Etching In Alkaline Solutions Research Articles

Rapid synthesis of two-dimensional MoB MBene anodes for high-performance sodium-ion batteries

Two-dimensional (2D) transition metal borides (MBenes) have emerged as a rising star and hold great potential promise for catalysis and metal ion batteries owing to a well-defined layered structure and excellent electrical conductivity. Unlike well-studied graphene, perovskite and MXene materials in various fields, the research about MBene is still in its infancy. The inadequate exploration of efficient etching methods impedes their further study. Herein, we put forward an efficient microwave-assisted hydrothermal alkaline solution etching strategy for exfoliating MoAlB MAB phase into 2D MoB MBenes with a well accordion-like structure, which displays a remarkable electrochemical performance in sodium ion batteries (SIBs) with a reversible specific capacity of 196.5 mAh g–1 at the current density of 50 mA g–1, and 138.6 mAh g–1 after 500 cycles at the current density of 0.5 A g–1. The underlying mechanism toward excellent electrochemical performance are revealed by comprehensive theoretical simulations. This work proves that MBene is a competitive candidate as the next generation anode of sodium ion batteries.

Controllable Fabrication of Silicon Solar Cells with Inverted or Upright Pyramid Structures by a One-Step Copper Catalysis Method

Silicon has garnered significant attention as the primary material for solar cell preparation. Traditional alkaline etching solutions are limited to creating an upright pyramid structure on monocrystalline silicon surfaces. However, research indicates that an inverted pyramid structure exhibits superior light-trapping properties compared to the upright pyramid structure. In this study, we employed a one-step copper ion metal-assisted chemical etching process to fabricate an inverted pyramid structure on monocrystalline silicon wafers. This method allows for the customization of either inverted or upright pyramid structures by adjusting the concentration of specific solution components. Characterization of the textured silicon wafers reveals that the inverted pyramid structure exhibits lower reflectivity than both the upright pyramid structure and polished silicon. By integrating this texturing technique into the solar cell production line, we successfully produced solar cells with both inverted and upright pyramid structures. Evaluation of various solar cell parameters demonstrates that the inverted pyramid structure outperforms the upright pyramid structure, showcasing lower reflectivity and higher photoelectric conversion efficiency.

Maskless fabrication of quasi-omnidirectional V-groove solar cells using an alkaline solution-based method

Silicon passivated emitter and rear contact (PERC) solar cells with V-groove texture were fabricated using maskless alkaline solution etching with in-house developed additive. Compared with the traditional pyramid texture, the V-groove texture possesses superior effective minority carrier lifetime, enhanced p–n junction quality and better applied filling factor (FF). In addition, a V-groove texture can greatly reduce the shading area and edge damage of front Ag electrodes when the V-groove direction is parallel to the gridline electrodes. Due to these factors, the V-groove solar cells have a higher efficiency (21.78%) than pyramid solar cells (21.62%). Interestingly, external quantum efficiency (EQE) and reflectance of the V-groove solar cells exhibit a slight decrease when the incident light angle (θ) is increased from 0° to 75°, which confirms the excellent quasi omnidirectionality of the V-groove solar cells. The proposed V-groove solar cell design shows a 2.84% relative enhancement of energy output over traditional pyramid solar cells.

Selective removal of 4H-SiC porous structures caused by photoelectric chemical etching via post oxidation annealing

Low-temperature post oxidation annealing of 4H-SiC at 900 °C for 90 min after photoelectric chemical (PEC) etching in alkaline solution can eliminate the porous structures that form during the etching process, reduce the porosity, and optimize the surface morphology, which has minimal effect on unetched surfaces, allowing for selective treatment between etched and unetched surfaces. Additionally, it can improve the etching depth and enable effective repetition of the etching process. These benefits make PEC etching a valuable technique for microstructure fabrication and surface treatment.

