Nitric Acid Etching Research Articles

Black etched electroless Ni–P coatings for enhanced efficiency towards alkaline water splitting

Requirements for wider use of water electrolysis for hydrogen production include the development of highly efficient, cheap, and easily made electrodes. Promising properties can be achieved with Ni–P materials. Herein, nitric acid etching (being used for blackening of electroless Ni–P coatings) resulted in enhanced efficiency towards hydrogen and oxygen evolution reactions (HER and OER) in 1.0 M KOH. For etched Ni-7.6 wt%P coating, the potential of HER at −10 mA cm−2 was about −0.20 V vs. RHE, and the potential of OER at 10 mA cm−2 was about 1.67 V, whereas for etched Ni they were −0.40 V and 1.94 V, respectively. Surface layers of etched coatings contained bundles of microrods and were enriched in O and P. Impedance measurements showed that etching caused about a 60-fold increase of CPE which can be ascribed to the development of surface area and pseudocapacitance of redox reactions, involving Ni ⇄ NiO. It is proposed that the electroactivity of Ni–NiO composite is to a large extent associated with the oxide reduction effects, involving high activity of newborn (pristine) Ni nanoparticles, acidification at the metal surface and disclosure of bare metal. Etched Ni–P coatings can be promising for the activation of electrodes for water electrolysis.

Acid treatment enhances the methane combustion activity of LaFeO3 perovskite catalyst

The catalytic combustion of methane has gained much attention as a sustainable technology, due to concerns about the environmental impact of unburnt methane emissions from the natural gas vehicles. Researchers have explored alternatives to precious metal catalysts for methane combustion, with a focus on perovskite oxides known for their excellent activity and sintering-resistance capacity. In this study, LaFeO3 perovskite material was synthesized and subsequently subjected to a nitric acid etching treatment to modify its surface. It was found that the acid preferentially dissolved La cations from LaFeO3 surface while the perovskite phase was unchanged, as a consequence, the etched LaFeO3 shows improvement in methane combustion activity. The best performance was achieved in the sample with one-hour surface etched treatment, which suggests that the appropriate surface reconstruction induced by acid treatment promotes the formation of more active Fe sites on the surface and reduces the energic barriers of methane activation. This work presents a straightforward and effective approach to tailor the exposed surface properties of perovskites, thereby enhancing their activity in hydrocarbon combustion reactions.

The effect of nitric acid � hydrofluoric acid etching solution on the shear bond strength and mode of failure of resin cement to zirconia (In vitro study)

The effect of nitric acid � hydrofluoric acid etching solution on the shear bond strength and mode of failure of resin cement to zirconia (In vitro study)

Investigating Mechanical Properties of Fabricated Carbon-Fiber-Reinforced Composites via LCD Additive Manufacturing.

Stereolithography (SLA) additive manufacturing is a method of manufacturing capable of generating complex geometric shapes with extremely high accuracy. Classic SLA uses UV curable resins, particularly polylactic acid (PLA), for part generation, but recent research has focused on utilizing this technology for the generation of various composite materials. There has been success in manufacturing composite materials using this technology, but little research has been performed on the generation of carbon-fiber-reinforced composite materials. Carbon fiber stereolithography (CF-SLA) is often overlooked due to carbon fiber's natural inability to bond with PLA. To overcome this boundary, surface modification techniques were used on chopped carbon fibers to achieve greater bonding. Here, two modification techniques were explored: a sodium dodecyl sulfate (SDS) surfactant addition and nitric acid (HNO3) etching. These methods were used to functionalize and prepare the surface of chopped carbon fiber (CF) for bonding with cured PLA resin. Treated fibers were dispersed in generic PLA resin, and tensile test specimens were printed for examining the reinforcement potential of the two treatment methods. Additional complexities arise during printing with fibers including fiber alignment, accumulation, and fiber fallout. To address these issues, a novel in-process mixing method was developed to maintain fiber dispersion. A two-level three-factor factorial design was performed for both treatment methods to determine optimal printing parameters. Through mechanical testing, atomic force microscopy, scanning electron microscopy, and contact angle measurements, the accompanying material property changes were characterized to further develop the field of fiber-reinforced liquid crystal display (LCD) additive manufacturing. After testing, it was found that composites created with SDS nanoparticle modification were stronger than both the acid etched fiber sample and plain PLA. Specifically, SDS surface treatment resulted in a 15% increase in modulus and maximum strength of the sample, mainly by enhancing the interlayer bonding between CF and PLA.

