Facile Chemical Etching Research Articles

Investigation on R141b convective condensation in microchannel with low surface energy coating and hierarchical nanostructures surface

A facile chemical etching method for fabricating copper surface with hierarchical nanostructures and low surface energy coating was adopted in this study. Experimental investigation on the condensation heat transfer of refrigerant R141b in a rectangular microchannel with hydraulic diameter of 0.67 mm was conducted. The mass flux was of the range from 70 kg/(m2 s) to 850 kg/(m2 s). The effects of surface wettability and wall sub-cooled on the flow and heat transfer characteristics were analyzed. For channels with same nanostructures, the increase of contact angle resulted in the increase of heat transfer coefficient, but it had little effect on the pressure drop during condensation. The experimental results showed that the channel with the contact angle of 21.6° had a 12.81% enhancement in the heat transfer coefficient compared to the original copper channel with the contact angle of 12.8°. Moreover, a composite channel with gradient contact angle had a 16.67% enhancement in the heat transfer coefficient compared to the original one. The hierarchical nanostructures had significant influences on the heat transfer characteristics and pressure drop during convective condensation in microchannel. A higher mass flux resulted in higher heat transfer coefficient and pressure drop, while a higher wall sub-cooled temperature caused a lower heat transfer coefficient during the R141b condensation in a microchannel.

Tailoring the robust superhydrophobic silicon textures with stable photodetection properties

Surface hydrophobicity of silicon with sound durability under mechanical abrasion is highly desirable for practical needs. However, the reported micro-pyramid/nanowires structures suffer from the saturation characteristics of contact angle at around 132 degree, which impede the promotions toward reaching the state of superhydrophobicity. The present study focuses on the realization of two-scale silicon hierarchical structures prepared with the facile, rapid and large-area capable chemical etching methods without the need of lithographic patterning. The designed structures, with the well combination of microscale inverted pyramids and nanowire arrays, dramatically lead to the increased wetting angle of 157.2 degree and contact-angle hysteresis of 9.4 degree. In addition, the robustness test reveals that these hierarchical textures possess the narrow contact-angle change of 4 degree responding to the varied pH values, and maintain a narrow deviation of 2 degree in wetting angle after experiencing the abrasion test. Moreover, the highly stable photodetection characteristics of such two-scale structures were identified, showing the reliable photocurrents with less than 3% of deviation under wide range of environmental humidity. By adopting a simple chemical treatment, the wetting control is demonstrated for reliable transition of superhydrophobicity and superhydrophilicity.

Biomimetic high-intensity superhydrophobic metal rubber with anti-corrosion property for industrial oil–water separation

In this work, a superhydrophobic metal rubber with excellent water repellency, mechanical durability, corrosion resistance and oil/water separation properties was prepared by a facile and scale-up chemical etching method and a straightforward modification.

Hierarchical porous hollow FeFe(CN)6 nanospheres wrapped with I-doped graphene as anode materials for lithium-ion batteries.

Hierarchical porous hollow FeFe(CN)6 nanospheres were synthesized via a facile anisotropic chemical etching route at different temperatures. Herein, we integrated these FeFe(CN)6 nanospheres and conductive iodine-doped graphene (IG) into a lithium-ion battery (LIB) system, FeFe(CN)6@IG. The hollow Prussian-blue type FeFe(CN)6 nanospheres with an average particle size of 230 nm are uniformly and tightly encapsulated by IG sheets. As an anode material for LIBs, the fabricated FeFe(CN)6@IG exhibits high specific capacity, excellent rate properties, and superior cycling stability. A reversible capacity can be maintained at 709 mA h g-1 after 250 cycles at a current density of 1000 mA g-1. Even at a current rate of 2000 mA g-1, the capacity could reach 473 mA h g-1. This facile fabrication strategy may pave the way for constructing high performance Prussian blue-based anode materials for potential application in advanced lithium-ion batteries.