Nanopyramid Texture Formation by One‐Step Ag‐Assisted Solution Process for High‐Efficiency Monocrystalline Si Solar Cells

In monocrystalline Si solar cells, pyramidal surface textures with the size of a few micrometers (micropyramids) are commonly applied for light in‐coupling and trapping. Recently, there is a growing need to reduce the size of pyramids below 1 μm. Herein, an original method to fabricate nanometer‐sized pyramids (nanopyramids) featuring an average size of ≈500 nm or even smaller by using a simple one‐step Ag‐assisted solution process is proposed. The texture size can be controlled by the concentration of AgNO3 in the alkaline etching solution where the generated Ag nanoparticles act as an etching mask as well as promoting the detachment of H2 bubbles from the reacting Si surface. This process enables the formation of uniformly distributed Si nanopyramids with a lower reflectance below 10% and a smaller etching margin less than 1.7 μm compared with the conventional micropyramids. Silicon heterojunction solar cells employing Si nanopyramids outperform those with the conventional micropyramids owing to the reduced optical reflectance while preserving excellent surface passivation and carrier transport properties. These results demonstrate the advantages of our method and the high potential of Si nanopyramids for various applications such as thin crystalline Si solar cells and perovskite/Si tandem solar cells.

Effect of Various Wafer Surface Etching Processes on c-Si Solar Cell Characteristics

In order to analyze the effects of various sizes of pyramid structure on solar cell characteristics, a pyramid structure was formed on the wafer through various etching processes. In this paper, etching was performed using one-step etching processes such as alkaline solution etching, reactive ion etching (RIE), and metal-assisted chemical etching (MACE), and two-step etching processes such as alkaline solution + MACE and alkaline solution + RIE. The micro-sized pyramid-structured wafers formed using the alkali solution showed higher reflectivity than nano-sized pyramid-structured wafers. Accordingly, it was expected that the characteristics of the cells fabricated with a nano-sized pyramid-structured wafer having low reflectivity would be higher than that of a micro-sized pyramid-structured wafer. However, it was confirmed that the quantum efficiency characteristics in the short wavelength region were higher in the micro-sized pyramid-structured wafers than in the nano-sized pyramid-structured wafers. To confirm the reason for this, surface characteristics were analyzed through the deposition of an emitter layer on a wafer formed in a pyramidal structure. As a result, in the case of the nano-sized pyramid-structured wafer, the sheet resistance characteristics were lower due to the increased depth of the emitter layer in comparison to the micro-sized pyramid-structured wafer. Accordingly, it was determined that the quantum efficiency was degraded as a result of the high recombination rate.

Production of hydrogen, active zerovalent iron and ferroferric oxide octahedron by alkaline etching Al–Fe alloys

Hydrogen is becoming important clean energy while zerovalent iron (ZVI) and ferroferric oxide are of great interest to many applications including environmental remediation and chemical catalysis. Here, we report production of hydrogen, zerovalent iron and ferroferric oxide octahedron by etching Al–Fe alloys using NaOH solutions. The rate of hydrogen generation increased with increasing NaOH concentration and the alloy's particle size and decreasing the alloy's Fe concentration. Alkaline etching Al–Fe alloy particles of 425–850 μm produced 19–53 μm ZVI particles, which had paralleled ravines of 0.2–0.3 μm wide on the surface and possessed specific surface areas of 30–70 m2/g. The microscale ZVI was highly active for the removal of a model pollutant acid orange 7 from water. After 3–6 h ageing in the alkaline etching solution, the microscale ZVI particles were transformed to octahedral ferroferric oxide with saturation magnetization of 68.2 emu/g and residual magnetization of 13.2 emu/g and a coercive force of 330 Oe. This study provides a new approach for a facile synthesis of highly active ZVI and octahedral ferroferric oxide along with on-board generation of hydrogen from Al–Fe alloys.