In situ self-reconstructed nanoparticle-coated cathode and anode by nitric acid etching for symmetric solid oxide fuel cells

In this study, we developed an innovative strategy to fabricate highly active cathode and anode materials by acid etching perovskite oxide (ABO3) powder. (CoxFe1-x)3O4 nanoparticles were exsoluted in situ on an etched Pr0.2Sr0.8Co0.2Fe0.8O3-δ (P0.2SCF) catalyst to reconstruct heterojunctions in air. As a result, the exsolution of (CoxFe1-x)3O4 nanoparticles on the P0.2SCF surface led to the formation of perovskite-spinel interfaces in the cathode, and the generation of CoFe alloy and CoO nanoparticles embedded on the surface of the anode in 5 % H2. Two new composite catalysts modified with nanoparticles on the P0.2SCF skeleton were simultaneously prepared through the in situ exsolution of perovskite. At 850 °C, the polarization resistance values of the anode and cathode decreased by 37 % and 57 %, respectively. Furthermore, in a single cell with LSGM electrolyte and P0.2SCF-30-GDC symmetrical electrodes, we achieved a maximum power density of 692 mW/cm2 at 850 °C under wet H2 conditions, demonstrating good electrochemical output performance. The proposed catalyst design, which employed acid etching, was not only suitable for the optimization of symmetrical solid oxide fuel cell (SSOFC) electrodes, but also for the application in other types of catalysis, providing the potential for improving the electro-catalytic activity of perovskite electrodes.

Controlled double perovskites for the efficient catalytic combustion of Cl containing VOCs

For catalytic combustion of chlorobenzene (CB), a series of cobalt-based double perovskites La2BCoO6 (BCu, Fe, Ni, Al) were synthesized by sol-gel method. These double perovskites were controllably etched by nitric acid to remove part of surface A-site and improve their catalytic activity for catalytic combustion of CB, toluene and benzene. Crystalline structure, micromorphology, surface composition, redox properties, oxidation state of the catalysts were investigated in detail by various methods. Concentration of nitric acid and the etching time were used to tune the surficial active sites of B and B′ (Cu, Co) whilst maintaining the structure. Among these double perovskites, La2CuCoO6 had the strongest oxidation ability and acidity and showed the best catalytic performance. Temperature for 90% conversion of CB (T90) on La2CuCoO6 etched by 5% nitric acid was 260 °C lower than that of as-prepared La2CuCoO6. T90 for combustion of toluene and benzene is only 240 and 290 °C, respectively. The nitric acid etching also resulted in a change in the surface charge of the Cu, Co sites, provided an oxidation cycle of Cu2++Co2+↔Cu++Co3+, which facilitated the production of surficial active oxygen, accelerated the oxygen mobility and enhanced the catalytic performance. La2CuCoO6 etched by 5% nitric acid showed good catalytic stability over 100 h testing. This work shows a novel, facile approach to prepare efficient and stable catalysts for chloride containing VOCs catalytic combustion.

The defective NH2-MIL-125(Ti) was adjusted by a simple nitric acid etching method for switching on photocatalytic NO removal

In this paper, the photocatalytic properties of NH2-MIL-125(Ti) is enhanced by using a simple nitric acid etching method to form a ligand defect strategy. The structures and properties of the samples are characterized by XRD, SEM, XPS, BET, TG, and UV–vis etc. The results display that the yield of modified NH2-MIL-125(Ti) photocatalytic NO removal experiment is significantly improved based on excellent photoresponse capacity. The optimal sample (0.1 mol/L HNO3-NH2-MIL-125(Ti)) shows excellent photocatalytic activity for NO removal under visible light irradiation (42.69%), which was 1.84 times higher than that of the original NH2-MIL-125(Ti).