Flower-like Bi0.9La0.1FeO3 microspheres modified by reduced graphene oxide as a thin and strong electromagnetic wave absorber

Herein, we developed a three-dimensional composite of reduced graphene oxide (rGO) sheets assembled with flower-like, porous Bi0.9La0.1FeO3 microspheres, using a facile chemical etching process. Their electromagnetic wave absorption properties were investigated. The maximal reflection loss of the composite with the rGO amount of 30 mg reaches −69.97 dB at a thin thickness of 1.91 mm with an effective bandwidth of 5.2 GHz. The composite with 45 mg rGO also exhibits a maximal reflection loss of −58.19 dB at a thinner thickness of only 1.58 mm. The above excellent performances are due to the enhanced conductivity and surface area by the introduction of rGO and the particular microstructure containing abundant surface defects and micro-interfaces, which make it superior to other rGO-based composites reported previously and to be a promising candidate for electromagnetic wave absorber.

Enhanced photoelectrochemical performance of black Si electrode by forming a pn junction

A pn junction based on the black Si wafer has been prepared for the photoelectrochemical (PEC) applications by a facile chemical etching method combined with thermal diffusion process. And also in this work, a black Si wafer were fabricated by using a commercial multicrystaline Si (mc-Si) wafer as the raw. It was demonstrated that pn junction was beneficial to enhance the PEC performance of a Si photoanode. The mechanism was further clarified by an electrochemical impedance analysis. The improved PEC activity was attributed to a more efficient charge separation inside the solid electrode. Besides, the p-type Si wafer displayed a characteristic of n-type semiconductor, which was explained through a simple energy band model.

Template-Directed Growth of Bimetallic Prussian Blue-Analogue Nanosheet Arrays and Their Derived Porous Metal Oxides for Oxygen Evolution Reaction.

Coordination polymers (CPs) are ideal precursors for synthesizing porous catalysts. However, the direct thermolysis of CPs is prone to generate agglomerates, greatly reducing the electrical conductivity and active sites of their derived catalysts. The construction of well-ordered CP nanostructures is a promising strategy for alleviating the above issue, but it remains challenging. Here, a facile chemical etching approach is developed for the fabrication of well-aligned three-dimensional (3D) bimetallic Prussian blue-analogue nanosheet arrays. Impressively, the derived porous metal oxide (Fe-NiO) acts as a remarkable oxygen evolution reaction (OER) catalyst, which merely requires overpotentials as low as 218 and 270 mV to achieve 10 and 100 mA cm-2 in 1.0 m KOH aqueous solution, respectively. The excellent electrocatalytic performance of Fe-NiO is ascribed to the 3D porous nanosheet array architecture, which endows the bimetallic catalyst with abundant electrocatalytic active sites, enhanced surface permeability, and high electronic conductivity. It is expected that the proposed strategy can pave a new way for fabricating highly efficient electrocatalysts for energy storage and conversion.

Effect of inhomogeneous mesoporosity and defects on the luminescent properties of slanted silicon nanowires prepared by facile metal-assisted chemical etching

Slanted silicon nanowires show an improved optical absorption and better electrical contact than the vertical silicon nanowires. High aspect ratio mesoporous slanted silicon nanowires oriented along the ⟨100⟩ direction are fabricated by a facile two-step metal-assisted chemical etching process. Inhomogeneous porosity with a pore diameter of 2–10 nm is identified by the analysis of transmission electron microscopy, angle dependent Raman spectroscopy, and Brunauer-Emmett-Teller measurements. Slanted silicon nanowires possess a core/shell structure, and the porosity varies from top to bottom of the slanted silicon nanowires. The presence of neutral oxygen defects, self-trapped excitons, and surface defects is identified by photoluminescence spectroscopy, and the results are correlated with Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy data. In addition to mesoporosity, defects such as self-trapped excitons, oxygen vacancies, and surface defects on Si/SiOx interface contribute to the luminescence of slanted silicon nanowires. Red shift in the photoluminescence with increasing etching time is explained using quantum confinement luminescent center model. Understanding the role of defects and porosity in slanted silicon nanowires is highly desirable to increase the efficiency of silicon nanowires based optoelectronic devices.

