications of particularly pure zirconium and hafnium compounds which have emerged in recent decades, with impurity content of 10-3–10-5%, require less corrosive reagents than chlorine and fluorine, new resource-saving processes and equipment. Today, technical zirconium oxide with a purity of 98% is the main industrial product of zircon processing, but it allows for losses of hafnium, scandium and silicon. This is equivalent to financial losses of over USD 150 million per year. Based on the analysis of promising halogen-free technologies, a new integrated zircon processing technology is proposed which allows producing scarce hafnium, scandium and silicon compounds along with reactor-pure zirconium and its high-purity chemical compounds. The chemicals consumed in the zircon processing process are utilized in the production of mineral fertilizers, eliminating environmental pollution. The use of the highly efficient refining extraction process in a nitric acid environment using centrifugal extractors with an available tributilphosphate extractant allows us to obtain reactor metals with a purity of 99.95%. The production of high-purity zirconium, hafnium, scandium and silicon oxides meets the demand for non-nuclear products, which expands the volume of integrated zircon processing and meets the growing market demand for new functional materials. The integrated approach to zircon processing can reduce the cost of zircon by producing by-products, recycling consumed reagents and eliminating non-recyclable solid and liquid waste. This will ensure environmental protection even with relatively small volumes of reactor-pure metal production.

Corrosion and Corrosion Protection of Copper Sculptures by Formation of Composite Barrier

Nitrogen dioxide, carbon dioxide and sulphur dioxide are acidic gas and they produce corrosive medium for copper sculptures. These gases absorb moisture to form nitric acid, carbonic and sulphuric acid. It forms corrosion cell on the surface of copper and accelerate corrosion reactions. The corrosion cell formation is written as: Cu|Cu2+||H+|H2 thus corrosion reactions start and copper is oxidized into Cu2+surface and it is oxidized into Cu2+ whereas H+ ion is reduced into H2 . Nitric acid environment copper exhibits galvanic, pitting, stress, crevice, blistering, embrittlement and intergranular corrosion. The corrosion reactions change physical, chemical and mechanical properties of corroded materials. Nanocoating compound tetrahydrodibenzo[a,d][7]annulene-5,11-disemicarbazone and SiC electrospray compounds used to control the corrosion of copper in nitrogen dioxide medium. For corrosion mitigation of copper metal interface was coated with tetrahydro-dibenzo[a,d][7]annulene-5,11-disemicarbazone and SiC. The coating compound tetrahydro-dibenzo[a,d][7]annulene-5,11-disemicarbazone was synthesized in laboratory. Nozzle spray techniques used for nanocoating and electrospraying. The corrosion rate of copper was determined by gravimetric loss method at different temperatures, concentrations and days in nitrogen dioxide medium. Potentiostatic polarization technique used for the determination of electrode potential, corrosion current and current density. Nanocoating and electrospraying compounds formed a composite barrier on the surface of base metal by chemical bonding. The nanocoating and electrospray compounds adhered on base metal by chemisorptions to confirm by activation energy, heat of adsorption, free energy, enthalpy and entropy. The nanocoating and electrospray deposited on copper confirmed by Langmuir, Frundlich and Temkin isotherm. Copper formed a complex compound to interact with tetrahydro-dibenzo[a,d][7]annulene-5,11-disemicarbazone and SiC. Electrospraying SiC blocked porosities of nanocoating compound and checked osmosis process of nitrogen dioxide. Thenanocoating and electrospray compounds decreased corrosion rate and increased surface coverage areas and percentage coating efficiencies.

Effect of strontium and cesium on corrosion and contamination of 316L stainless steels during spent nuclear fuel reprocessing

The high-yield fission products of spent nuclear fuel (SNF), 90Sr and 137Cs, can deposit on the surface of facilities for SNF reprocessing plant, threatening to their safe decommissioning. To select and develop the efficient decontamination technology, the experiments for corrosion and contamination with strontium and cesium of 316 L stainless steels were performed in simulated environments of alkaline storage pond and HNO3-based PUREX process. This study analyzed the mechanism and relations of corrosion and contamination with strontium and cesium on the surface of 316 L stainless steels by combining electrochemistry and ICP-MS for the first time. When steels were exposed to the environments of alkaline and low concentration of HNO3, the presence of Sr2+ and Cs + decreased these three properties (corrosion potential, holes formed by local severe dissolution and the stability of the passive film). The results of ICP-MS demonstrated that the contamination evolution of Sr and Cs had a similar trend, and that there were significantly different contamination behaviors of steels exposed to alkaline and acidic environments. Strontium and cesium mainly deposited in the passive film of steels in both nitric acid and alkaline environments. The contamination of steels in an alkaline environment was more serious than in all nitric acid environments.