Controlling Lateral Size and Thickness of Layered Double Hydroxide (LDH) Used as Conversion Layer for Corrosion Protection of AZ31 Mg Alloy

In the present study, Mg-Al layered double hydroxide (Mg-Al/LDH) was synthesized on the surface of AZ31 Mg alloy substrate via in-situ hydrothermal treatment. Synthesis parameters were changed to determine their effect on the lateral size of LDH. For this purpose, etching in nitric acid and anodizing in sodium hydroxide solution were performed as surface pretreatments. Moreover, the influence of LDH solution pH (10 and 11) on the lateral size of LDH coating was investigated. Morphology, chemical composition, and crystalline structure were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD). The corrosion resistance of the coatings was investigated by H2 measurements, salt spray, and electrochemical impedance spectroscopy (EIS). Moreover, the epoxy coating was applied on the best anti-corrosive LDH sample for assessing the compatibility and effectiveness of LDH on the corrosion properties of the substrate with the epoxy layer. At pH = 11, the lateral size of LDH was smaller than samples at pH = 10. In addition, small-sized LDH, as well as LDH/epoxy coating, revealed enhanced corrosion protection.

Fabrication of a durable brass mesh capable of rapid transformation between two modes of liquid transportation

Low cost, process controllability, and durability have been the key problems in the application of superhydrophobic materials, and there are many difficulties in achieving these goals. A simple ultrasound-assisted nitric acid etching method is now described for the construction of coral-like metal structures on the surface of a brass mesh pipe. The structures are formed by the different corrosion rates of the two metals in the alloy during etching. These structures exhibit superoleophobic characteristics in water and, following modification by immersion in aqueous sodium laurate solution, superhydrophobic characteristics in air. The surface wettability of the pipe can be converted multiple times within one hour to facilitate two modes of liquid transportation, in water and in air. The pipe material has excellent durability, withstanding severe mechanical contact including fingertip friction, arbitrary folding, knife scratching, and load friction, without significantly altering the surface wettability. This novel material can be prepared using a simple, controllable, low-cost, and environmentally friendly method and offers a new direction for the development of multi-interface liquid transportation devices.

Studying the shape of nickel particles when machining by ultrasound-aided electric discharge

This paper presents a model for producing nano-microparticles by ultrasound-aided electric discharge. After machining, scanning electron microscopy (SEM) was used to check the shape and size of the nickel particles; they were found to be distributed in a few micrometers to 80 [Formula: see text]m range. The nickel particles were regular spherical shaped, and the grain sizes of the particles were different. In addition, many small particles were attached to the surface. Various methods such as inlay polishing, nitric acid etching, and direct SEM imaging were employed to determine the hollow nickel particles such as very thin particles, large thickness grains, hollow sponge-like structures, and solid particles.

Electrochemiluminescence resonance energy transfer system based on ox-MWCNTs-IGQDs and PdAg nanosheets for the detection of 5-fluorouracil in serum

In this work, a novel electrochemiluminescence energy resonance transfer (ECL-RET) immunoassay based on ox-MWCNTs-IGQDs and PdAg nanosheets (PdAg NSs) was established for the ultrasensitive detection of 5-fluorouracil (5-FU) in serum. Exposure of graphene quantum dots by nitric acid etching of multi-walled carbon nanotubes to form ox-MWCNTs-IGQDs, which exhibited excellent electrochemiluminescence intensity. The prepared PdAg NSs have the characteristic of large specific surface area and low toxicity. Furthermore, ox-MWCNTs-IGQDs as ECL donor and PdAg NSs as ECL acceptor can directly carry 5-FU coating antigens and antibodies, respectively. Interference due to the introduction of other bridging molecules can be avoided. Based on the principle of competitive immunity, the 5-FU detection substance and 5-FU coating antigen will co-compete for the specific binding site on the scant antibody, realizing the efficient detection of 5-FU. Under optimal conditions, the proposed ECL immunosensor for 5-FU detection exhibited high sensitivity with a wide linear range from 0.0005 ng/mL to 500 ng/mL and a low detection limit at 0.17 pg/mL. This work took a simple approach to design the ECL immunosensor, the sensor had certain feasibility for the detection of 5-FU in the serum of cancer patients, and provided a new way for the detection of other small molecule anticancer drugs in the future.