Highly porous Pt-Pb nanostructures as active and ultrastable catalysts for polyhydric alcohol electrooxidations

Highly porous materials have attracted intensive attention in the past decades due to their unique geometrical configuration, unusual structural features, and outstanding physicochemical properties, but the facile creation of porous metal nanomaterias remains a formidable challenge. Most reports focused on using hard templates to create porous metal nanomaterials via sacrificing the templates. Herein, we have created a new class of porous PtPb/Pt nanocrystals (NCs) with well-defined morphology, composition and porosity through a facile chemical etching approach. Due to the highly open three-dimensional (3D) structure and alloy effect, the porous PtPb/Pt NCs exhibit enhanced performances towards polyhydric alcohol electrooxidations with the optimized porous Pt3Pb nanoplates exhibiting superior activities of 1.75 mA cm−2 and 1.19 A mg−1Pt for ethylene glycol oxidation reaction (EGOR) and of 1.46 mA cm−2 and 1.00 A mg−1Pt for glycerol oxidation reaction (GOR) that are much higher than the commercial Pt/C (0.34 mA cm−2 and 0.22 A mg−1Pt for EGOR, 0.30 mA cm−2 and 0.20 A mg−1Pt for GOR). In addition, the porous Pt3Pb nanoplates can endure the long-term stability in EG and glycerol oxidation reactions with limited activity and structure change after 20,000 and 5,000 cycles, respectively, showing a highly promising class of porous Ptbased electrocatalysts for direct polyhydric alcohol fuel cells and beyond.

Constructing flower-like porous Bi0.9La0.1FeO3 microspheres for excellent electromagnetic wave absorption performances

Uniform flower-like porous Bi0.9La0.1FeO3 microspheres etched for 30, 60 and 90 min (named as pBLFO-30, pBLFO-60 and pBLFO-90, respectively) have been successfully constructed by a facile chemical etching process based on Bi0.9La0.1FeO3 particles (BLFO) as precursors. In particular, Sample pBLFO-60 has the largest specific surface area of 75.09 m2 g−1, which leads to the most outstanding electromagnetic wave attenuation performance. The optimal reflection loss (RL) value reaches −57.9 dB when the matching thickness is 2.9 mm at 6.9 GHz and the effective absorption bandwidth (RL < −10 dB) is 2.7 GHz (6.1–8.9 GHz). The three-dimensional porous architecture and enhanced magnetic loss make great contribution to the electromagnetic wave absorption performance, among which the porous microstructure ensures multiple scattering and enhances the magnetic loss contributing to better impedance matching. Meanwhile, the electromagnetic wave absorption performance of porous BLFO microspheres are superior to those of most porous electromagnetic wave absorbers, implying their potential application as novel electromagnetic wave absorbing materials.

Confining Sulfur in Integrated Composite Scaffold with Highly Porous Carbon Fibers/Vanadium Nitride Arrays for High‐Performance Lithium–Sulfur Batteries

AbstractIncreasing the utilization efficiency of sulfur electrodes and suppressing the “shuttle effect” of intermediate polysulfides are the key challenge for high‐performance lithium–sulfur batteries (LSBs). Herein a facile combined strategy is reported to fabricate novel porous carbon fibers/vanadium nitride arrays (PCF/VN) composite scaffold for the storage of sulfur via a facile chemical etching united solvothermal–supercritical fluid method. More active sulfur can be stored in the PCF/VN backbone and dual blocking effects associated with “physical block and chemical absorption” for polysulfides are achieved in the PCF/VN/S integrated electrode. The PCF with highly porous structure provides large space to accommodate active sulfur and possesses cross‐linked maze channels to physically immobilize the polysulfide species. The VN nanobelt arrays demonstrate strong ability for chemically anchoring the polysulfides, thus retarding the shuttle effect. Due to the unique structure and dual confining effect, the designed PCF/VN/S electrode shows a high reversible capacity of 1310.8 mA h g−1 at 0.1 C, an extended cycle life (1052.5 mA h g−1 after 250 cycles) as well as enhanced rate capability, much better than other counterparts (CF/VN/S, PCF/S, and CF/S). This work opens a new door for fabricating high‐performance integrated electrodes for LSBs.