STUDY OF CONDITIONING OF OIL-EMULSION WASTEWATER SEDIMENTS WITH SPENT ALKALINE ETCHING SOLUTIONS OF METALWORKING ENTERPRISES

STUDY OF CONDITIONING OF OIL-EMULSION WASTEWATER SEDIMENTS WITH SPENT ALKALINE ETCHING SOLUTIONS OF METALWORKING ENTERPRISES

A Cellular Automata Based Multi-Process Microfabrication Simulator

We describe a 3D simulator for several fabrication techniques utilized to create MEMS. The software is based on a cellular automata model and allows the user to simulate several processes, such as anisotropic wet etching in alkaline solutions and deep reactive-ion etching (DRIE) on (100) oriented Si substrates. The simulator allows for arbitrarily shaped masking materials and several processes can be applied in sequence to the same substrate. This enables the software to simulate the fabrication of complex MEMS devices which require more than one etching step. So, we show examples of fabrication processes involving different combinations of substrate wet and plasma DRI etching. Although relatively simple automata were utilized for the simulations, the results are in excellent accordance with reported experimental results. At this moment the simulations do not consider physical parameters affecting the fabrication process, the results shown here are important from an engineering point of view for qualitative analyses. At this moment more sophisticated automata are in development to simulate other processes, like film deposition (with different degrees of anisotropy) on previously etched substrates.

The behaviour of AA5754 and AA5052 aluminium alloys in alkaline etching solution: Similarity and difference

In the present study, the behaviour of AA5754 and AA5052 alloys in alkaline solution is investigated using analytical electron microscopy. Significant differences in dissolution rate, change of intermetallic particle population density, compositional and morphological change of various intermetallic particles of the two alloys are observed. The dissolution rate of AA5754 alloy is approximately 1.3 μm/min., which is significantly lower than the dissolution rate of 2.3 μm/min. For AA5052 alloy. After alkaline etching, the population density of coarse intermetallic particles (mainly Mn-rich) on AA5754 alloy surface is significantly reduced whereas the population density of coarse intermetallic particles (mainly Fe-rich) on AA5052 alloy surface remains almost unchanged. Further, the root cause for the different behaviour of the two alloys in alkaline solution is discussed.

Valmet Oyj, Finland

Hydrogen is becoming important clean energy while zerovalent iron (ZVI) and ferroferric oxide are of great interest to many applications including environmental remediation and chemical catalysis. Here, we report production of hydrogen, zerovalent iron and ferroferric oxide octahedron by etching Al–Fe alloys using NaOH solutions. The rate of hydrogen generation increased with increasing NaOH concentration and the alloy's particle size and decreasing the alloy's Fe concentration. Alkaline etching Al–Fe alloy particles of 425–850 μm produced 19–53 μm ZVI particles, which had paralleled ravines of 0.2–0.3 μm wide on the surface and possessed specific surface areas of 30–70 m2/g. The microscale ZVI was highly active for the removal of a model pollutant acid orange 7 from water. After 3–6 h ageing in the alkaline etching solution, the microscale ZVI particles were transformed to octahedral ferroferric oxide with saturation magnetization of 68.2 emu/g and residual magnetization of 13.2 emu/g and a coercive force of 330 Oe. This study provides a new approach for a facile synthesis of highly active ZVI and octahedral ferroferric oxide along with on-board generation of hydrogen from Al–Fe alloys.

Effect of cations on silicon anisotropic etching process in solutions containing TMAH and TMAH with tensioactive compounds

Almost everything has been written on silicon anisotropic etching in alkaline solutions, however, the difference between etching in pure KOH and TMAH as well as in these solutions containing tensioactive compounds has not been completely elucidated yet. This paper present the results of anisotropic etching of Si(100) and Si(110) in the solutions containing two etching agents, KOH and TMAH. Due to this it is possible to control the effect of concentration of each agent on the course of etching and clarify the effect of cation type (inorganic and organic) on the course of the process. The effect of TMA+ ions on etch rate of Si(100) has already been proven both during etching in pure TMAH as well as after addition of tensioactive compounds to this solution. It results in a change in anisotropy ratio (R(110)/R(100)) in TMAH containing solutions in comparison to solutions based on KOH. As the commonly used KOH concentrations (5–10 M) are larger than those of TMAH 25 % (2.7 M), the concentration range of the studied TMAH solution has been extended to 50 %. The paper describes the properties of those concentrated TMAH solutions, both pure and containing surfactants.