Microstructure, composition and formation mechanism of ultra-black surfaces on the electrodeposited nickel-phosphorous coatings

Light absorbing materials are of practical importance in the production of optical devices in aerospace technology. A new method of light absorbing coatings preparation on the basis of electrodeposited nickel-phosphorus coatings has been proposed. Modification of the electrolyte for nickel-phosphorus plating by the addition of saccharine allowed preparing an ultrablack surface with a reflectance coefficient less than 0.5%. Chemical composition of both surfaces has been studied using X-ray photoelectron spectroscopy. The mechanism of their formation has been proposed. It has been found that etching in nitric acid leads to the partial oxidation of both surfaces with the formation of needle like microstructure.It also results in surface enrichment with phosphorus and formation of nickel phosphides particles of the variable composition. Products of the coating oxidation represent the matrix of amorphous nickel polyphosphates and polyphosphoric acids where fine Ni-P particles are distributed. Such composite structure is a well light absorbing medium. Formation of hypophosphite protective layer on the Ni–P coating obtained from saccharin free electrolyte reduces the thickness of light absorbing layer and changes its composition. Thus light absorbance ability of the coatings can be caused by both distribution of fine nickel-phosphorus particles in dielectric matrix and specific microstructure of their surfaces.

Selective etching of Sm0.5Sr0.5CoO3-δ ceramic for solar evaporator with photocatalytic purification

The ultimate goal of solar driven water evaporation is to obtain clean water without volatile organic pollutants. Current strategies mainly depend on the integration of the photo-thermal conversion and photocatalytic degradation by a multi-step composite technique. In this work, a facile nitric acid etching method was adopted to prepare the photothermal-catalytic bifunctional material (Sm0.5Sr0.5CoO3-δ-Co3O4). The effect of the acid-etching treatment on the Sm0.5Sr0.5CoO3-δ surface evolution was investigated. The Sm0.5Sr0.5CoO3-δ (SSC5) surface was selectively reconstructed, and the catalytic active B-site cobalt cation was randomly exposed after the acid-etching treatment. The unique structure of SSC5-Co3O4 was beneficial to the electrons transport between Co3O4 and SSC5, as well as the solar absorbance. The nitric acid-etched SSC5 honeycomb ceramic exhibited a solar absorption of 80%, resulting in an evaporation rate of 7.25 kg·m−2·h−1 under a simulated sunlight of 1000 mW·cm−2. Besides, the etched SSC5 exhibited the ability for pollutant (Congo red) degradation. The as-prepared acid-etched SSC5 honeycomb ceramic could integrate the solar evaporation with pollutant degradation, which has a promising application in the pure water production.

Scratch testing of electrolytic nickel coatings on a carbon fiber reinforced plastic substrate

A method for quantitative assessment of the strength of nickel coatings adhesion to CFRP KMU-11-M2.200 by the sclerometry method with the use of a laboratory scratch tester is proposed. The method has expanded capabilities due to the operation according to two loading programs and an additional technique for recording the moment of destruction of the coating by changing the scratch resistance force. The appearance and schematic diagram of the non-standard ST-01 scratch tester, developed at the STCU VIAM, are presented. Scratch testing of nickel coatings obtained by the traditional electrochemical method in a bath and by the method of local brushing was carried out, with two methods of pre-treatment of the carbon fiber surface before nickel plating being considered (sandblasting and nitric acid etching). The surface morphology was investigated by optical microscopy and the thickness of nickel coatings deposited in the bath and by brushing was determined. By combining the obtained scratches with the plots of the indenter load and the resistance force against the indenter displacement, the critical load is determined at which continuous destruction of the coating with delamination is recorded. Based on the formulas of P.Benjamin and K.Weaver, the adhesion strength of nickel coatings was calculated and it was shown that the adhesion strength of nickel coatings deposited in a bath is 1.6 times higher than that of coatings obtained by brushing. The results of scratch testing are presented, and the nature of the destruction of nickel coatings at an indenter position of more than 25 mm is described.