Facile fabrication of superhydrophobic surfaces from austenitic stainless steel (AISI 304) by chemical etching

Stainless steels are among the most common engineering materials and are used extensively in humid areas. Therefore, it is important that these materials must be robust to humidity and corrosion. This paper reports the fabrication of superhydrophobic surfaces from austenitic stainless steel (type AISI 304) using a facile two-step chemical etching method. In the first step, the stainless steel plates were etched in a HF solution, followed by a fluorination process, where they showed a water contact angle (WCA) of 166° and a sliding angle of 5° under the optimal conditions. To further enhance the superhydrophobicity, in the second step, they were dipped in a 0.1 wt.% NaCl solution at 100 °C, where the WCA was increased to 168° and the sliding angle was decreased to ∼2°. The long-term durability of the fabricated superhydrophobic samples for 1 month storage in air and water was investigated. The potential applicability of the fabricated samples was demonstrated by the excellent superhydrophobicity after 1 month. In addition, the self-cleaning properties of the fabricated superhydrophobic surface were also demonstrated. This paper outlines a facile, low-cost and scalable chemical etching method that can be adopted easily for large-scale purposes.

Facile Synthesis of Flowerlike LiFe5O8 Microspheres for Electrochemical Supercapacitors.

Facile synthesis of porous and hollow spinel materials is very urgent due to their extensive applications in the field of energy storage. In present work, flowerlike porous LiFe5O8 microspheres etched for 15, 30, and 45 min (named as p-LFO-15, p-LFO-30, and p-LFO-45, respectively) are successfully synthesized through a facile chemical etching method based on bulk LiFe5O8 (LFO) particles as precursors, and they are applied as electrode materials for high-performance electrochemical capacitors. In particular, the specific surface area of p-LFO-45 reaches 46.13 m2 g-1, which is 112 times greater than that of the unetched counterpart. Therefore, the p-LFO-45 electrode can achieve a higher capacitance of 278 F g-1 at a scan rate of 5 mV s-1 than the unetched counterpart. Furthermore, the p-LFO-45 electrode presents a good cycling stability with 78.3% of capacitive retention after 2000 cycles, which is much higher than that of the unetched LFO particles (66%). Therefore, the flowerlike porous LFO microspheres are very promising candidate materials for supercapacitor applications.

Preparing superhydrophobic copper surfaces with rose petal or lotus leaf property using a simple etching approach

A facile chemical etching process is developed to fabricate superhydrophobic copper surfaces. In the first step, cleaned copper surfaces immersed in ferric chloride (FeCl3) solutions with specific concentrations for different times. Etched surfaces exhibit the maximum contact angle of 140°. They have large sliding angle and water droplets stuck to the surface even if they were turned upside down which is well-known as rose petal effect. After stearic acid modification of etched surfaces, their contact angle slightly increased to above 150° and sliding angle decreased to smaller than 10° in some cases, which is same as lotus plant leaves property against water. Inspecting SEM images of etched surfaces reveals that many micro-nano structures forming blossom like buildings with curved petals of nanoscale thicknesses are formed. The micro-nano structures sizes and shapes affecting surface hydrophobicity are regulated by controlling reaction times and etchant solution concentrations. X-ray diffraction (XRD) analysis is done on a sample before and after of the etching process where patterns indicate that the same compositions present on the sample.

Synthesis and Electrochemical Properties of Coral-Like LiFePO4 Particles as Supercapacitor Electrodes

Facile synthesis of materials with high specific surface areas is very urgent for their potential applications in the field of energy storage. In the present work, coral-like LiFePO4 particles etched for 60, 90, and 120 min (labeled as S-60, S-90, and S-120, respectively) were successfully synthesized through a facile chemical etching method with rugby-like LiFePO4 (named as LFP) particles as precursors synthesized by the solvothermal method. They were then applied as electrode materials for high-performance electrochemical capacitors. In particular, the specific surface area of S-120 reaches 52 m2 g−1, which is 5.2 times greater than that of unetched counterpart. Therefore, S-120 can achieve a higher capacitance of 359 F g−1 at a scan rate of 2 mV s−1 compared with the unetched counterpart. Furthermore, S-120 presents a good cycling stability of 82.3% capacitive retention even after 2000 cycles, which is much higher than that of unetched LFP particles (64%). As a result, the coral-like LFP particles are promising candidate electrode materials for supercapacitor applications.

