Chemical Corrosion Method Research Articles

Oxygen-functionalized Fe3O4@o-polypyrrole acting as high-efficiency oxidase mimics and their application in glutathione colorimetric sensing

The enzyme-like properties of nanozymes may be considerably affected by the structure and surface groups, which thus need to be optimized. Here, through a simple NaOH chemical corrosion method, the chemical structure similar to N-Methylpyrrolidone (NMP), which possessed intrinsic oxidase-like activity, was introduced into polypyrrole (PPy), and then this nanomaterial became oxygen-functionalized PPy (o-PPy) with excellent oxidase-like activity from PPy without this property. Furthermore, after compounding magnetic Fe3O4, the obtained nanocomposites Fe3O4@o-PPy nanoparticles (Fe3O4@o-PPy NPs) showed superiorities in separation during synthesis and real-time control of enzyme catalysis. Studies have found that the enzymatic activity of Fe3O4@o-PPy NPs depended on the amount of functionalized oxygen and the conjugation extent of o-PPy. Fe3O4@o-PPy NPs had efficient oxidase-like activity under a wide range of pH and temperature. Based on the oxidase-like activity of Fe3O4@o-PPy NPs, a colorimetric sensor for glutathione (GSH), which presented rich color changes and satisfactory colorimetric resolution by adding the amaranth, was realized. We believe that the functional modification and structural regulation of PPy can not only realize its wider application but also promote the discovery of novel and efficient nanozymes.

Pore structure regulation of aluminum powder as a filler for high energy solid propellants

Aluminum (Al) powder, as a high-energy metal combustible agent, has advantages such as high calorific value and low cost. It has important research value in energetic materials. However, due to the Al2O3 layer on the surface of Al powder, the contact area between Al powder and oxidant components is reduced, resulting in a decrease in its energy release performance. In this paper, a modified Al powder with porous structure was prepared by chemical corrosion method to solve the problem that its small contact area with oxidant components affects its energy release performance. The study found that when the concentration of HF solution is 3.0 wt%, the removal effect of the oxide layer of Al powder is most effective, with a surface O element content of only 0.6 wt% and a uniform porous structure on the surface of Al powder. In addition, experiments have shown that nano CuO can be well filled into the pore structure of modified Al, increasing the contact area between Al powder and oxidant. This work provides a novel and simple research approach for effectively improving the energy release performance of Al based energetic materials.

A Gas-Liquid Sensor Functionalized With Graphene-Oxide on Chalcogenide Tapered Fiber by Chemical Etching

This work presents a gas-liquid sensor based on chalcogenide etched-tapered fiber (ETF) functionalized with graphene oxide film. Unlike the preparation of conventional tapered fiber sensors, the core diameter of the optical fiber of this gas-liquid sensor was kept constant, and part of its cladding was removed via the chemical corrosion method that the fiber optic modes were the invariant. The energy distribution of transmission mode in the original fiber and tapered fiber is simulated respectively, and obtained the conclusion that the tapered fiber structure has higher sensing sensitivity. The sensors could detect VOCs such as formaldehyde (HCOH) and butane (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> ) in the mid-infrared band. Results showed that the ETF sensor had a high detection sensitivity of both HCOH solution (2.6731 a.u./mg·mL <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> ) and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> gas (0.2773 a.u./vol.%). A layer of graphene oxide (GO) film was coated on the ETF to further improve the sensitivity of the sensor. The GO coated etched-tapered fiber (GO-ETF) sensor’ sensitivity was substantially improved owing to the strong hydrophilicity and biocompatibility of GO which can absorb bioactive molecules. The high detection sensitivity of both solution and gas were 4.5091 a.u./mg·mL <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> and 0.4812 a.u./vol.%, respectively, which were 1.69 and 1.74 times higher than that of the sensor without a coating of GO film. The results further showed that the sensor had a rapid response speed, low detection limit, good repeatability, and stability.

Fabrication and study of Raman signal enhancement of pyramid/nano-Ag structured Silic substrate

The pyramid-structured silicon substrate was successfully fabricated by a chemical corrosion method with an average thickness of about 1 - 3 &amp;mu;m with the optimal parameters such as corrosion temperature of 70oC, corrosion time of 5 min, concentration KOH of 3 M and isopropyl alcohol concentration of 1 M. After that, the silver nanoparticles layer (thickness 20 nm) was coated on the silicon substrate by a sputtering method to enhance the SERS signal. The results proved that the Pyramid/nano Ag structure silicon substrate showed the enhancement effect of Raman signal, and Rhodamine 6G pigment in food at low concentration (10-6 M) was detected and the enhancement factor was 9.7 &amp;times; 102.