Corrosion effects on the nanotribology of a Ni62Nb38 metallic glass

The onset of corrosion in 0.1 M nitric and hydrochloric aqueous solutions and its effect on the friction and wear of a Ni62Nb38 MG have been investigated by AFM, XPS and SEM. Depending on the acidic solutions, the properties of the oxide layers grown on Ni62Nb38 MG differ, which affects the tribological response of the surface. A clear transition from shearing to ploughing friction is observed for as-spun Ni62Nb38. After etching in nitric acid, the onset of ploughing is retarded, and wear is reduced. In contrast, ploughing is suppressed after immersion in HCl. In that case friction and wear are dominated by adhesion and material transfer.

Increasing the titanium alloys durability due to modifications by vibro-abrasive processing of the strengthened surface layer

It is shown that vibroabrasive treatment of hardened titanium alloy specimens contributes to an increase in their durability. This effect is explained by the removal of a defective surface layer containing microcracks and subject to the influence of residual tensile stresses. It is shown that the proposed stage of vibro-abrasive processing with ceramic granules makes it possible to almost completely remove iron introduced after vibro-impact surface hardening, which makes it possible to exclude the operation of etching in nitric acid from the technological process. The current state of research on durability in world science is briefly presented.

Evaluation of the Effect of the Microscopic Glass Surface Protonation on the Hard Tissue Thin Section Preparation

In this study, a new procedure for mounting tissue blocks was described while cutting and grinding the section remains tightly bound to the inert glass surface both chemically and micro mechanically allowing good quality specimens for staining and microscopic analysis. The micromechanical interlocking was achieved by using of frosted glass, the chemical binding was made with 10-methacryloyloxydecyl dihydrogen phosphate monomer (10-MDP) containing bond material. The glass surface activation was achieved by nitric acid etching and the surface was characterized by zeta potential, X-ray photoelectron spectroscopy (XPS), and contact angle measurements. Cylindrical samples were prepared from epoxy embedding materials, cortical bovine bone, and dental titanium to investigate the shear bond strengths (SBS) to microscopic glass slide compared to a routinely used thermoplastic adhesive. Based on the experiments it was found that the micromechanical retention combined with MDP containing bond material improved the SBS data compared to the thermoplastic adhesive. The acid etched glass became positively charged that significantly increased the SBS data of bone and titanium compared with the uncharged version. Therefore, the thickness of the undecalcified bone section with metal can safely reduce to improve histological microscopic analysis.

ELECTRODEPOSITION OF COPPER IN ULTRASONIC FIELD FROM SPENT ETCHING SOLUTIONS

It is studied the regeneration and utilization possibility of spent nitric acid solutions for copper and its alloys etching for the creating an environmentally clean closed-cycle production of regenerated electrolytes. It is established that some difficulties arise when using the electrochemical method in the regeneration process of these solutions: during copper electrodeposition from spent copper-containing nitric acid solutions, nitric acid decomposes with vigorous evolution of nitrogen dioxide, which prevents copper ions reduction. In order to suppress the side process, it was proposed to partially neutralize the solution, not reaching the pH of copper hydration (pH 4-5). It is revealed that a decrease in the concentration of metal cations occurs due to partial neutralization of the nitric acid contained in the solution by concentrated alkali solution. The pulsed electrolysis mode was used to increase the efficiency of the metal ions electrodeposition process from dilute solutions. It is established that the using of pulsed electrolysis can reduce diffusion difficulties that arise in a dilute spent nitric acid copper-containing solution, thereby intensify the process of copper electrodeposition. It is showed that the prospects of using ultrasound to increase the rate of the copper electrodeposition process and improve the quality of the resulting coating. It is studied the ultrasound field effect on nucleation during copper electrodeposition in a pulsed mode from a partially neutralized electrolyte simulating the spent nitrate solution of etching copper alloys on various materials by the potentiostatic. It is established an increase in the number of copper nucleus that form on the studied substrates (graphite, copper, steel) at the initial time under the action of an ultrasonic field. It is concluded that the use of ultrasound allows to intensify the process of metal electrodeposition. An increase in current efficiency during copper electrodeposition and an increase in the copper extraction degree using ultrasonic field are achieved at lower cathodic current densities in a pulse. It is substantiated using of graphite foil and steel as cathode materials in the copper extraction from the spent nitric acid etching solution.