Real‐Time Probing Nanopore‐in‐Nanogap Plasmonic Coupling Effect on Silver Supercrystals with Surface‐Enhanced Raman Spectroscopy

Nanopore structures have displayed attractive prospects in diverse important applications such as nanopore‐based biosensors and enhanced spectroscopy. However, on the one hand, the fabrication techniques to obtain sub‐10 nm sized nanopores so far is very limited. On the other hand, the electromagnetic enhancement of nanopores is still relatively low. In this work, using a facile chemical etching strategy on 2D plasmonic Ag nanoparticle supercrystals, fine nanopore arrays with sub‐10 nm pore size have been successfully fabricated and a “nanopore‐in‐nanogap” hybrid plasmon mode has been investigated. An in situ etching and surface‐enhanced Raman spectroscopy (SERS) detection indicate that novel hybrid plasmon structure may create an enhanced electromagnetic coupling and increase SERS signal at ≈10× magnification. The breaking of plasmon bonding dipolar mode and generation of antibonding‐like plasmon mode contribute to this enhanced electromagnetic coupling. The facile etching strategy, as a common approach, may open the doors for the fabrication of nanopores in various compositions for numerous applications.

Formation of Prussian-Blue-Analog Nanocages via a Direct Etching Method and their Conversion into Ni-Co-Mixed Oxide for Enhanced Oxygen Evolution.

Novel Ni-Co-Prussian-blue-analog nano-cages consisting of pyramid-like walls were prepared via a facile chemical etching process with ammonia at room temperature. After annealing in air, the derived Ni-Co mixed oxide nanocages exhibit enhanced electrocatalytic activity and excellent stability toward the oxygen-evolution reaction.

Formation of Co3O4 microframes from MOFs with enhanced electrochemical performance for lithium storage and water oxidation.

Co3O4 microframes are synthesized through a template-engaged strategy via the etching of Co-Co Prussian blue analogue microcubes with ammonia solution and subsequent annealing treatment. Benefitting from their unique structural merits including 3D open structure and high porosity, these Co3O4 microframes exhibit enhanced electrochemical properties for both lithium-ion batteries and water oxidation.

Facile synthesis of Ag-coated silicon nanowires as anode materials for high-performance rechargeable lithium battery

Herein, we suggest a facile and cost-effective metal-assisted chemical etching (MACE) method to synthesize uniformly Ag-coated silicon nanowires (SiNWs) using redox reaction, which provides structural and electrical effects on Si negative electrodes at the same time. The combinations of SiNW geometry and Ag nanoparticle (AgNP) coatings are beneficial in preventing pulverization and increasing electrical conductivity of Si negative electrode during cycling, as a result, excellent electrochemical performances are obtained. Transmission electron microscopy (TEM) images reveal that Ag-coated SiNW arrays have been successfully prepared in one-pot MACE process. The electrochemical performances show that the rate capability and cycleability of Ag-coated SiNWs is greatly improved compare to bare NWs. Electrochemical impedance spectroscopy (EIS) measurements show that the electrical conductivity of Ag-coated SiNW electrode is significantly enhanced by Ag coating.

Ag Nanoparticle-Loaded Hierarchical Superamphiphobic Surface on an Al Substrate with Enhanced Anticorrosion and Antibacterial Properties

This paper presents a facile method for preparing Ag nanoparticle (NP)-loaded superamphiphobic surfaces on an Al substrate with efficient anticorrosion and antibacterial properties. A hierarchical steplike microstructure with nanopores is fabricated on an Al surface through facile chemical etching and anodization; subsequent fluorination confers superhydrophobic and superoleophobic properties to this surface. Ag NPs are loaded on the surface nanopores and stabilized by a self-assembled aminopropyltriethoxysilane monolayer through amino-group bonding to prevent aggregation and loss of Ag NPs. Compared with Ag NP-loaded pristine Al substrates, the Ag NP-coated superamphiphobic surface can effectively prevent corrosion of the Al substrate and bacterial absorption, as confirmed by electrochemical impedance spectroscopy, Tafel plot measurement, and bactericidal tests. This study provides novel insights into functional superamphiphobic materials with anticorrosion and antibacterial properties.