Preparation and electrochemical capacitive properties of C–MnO2 composite with foam-like structure based on modified rubber

Nanoporous carbon/MnO2 (C–MnO2) composites with foam-like structure based on modified nitrile butadiene rubber were achieved by thermal treatment, followed by alkaline solution etching and dipping method. The XRD, nitrogen adsorption and desorption, and SEM and TEM were used to characterize the microstructure of the obtained C–SiO2, C and C–MnO2. Finally, all the obtained samples have been used in three-electrode system to study the electrochemical properties including cyclic voltammetry, galvanostatic charge/discharge and AC impedance for supercapacitor. The study found that the specific capacity of C–MnO2 electrode material for supercapacitor could reach as high as 109 F/g under the current density of 0.5 A/g, which is much higher than those of the other two. These superior electrochemical properties are attributed to the synergistic effect MnO2 particles with the C matrix which functions as a conductive support.

Applications of Laser Processing of Materials in Surface Engineering in the Industry 4.0 Stage of the Industrial Revolution

This article presents a comprehensive literature study showing contemporary industrial applications of laser processing of materials in the area of surface engineering. Laser remelting, alloying, feathering, and cladding are discussed. The results of our own research on the application of laser technologies for surface treatment, including hot work tool alloy steels, high-speed steels, magnesium and aluminum alloys, are presented. The production of porous titanium microskeletons prepared using the additive selective laser sintering (SLS) method for the production of original biological engineering materials and implants-scaffolds is presented. The laser texturing of polycrystalline silicon is also presented after texturing requiring etching in alkaline solutions and preferably also after applying antireflective coatings. The article also presents the use of SLS for the application of electrical contacts on photovoltaic cells. Identification of the critical surface of engineering technologies has been presented. Attention was paid to select 21 technologies, which were included in the group of laser processing of materials, from 500 critical technologies of surface engineering that were analyzed with our own methodology of technological foresight. In order to determine the strategic position of individual groups of critical technologies, an original set of context matrices was developed, including the dendrological matrix of technology values and the meteorological matrix of environmental impact, and the results were summarized in a sixteen-field strategy matrix for technologies. A 20-year time horizon of heuristic research was established. It has been shown that the analyzed technologies of laser processing of materials are finding wider and wider application in modern technology so that their significant development in the next two decades should be expected. It has been pointed out that laser surface technologies, because of their high development potential demonstrated by the performed foresight research, are some of the important elements of the development of the Industry 4.0 idea.

Pyramid‐Textured Antireflective Silicon Surface In Graphene Oxide/Single‐Wall Carbon Nanotube–Silicon Heterojunction Solar Cells

Antireflection layers are commonly used in photovoltaics to increase light absorption and therefore increase maximum photocurrent. Here, pyramid structures are created on Si surfaces with alkaline solution etching. The extent of pyramid coverage depends directly on the reaction time and as a result, the surface reflectance decreases with reaction time. A floating transfer method is used to fabricate heterojunction solar cells based on graphene oxide‐carbon nanotube and Si heterojunctions. The best device performance (photo current conversion efficiency of 13.01 ± 0.32%, which is much higher than the efficiency of the control devices (10.18 ± 0.33%)) was observed using with cells fabricated with the highest coverage (99.9%) of pyramids on the Si surfaces, which is determined to be a combined effect of reduced surface reflectance and increased effective heterojunction area per unit active area.

Practical Aspects of Pretreatment of Aluminum Surfaces for Industrial Anodizing

The most widely adopted techniques for etching aluminum surfaces for industrial anodizing are described. The processes involved in the dissolution of surface layers of aluminum in acidic and alkaline media are described in terms of their economic and ecological viability and practical use. The advantages of using composite alkaline etching solutions are demonstrated.