High internal phase emulsions and their applications in functional material preparation

High internal phase emulsions (HIPEs) are usually defined as a kind of superconcentrated emulsions, in which the minimum internal phase volume fraction reaches to 0.74. Comparing with traditional emulsions, high internal phase emulsions (HIPEs) tend to be highly viscous, solid-like emulsions because of their higher internal phase volume fraction. Thus, focusing on their microstructure, the shape of the oil droplets turned from spheres to irregular polyhedrons separated by a continuous phase film, leading to the deformation of the inner phase droplets. Obviously, the selection of suitable and effective stabilizers based on different stabilization mechanisms is vital for the emulsification process. Up to now, mainly three types of stabilizers based on dissimilar stabilization mechanisms have been successfully developed, including traditional surfactants, solid particles, and low molecular weight or macromolecular gelators. Given that the unique structural features, the wide applicability of HIPEs in pharmaceutical formulations, controlled-release deliverers, cosmetics industries, cold chain logistics and fatty food products has received considerable attentions. Moreover, owing to the characteristics of high viscosity and large interface film area, it is feasible to use high internal phase emulsion as a template to prepare porous functional materials, and the polyhedral structure of the internal droplets endows the final obtained porous material with higher specific surface area, higher porosity and lighter weight. Comparing with the other traditional methods, such as microemulsion method, chemical corrosion method, phase separation method, and so on, the parameters of porous material, including pore distribution, pore capacity and pore density can be easily and precisely controlled by altering the internal and external phase volume fraction, the type of stabilizer and other factors. Overall, the porous materials based on HIPEs template possess many advantages, including low cost, high capacity and excellent reversibility showing huge potential in gas adsorption, separation and enrichment, drug delivery and other practical fields. The present review provides the advanced progresses of preparation of HIPEs and applications in functional materials, with sophisticated porous structures and desirable environmental adaptabilities. Initially, we clearly summarize the synthesizing strategies in regard to both corresponding mechanisms and typical examples developed in recent years, including oil-in-water (O/W) HIPEs, water-in-oil (W/O) HIPEs, oil-in-oil (O/O) HIPEs, high internal phase supercritical fluid emulsions, high internal phase ionic liquid emulsion and high internal phase deep eutectic solvent emulsion. Subsequently, we also clearly discuss in detail the selection of stabilizers including traditional surfactants, solid particles, and low molecular weight or macromolecular gelators, and the influence of various external environmental factors on the stability of high internal phase emulsions (the features of phase, temperature and electrolyte). Meanwhile, we further look forward to their potential applications in functional material preparation, including the functional porous materials, flexible wearable devices and stimulus responsive material. Moreover, the limitations of the existing porous functional materials based on high internal phase emulsion are discussed, including inadequately mechanical performance and unsatisfactory biocompatibility, which will provide significant guidance for synthesizing strategies and practical application in the future. In the end, the current challenges and perspectives on the future development of functional HIPEs materials are also discussed.

Visible light response ZnO–C3N4 thin film photocatalyst

Nanoflower-like ZnO–C3N4 thin film with a porous net structure was successfully synthesized by a simple chemical corrosion method. The prepared ZnO–C3N4 thin films presented remarkable photocatalytic activities for the degradation of methyl orange under visible light irradiation, and more than 90% methyl orange was removed from water by ZnO–C3N4 composite. Meanwhile, the ZnO–C3N4 composite presented an enhanced photocatalytic stability. The loading content of C3N4 had a great effect on the photocatalytic performance. Moreover, the photocatalytic activities were higher in acidic media than those in alkaline conditions. The adsorption of methyl orange was enhanced, and the recombination of photogenerated electrons and holes was suppressed with a suitable content of C3N4. However, too much loading content of C3N4 resulted in a poor dispersion of C3N4 as the aggregated C3N4 can behave as recombination centers. In addition, the prepared ZnO–C3N4 thin film can be used for the water splitting in water–methanol system under simulated solar light irradiation.

Analysis of real contact area and re-lubrication in oscillating bulk forming process by corrosion method

Oscillating method has been applied to bulk forming process due to the load reduction and high yield. The main cause of load reduction is the rebuilding of lubricating film during the back stroke of the die. A chemical corrosion method using an oscillating T-shape compression (OTC) test was employed to analyze re-lubrication and real contact area (RCA) in oscillating bulk forming process. Conventional T-shape compression (CTC) test and OTC test with three different frequencies were compared. Moreover, lubrication in compression and extrusion, which are two typical plastic deformations in T-shape test, were analyzed separately. The differences in RCA and re-lubrication were analyzed by optical microcoordinate measurement (OMC) and confocal scanning laser microscopy (CSLM). The mixed lubrication condition and re-lubrication degree were analyzed by measuring 3D roughness parameters and specimen geometry. By applying the corrosion method, the two main problems (i.e., the effective re-lubrication observation and the actual friction condition under load) can be expressed by the different degrees of corrosion. Re-lubrication was confirmed by the chatter marks expanding in the circumferential direction. Unlike in conventional forming, mixed lubrication condition was guaranteed by the re-lubrication, and the thick lubricant film prevented the generation of scratches. Furthermore, the RCA and lubrication condition were subjected to oscillating frequency. Results showed that a higher frequency produced more sufficient lubrication.