Reexamination of Nucleation and Growth Behavior of Zn during Zincating on Al: Role of Nitric Acid Etching

Deposition of various coatings on Al surface is required for variety of functional applications such as for better corrosion resistance, improvement in conductivity, wear resistance etc. These coatings are normally applied on Al surface followed by well-known zincating process (galvanic displacement) in order to obtain subsequent adherent overlayer coatings. Adhesion of these overlayers depends on uniformity of Zn films on Al surface and researchers normally follow either single zincating or double zincating process to eliminate oxide layer interference. However, it has been established over the years that double zincating is a better technique in comparison to single zincating to produce a uniform Zn-films on Al surface. It is to mention here that Al substrate undergoes nitric acid dip followed by single zincating prior to double zincating and is a very important step. A quiet good amount of research has already been devoted to obtain various adherent coatings on Al and Al-alloys and to analyze the nucleation mechanism during single and double zincating processes. However, the underline mechanism of nitric acid etching and its role on subsequent Zn-nucleation is yet to be fully understood. In view of this, in the present study, a systematic effort has been made to elucidate the role of nitric acid etching followed by single zincating on Zn nucleation and growth mechanism during subsequent second zincating. For this, we have studied the time-dependent zinc nucleation on 99.95% pure Al during single as well as double zincating. These Zn-nucleation and growth behavior on Al surface was monitored using AFM, FESEM and FIB-cut cross section image investigations in detail. Difference in nucleation and growth pattern of Zn on Al during two zincating processes was analyzed. Apart from these, the porous surface obtained after nitric acid dissolution was investigated in depth under AFM and FESEM along with EDS. Non-gravimetric method such as Rutherford Backscattering Spectrometry (RBS) was used to determine the deposition rate of Zn during competitive galvanic deposition of Zn and alkaline dissolution of Al while zincating. The Zn grain size obtained from AFM image was verified by GIXRD analysis. Open circuit potential (OCP) was monitored during single as well as double galvanic displacement processes to understand Zn nucleation behavior and correlated with the morphological data. The observed results will be discussed in terms of electrochemical processes involved, change in chemical nature of the Al surface and porous layer formation due to nitric acid etching and thermodynamic supersaturation on Zn nucleation. Figure 1

Fabrication of Zinc Substrate Encapsulated by Fluoropolyurethane and Its Drag-Reduction Enhancement by Chemical Etching

A fluoropolyurethane-encapsulated process was designed to rapidly fabricate low-flow resistance surfaces on the zinc substrate. For the further enhancement of the drag-reduction effect, Cu2+-assisted chemical etching was introduced during the fabrication process, and its surface morphology, wettability, and flow-resistance properties in a microchannel were also studied. It is indicated that the zinc substrate with a micro-nanoscale roughness obtained by Cu2+-assisted nitric acid etching was superhydrophilic. However, after the etched zinc substrate is encapsulated with fluoropolyurethane, the superhydrophobic wettability can be obtained with a contact angle of 154.8° ± 2.5° and a rolling angle of less than 10°. As this newly fabricated surface was placed into a non-standard design microchannel, it was found that with the increase of Reynolds number, the drag-reduction rate of the superhydrophobic surface remained basically unchanged at 4.0% compared with the original zinc substrate. Furthermore, the prepared superhydrophobic surfaces exhibited outstanding reliability in most liquids.