The Influence of Arc Welding Process on the Mechanical and Microstructural Characteristics of Low Carbon Steel in a Corrosive Environment

AbstractThe study is fundamentally geared toward the investigation of the influence of Manual Metal Arc (MMA) welding on the mechanical and microstructural properties of low carbon steel immersed in a 0.5 M nitric acid environment having a pH of 0.3. The corrosion and mechanical behavior of the substrates are investigated prior to and after 336 h of immersion in the test environment. The outcome of the experiment shows that the structural integrity of the immersed substrates is affected due to corrosion in the test environment. Prior to immersion, the bending resistance is seen to decrease at the welded joints relative to the blank sample and then decrease further after immersion in the test solution respectively as 3.95, 3.53, and 4.21KN. Similarly, the tensile strength of the immersed substrate decreases as compared to the unexposed and blank samples; exposed to test environment (30.60%), welded unexposed to test environment (33.25%) and for the control sample (36.33%). Furthermore, the hardness value is observed to be higher at the heat‐affected zone (HAZ) of the test substrate than at the weldment and parent metal, respectively, as 11.3, 17.7, and 15.7HV. Optical micrographs prior to and after immersion have evidently revealed that heat input during welding has caused recrystallization leading to coarser grains at the HAZ.

Mechanical Properties of Reactive Powder Concrete (RPC) Exposed to Acidic Solutions

This research work includes an experimental investigation to study the mechanical properties ofreactive powder concrete (RPC) exposed to acidic solutions. A comparative study was conductedon concrete mixes, control mix without exposure and mixes exposed to acidic solutions. RPC wasexposed to two acids (Sulfuric acid and Nitric acid) with concentration of (1.0)% for each acid. Theacidic solutions were used to study acidic rain effect and durability of RPC. Compressive strengthtest was used to study the effect of acid rain on RPC after exposure to the acid in a duration (48)hours. This exposure was done: after demolding and after (3 and 7) days curing. The maximum lossin compressive strength for Sulfuric acid and Nitric acid was (11.7 and 19.7)% respectively for afterdemolding exposure as compared with the control mix.For durability of RPC the specimens exposed to acidic solutions tested in duration (40, 50, and 60)days, to determine the compressive strength, splitting tensile strength, flexural tensile strength, andweight loss. Test results showed that RPC resistance to Sulfuric acid more than Nitric acid. Themaximum loss in compressive strength, and loss in weight were (6.20 and 2.69)% in Sulfuric acidand (22.60 and 1.32)% in Nitric acid environment respectively at (60) days as compared with thecontrol mix. The loss in splitting tensile strength and flexural tensile strength were (17.1 and 13.3)%for Sulfuric acid and (25.7 and 25.0)% for Nitric acid exposure respectively at (40) days ascompared with the control mix.

Superior Corrosion Resistance of Ti-Al-Zr Alloy in Aggressive Nitric Acid Environments

This paper describes the corrosion behavior of a Ti-based alloy, Ti-Al-Zr for aggressive nitric acid applications. Corrosion behavior of the materials was established using electrochemical polarization technique, for three process variables encountered in reprocessing plants: (a) nitric acid (1, 3 and 6 M), (b) temperature (25 and 75 °C) and (c) oxidizing ions (Ce+4 and V+5 ions). Electrochemical polarization tests established that the Ti-Al-Zr alloy was in passive condition up to a potential of 4000 mVAg/AgCl even at 75 °C, and it showed uniform corrosion. SS304L, however, showed severe intergranular corrosion at a much lower anodic potential, thus establishing better corrosion resistance for Ti-Al-Zr alloy in the aggressive nitric acid environment.

Effect of graphene oxide dosage on the deterioration properties of cement pastes exposed to an intense nitric acid environment

In this study, the effect of graphene oxide (GO) dosage on the performance of cement pastes against an extreme nitric acid environment was investigated. A significant volume of cement matrix was affected because of such attack. The loss in specimen mass and sectional area before and after acid attacks were compared to validate the relative performance between the cement mixes. Compared to the 28-day cured reference mix, the mass and sectional area losses in the acid exposed cement specimen had reduced up to 17% and 25% when the matrix was modified using 0.03 wt% GO, respectively. With an increase in GO dosage from 0 to 0.03 wt% at an interval of 0.01 wt%, it was found that the porosity of cement pastes significantly declined due to crack-arresting effects, which also explained the improved resistance of cement composites against the acidic medium. The GO presence did not influence the mineralogy of the altered cement matrix. Still, it contributed to the material stiffness, which was determined after conducting multiple characterisation studies. Thus, the GO-modified cement concrete was found to be a promising material to construct the storage structures operating under aggressive chemicals and crack inducing conditions.