Passivation of textured crystalline silicon surfaces by catalytic CVD silicon nitride films and catalytic phosphorus doping

Silicon nitride (SiNx) films formed by catalytic chemical vapor deposition (Cat-CVD) and phosphorus (P)-doped layers formed by catalytic impurity doping (Cat-doping) are applied for the passivation of pyramid-shaped textured crystalline Si (c-Si) surfaces formed by anisotropic etching in alkaline solution. Lower surface recombination velocities (SRVs) tend to be obtained when smaller pyramids are formed on c-Si surfaces. P Cat-doping is effective for reducing the SRV of textured c-Si surfaces as in the case of flat c-Si surfaces. We realize SRVs of textured c-Si surfaces of ∼8.0 and ∼6.7 cm/s for only SiNx passivation and for the combination of SiNx and P Cat-doping, respectively. These structures also have high optical transparency and low Auger recombination loss, and are of great worth in application for the surface passivation of interdigitated back-contact c-Si solar cells.

Rapid reagent-less on-line H2O2 quantification in alkaline semiconductor etching solution

A simple, rapid, and reagent-less calorimetric method for H2O2 quantification, applicable automatically on-line was developed, analytically characterized and tested with real SC-1 alkaline etching solutions used in the semiconductor technology. Being based on H2O2 catalytic decomposition by immobilized solid catalyst, the proposed method possesses excellent specificity toward the H2O2 without any interference. The total quantification time was found to be less than 60s, RSD lies in the range from 4.7% to 1.8% for the linear concentration range from 2.8 10−2 to 2molL−1 respectively and the LOD was determined to be as low as 9.3 10−3molL−1.

Petal shaped nanostructures planted on array micro-patterns for superhydrophobicity and anti-icing applications

The aim of this paper is to report a facile strategy of planting a layer of petal shaped nanostructures on the surface of array micro-patterns, and producing the excellent superhydrophobicity and anti-icing property. In this work, the superhydrophobic surfaces were prepared by modifying petal shaped nanostructures (constructed by chemical etching in alkaline solution) planted on array micro-patterns (constructed by lithography process with the electrochemical etching under the neutral solution condition) on aluminum substrate with fluoroalkylsilane (FAS-17). Meanwhile, we further studied the effects of chemical etching process parameters on morphology and superhydrophobicity, and on this basis explored the anti-icing potential under the condition of icing wind tunnel. The results indicated that the process parameters including NaOH concentration of 0.05M, etching time of 5min, and the subsequent boiling time of 40min were of benefit to producing the ideal nanostructure morphology and geometric dimension, and the resultant surface displayed an excellent superhydrophobicity with the apparent contact angle of 165° and the sliding angle being almost equal to zero (cannot be measured). Furthermore, the as-superhydrophobic surface generated a tremendous anti-icing potential, greatly preventing the icing accumulation at −10°C under the condition of icing wind tunnel, and exhibiting a lower ice adhesion strength comparing with a market mature production of superhydrophobic coating.

Fe3O4/Ag microsheets assembled by interlaced nanothorns as high performance anode materials for lithium storage

Fe3O4/Ag nanocomposite is directly prepared by dealloying a well-designed FeAgAl source alloy in alkaline etching solution at room temperature. Selectively dissolving Al from FeAgAl alloy results in Fe3O4/Ag microsheets assembled by second order interlaced nanothorns. On account of the distinctive hierarchical micro-/nano-structure and the hybridization of well conductive Ag, Fe3O4/Ag composite shows much improved lithium storage performances with higher capacities, cycling stability, and coulombic efficiency compared with the pure Fe3O4 anode. Even the current rate is as high as 1 A g−1, the capacity of Fe3O4/Ag composite still exceeds 600 mA h g−1 after cycling 500 cycles compared with the remained value of only 294.8 mA h g−1 for pure Fe3O4. Moreover, Fe3O4/Ag composite presents the excellent rate capabilities at whether low or high current densities. Owing to the superiorities of excellent properties and handy preparation, the Fe3O4/Ag anode exhibits encouraging prospect for lithium ion batteries.