Fabrication and capillary characterization of axially micro-grooved wicks for aluminium flat-plate heat pipes

A novel micro V-grooves wick, fabricated by ploughing–extrusion (P–E) method and then surface treated by chemical corrosion, was developed for enhancing the performance of aluminium flat-plate heat pipes (AFHPs). Capillary rise tests with acetone were performed to characterize the capillary performance of the wick structures. An infrared (IR) thermal imaging method was utilized to monitor the capillary rise processes. The effects of solution concentration and corrosion time on the capillary performance of the wicks were investigated. Experimental results indicate that the capillary rise height of the corroded aluminium grooved wicks was substantially higher than that of non-corroded wick. However, the concentration and corrosion time are to be regulated with care in order to achieve optimum capillary performance. In this study, the optimal corrosion parameters were determined to be 1.5 mol/L NaOH for 10 min, which resulted in the best capillary performance parameter (K/Reff) of 6.98 µm—an increase of approximately 207% compared to the one with no corrosion. This study demonstrates that the combination of P–E process and chemical corrosion method is a convenient and effective means to enhance the capillary performance of grooved aluminium wicks and the heat transport capability of AFHPs.

Nanoporous Surface Modifications through Dealloying of Al–Ti Alloy

TiO2 nanoporous structure was formed on the surface of Al–Ti alloy through a facile chemical corrosion method. The alloy composition, NaOH concentration, reaction time, and temperature played important roles in determining the morphology, elemental composition, phase composition, and the hydrophilic properties of the as‐dealloyed samples. A uniform pore size distribution of a three‐dimensional network structure was obtained with the diameter ranged from 100 nm to 2 μm. The obtained TiO2‐based crystalline material exhibited good surface hydrophilic activity and light absorbency, which opened avenues in formation of porous nanostructures with high performance and low cost.

Effect of different surface states of FeCrAl alloy wires on terahertz radiation

Terahertz radiation from 100 to 400 cm−1 of FeCrAl alloy wires has been studied by Fourier Transform Spectrometer. The different surfaces of the alloy wires prepared by physical cleaning method (polished by sandpapers) and chemical corrosion method (corroded in HCl and HAc solution), induced different terahertz radiation. Energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) analysis confirmed that the surface oxide included α-Fe2O3, FeO, Fe3O4, Cr2O3 and Al2O3 with the thickness of 5 μm. Terahertz spectra showed that with the increase of the oxide content, the intensity of the terahertz radiation obviously decreased in the range of 50–500 cm−1. Attributing to the existence of oxide with the magnetic energy changed in the demagnetization process, a red shift of the terahertz spectra was found. Surface roughness and carbide content weakly affected the terahertz radiation intensity. Finally, the terahertz radiation mechanism derived from the different surface states has been discussed. These results are expected to provide new perspectives for the application of broadband terahertz sources.

Facilely synthesis of 3D CuxO–Cu nanostructures as binder-free electrode for supercapacitors

3D CuxO–Cu nanostructures were synthesized through a simple chemical corrosion method and were employed as binder-free electrodes for supercapacitors. Owing to the direct growth of the active materials onto the Cu foam without any binders, and the 3D interconnected structure ensures a highly conductive network favorable for electron transfer, the as-prepared electrode exhibit a high specific capacitance of 111mFcm−2 at 0.5mAcm−2 and a better rate capability of 80mFcm−2 at 10mAcm−2. Besides, the CuxO–Cu//AC asymmetric supercapacitor can deliver a high energy density of 34.36μWhcm−2, thus showing great potential for supercapacitor applications.

Straight and Segmented Structure Evanescent Wave Sensor With Different Sensing Region Length

A comparative study of optical fiber evanescent wave sensors based on straight and segmented structure (SS) has been carried out. The waveguide modes of the straight and the SS are simulated and analyzed using beam propagation method, which shows the high-order modes are excited repeatedly at the first transition of the each segmented region. The sensors are made using the chemical corrosion method. The sensitivity of the sensors is tested using the different concentration methylene blue solution. With the fixed core diameters, the sensitivity of the SS sensor is higher than that of the conventional single straight sensor, while the sensing region length of the former (1 and 1 cm) is shorter than that of the latter (3 cm). The experimental results are consistent with theoretical models and simulation analysis. The SS can effectively improve the sensitivity of the sensor, and has sufficient robust, which is suitable for materials spectrum measurements.