Corrosion behaviour of Al-containing high Cr ferritic oxide dispersion strengthened steel in nitric acid environment

Higher chromium containing 17Cr oxide dispersion strengthened (ODS) steel (Fe-16.78Cr-4.46Al-0.5Ti-0.45Y2O3-0.36Y) with the ferritic structure are a prospective applicant fuel cladding materials for the high operating temperatures of future advanced nuclear reactors system. In this study, the microstructure, passive oxide composition and corrosion resistance of the Al-containing 17Cr ODS steel in different concentrations of nitric acid were investigated by means of SEM, TEM, XPS and electrochemical methods. The corrosion result shows that with increasing concentration of 3 M–11.5 M HNO3, open circuit potential revealed nobler potential and the potentiodynamic polarization plots exhibited a shift in corrosion potential toward transpassive region. The boiling nitric acid test after 240 h exposed in 3 M–11.5 M HNO3 showed desirable corrosion rate of ∼0.075–0.25 mm/y. As the nitric acid concentration increased, the corrosion morphology varied from smaller pits to enlarged pits with groove-like features. The improved corrosion resistance of the ODS alloy is attributed to the alloy composition, nature of dispersed oxide and passive film nature, where Al2O3 is prominently enriched. The corrosion mechanisms of ODS steel is further discussed.

Lyotropic liquid crystal phase behavior of a cationic amphiphile in aqueous and non-stoichiometric protic ionic liquid mixtures.

Protic ionic liquids (PILs) are the largest and most tailorable known class of non-aqueous solvents which possess the ability to support amphiphile self-assembly. However, little is known about the effect of solvent additives on this ability. In this study, the lyotropic liquid crystal phase (LLCP) behavior of the cationic surfactant cetyltrimethylammonium bromide (CTAB) was investigated in the model PILs of ethylammonium nitrate (EAN) and ethanolammonium nitrate (EtAN), and derived multi-component solvent systems containing them to determine phase formation and diversity with changing solvent composition. The solvent systems were composed of water, nitric acid and ethylamine (or ethanolamine), with 26 unique compositions for each PIL covering the apparent pH and ionicity ranges of 0-13.5 and 0-11 M, respectively. The LLCPs were studied using cross polarized optical microscopy (CPOM) and small and wide-angle X-ray scattering (SAXS/WAXS). Partial phase diagrams were constructed for CTAB concentrations of 50 wt% and 70 wt% in the temperature range of 25 °C to 75 °C to characterise the effect of surfactant concentration and temperature on the LLCPs in each solvent environment. Normal micellar (L1), hexagonal (H1) and bicontinuous cubic (V1) phases were identified at both surfactant concentrations, and from temperatures as low as 35 °C, with large variations dependent on the solvent composition. The thermal stability and diversity of phases were greater and broader in solvent compositions with excess precursor amines present compared to those in the neat PILs. In acid-rich solvent combinations, the same phase diversity was found, though with reduced onset temperatures of phase formation; however, some structural changes were observed which were attributed to oxidation/decomposition of CTAB in a nitric acid environment. This study showed that the ability of PIL solutions to support amphiphile self-assembly can readily be tuned, and that the ability of PILs to promote amphiphile self-assembly is robust, even with other solvent species present.

Corrosion assessment of Ni60 Nb30Ta10 metallic glass and its partially crystallized alloy in concentrated nitric acid environment

The corrosion resistance and passive film properties of Ni60Nb30Ta10 metallic glass and partially crystallized ribbon were investigated in 11.5 M nitric acid. The XRD study confirms the formation of nano-crystalline α-Ni in the amorphous matrix during crystallization at 650 °C under vacuum for 1 h. The electrochemical impedance spectroscopy, potentiodynamic polarization, and Mott-Schottky studies on the metallic glass exhibited higher corrosion resistance compared to the partially crystallized ribbon. XPS confirms the enrichment of Nb2O5 and Ta2O5 in the passive film of the glassy structure, while α-Ni is depleted in a partially crystallized alloy that affected the corrosion resistance.

Effect of thermally grown amorphous oxide film on the corrosion resistance properties of Ni50Zr25Nb25 metallic glass in nitric acid medium

In the presents work, the effects of the surface oxidation of the Ni50Zr25Nb25 metallic glass on the corrosion behavior in nitric acid environment were investigated. The oxidation kinetics at 200 and 400 °C in air environment followed two-stage rate law. SEM and XPS investigation revealed the surface of thin (106 nm) amorphous oxide film composed of NiO, Ni2O3, ZrO2, and Nb2O5 when sample was oxidized at 200 °C. However, oxidation at 400 °C resulted in a thicker (721 nm) amorphous oxide film, enriched with only ZrO2 and Nb2O5. Potentiodynamic polarization results of the thermally oxidized metallic glass at 400 °C exhibited the wider passive range and significantly higher corrosion resistance in concentrated nitric acid when compared to the as-prepared and oxidized sample at 200 °C. After polarization at 2.2 V (Vs. Ag/AgCl), thermally oxidized sample at 400 °C exhibits smooth surface while the as-prepared MG undergoes a severe dissolution in 11.5 M nitric acid.

Corrosion of the 1.4362 Duplex Stainless Steel in a Nitric Acid Environment at 333 K

Corrosion of the 1.4362 Duplex Stainless Steel in a Nitric Acid Environment at 333 K