The preparation of Ni5P4/Ni composite via a chemical corrosion method and its application in lithium ion batteries

The chemical corrosion of red phosphorus on Ni foam is studied, which leads to the growth of Ni5P4 on the surface of Ni foam. The morphology and size of the as-prepared Ni5P4 are studied by field-emission scanning electron microscopy (FE-SEM), which indicate that the Ni5P4 is composed of particles with a mean size of about 500nm and microflowers with a mean size of about 10μm. The electrochemical property of Ni5P4/Ni as anode for lithium ion batteries is studied by conventional charge/discharge test, which shows obvious voltage plateaus in charge/discharge curves, endowing it with potential application in lithium ion batteries.

A 147 fs mode-locked erbium-doped fiber laser with a carbon nanotubes saturable absorber in evanescent field

A saturable absorber of 3.9% modulation depth was prepared on the surface of a fiber clad with single-walled carbon nanotubes (SWCNT) using chemical corrosion method. An all-fiber Er-doped fiber laser was setup with a ring cavity, and was mode-locked successfully by evanescent field mode-locking using prepared saturable absorber of single-walled carbon nanotubes. A 147 fs mode-locking pulse is obtained near 1556 nm with a 3 dB bandwidth of 24 nm. The output power is 21 mW at a pump power of 520 mW, corresponding to a pulse energy of 0.14 nJ with a repetition rate of 150 MHz.

Bioactive composite gradient coatings of nano-hydroxyapatite/polyamide66 fabricated on polyamide66 substrates.

Tightly bonding of bioactive coating is the first crucial need for orthopaedic implants. This study describes a novel and convenient technique to prepare bioactive coating with high adhesion on orthopaedic substitutes made of polymeric matrix. Here, a chemical corrosion method has been adopted to fabricate a coating on the surface of injection-moulded polyamide66 (PA66) substrates by corrosive nano-hydroxyapatite/polyamide66 (n-HA/PA66) composite slurry. Scanning electron microscopy observation shows that a porous chemical corrosion region presents between the coating and dense PA66 substrate. Energy-dispersive X-ray spectroscopy analysis indicates that the chemical corrosion region is mainly composed of PA66 matrix, and the coating layer is an n-HA-rich layer. Both the pore size and n-HA composition increase gradually from the polymeric substrate towards the coating surface. Mechanical testing shows the bonding strength can reach 13.7 ± 0.2 MPa, which is much higher than that fabricated on polymeric matrix by other coating methods. The gradual transition in coating structure and composition benefits for the interface bonding and for the surface bone-bonding bioactivity. Subsequent cell experiments corroborate n-HA-rich coating and a porous structure is benefitting for cell attachment and proliferation. The convenient coating method could be popularized and applied on similar polymer implants to produce a tightly and porous bioactive coating for bone tissue regeneration.

Fabrication of superhydrophobic surfaces with hierarchical rough structures on Mg alloy substrates via chemical corrosion method

Superhydrophobic surfaces are commonly fabricated by a combination of hierarchical rough structures and low surface energy materials. The hierarchical rough structures of micrometre-scale lump-like structures and sub-micrometre-scale concave–convex structures were firstly and directly fabricated on the surfaces of magnesium (Mg) alloy plates by a simple chemical corrosion. Then, chemical modification with fluoroalkylsilane (FAS) and stearic acid was employed to decrease surface energy. Effect of the composition of chemical corrosive solution on the surface morphology was also studied. Results show that a good superhydrophobic surface on Mg alloy substrates with a 163.4° static water contact angle and 8° rolling angle was obtained via chemical corrosion and FAS modification. The chemicals NiSO4 and NaH2PO2 are both essential to fabricate the hierarchical rough structures needed by the superhydrophobic surfaces.

Highly Luminescent YVO4−Eu3+ Nanocrystals Coating on Wirelike Y(OH)3−Eu3+ and Y2O3−Eu3+ Microcrystals by Chemical Corrosion

Highly luminescent YVO4−Eu3+ nanocrystals (NCs) coating on wirelike Y(OH)3−Eu3+ and Y2O3−Eu3+ microcrystals were synthesized by a chemical corrosion method, that is, first preparation of Y(OH)3−Eu3+ wirelike microcrystals by a hydrothermal method, and subsequently chemical corrosion with NaVO4 solutions through a second hydrothermal treatment. The crystal structure, morphology, and optical properties of the composites were characterized and compared with those of the general nanoparticles (NPs) obtained by a one-step hydrothermal process. The results indicate that chemical corrosion method yields high-quality YVO4−Eu3+ NCs in the composite grown from exterior to interior, compared with the directly hydrothermal NPs grown from interior to exterior. In addition, luminescent intensity for YVO4−Eu3+ in the composite was remarkably increased compared with that of NPs, due to more efficient energy transfer from VO43- to Eu3+ ions, and was further increased up to level of the the bulk materials after being annea...