Etching Time Research Articles

Study of the Dissolution of Tahoua Natural Phosphate by Mineral Acids: Hydrochloric Acid and Sulfuric Acid

The transformation of natural phosphorus into plant nutrient phosphorus, natural phosphates from Tahoua were dissolved in mineral acids, hydrochloric acid and sulfuric acid. Dissolution was effected at various concentrations (0.01M; 0.1M and 1M) and stirring times (1 hour, 3 hours and 5 hours). The results show that for all two acids (2), the dissolution rate is greater in concentrated acid solutions (1M) and for the 5-hour attack time. These rates are 38.37% and 34.87% respectively for sulfuric and hydrochloric acid solutions. Dissolution of Tahoua natural phosphate depends on the concentration of etching solutions and the etching time. With mineral acids (sulfuric and hydrochloric acid), for example, it increases with concentration. This dissolution offers interesting visions for perfecting phosphate fertilizers.

Vertical silicon nanowedge formation by repetitive dry and wet anisotropic etching combined with 3D self-aligned sidewall nanopatterning

Three-dimensional (3D) stacking of nano-devices is an effective method for increasing areal density, especially as downscaling of lateral device dimensions becomes impractical. This stacking is mainly achieved through plasma processing of stacked layers on top of a silicon (Si) substrate, which offers process flexibility but poses challenges in obtaining vertical sidewalls without plasma induced damage. A novel wafer-scale fabrication method is presented for realizing sub-200 nm vertically stacked Si nanowedges at the wafer scale, using iterative dry etching, wet anisotropic etching, and thermal oxidation. This approach forms nanowedges by the slow etching {111} Si planes, resulting in smooth surfaces at well-defined angles. A silicon nitride (Si3N4) hard mask is used in an iterative (etch-and-deposit) process, with its thickness determining the number of process iterations. By optimizing etch selectivity during dry etching and/or increasing the initial Si3N4 thickness, the number of process iterations can be increased. The periodicity of the nanowedges can be adjusted by varying the etch time of both dry and wet anisotropic etching. A thin silicon dioxide (SiO2) layer (∼6 nm) is grown on the nanowedges during each iteration. 3D sidewall patterning at the sub-20 nm scale is achieved using corner lithography and local oxidation of Si to selectively open the concave corners. Rhombus-shaped structures are formed at each concave corner after wet anisotropic etching of Si. This novel technology platform will allow for the 3D fabrication of high-density nanodevices for electronic, fluidic, plasmonic, and other applications.

Pomegranate-like cobalt Phosphides@P-Doped carbon Nanostructures with controlled phase as anode materials for Lithium-Ion batteries

Transition metal phosphides (TMPs) have recently emerged as prominent energy conversion and storage materials owing to their unique physicochemical property. Nevertheless, it’s still a difficult task to obtain phase-control of TMPs owing to multiple energetically favorable stoichiometries. Herein, a phase-controllable cobalt phosphide@C with the pomegranate core–shell structure are successfully realized by employing Co-glycerate as precursors and phytic acid (PA) as P sources, etching and coordination agents. With the presence of six phosphoryl groups and the strong coordination ability, PA allows the self-phosphating of Co atoms and the P-doped carbon shell, as well as the confinement of the obtained nanoparticles Additionally, as an organic acid, PA can etch the Co-glycerate precursors with the formation of hollow structures. With different etching time, metal-rich phosphides Co2P@C and monophosphides CoP@C are successfully achieved. When applied as anode materials, CoP@C demonstrates superior lithium storage performance by delivering a prominent reversible capacity up to 1187 mAh/g at 0.1 A/g and shows no capacity loss at 1 A/g after 500 cycles. This work presents a simple protocol to obtain TMPs with tunable metal/phosphorus ratios, phase selectivity and interface engineering, which could be applied in the field of energy storage and electrocatalysis.

Improvement of porous silicon by adding CIGS NPs prepared by laser ablation method in water

Using a laser energy of no more than 600 mJ/pulse and a maximum of 500 pulses, this work selectively produced pure copper, indium, gallium, and selenide (CIGS) NPs using a laser ablation method with distilled water and n-type porous silicon prepared by the photoelectron etching method. The material exhibits quantum dot behavior, according to experimental investigations. Porous silicone bases were produced using a current density of 10 mA/cm2 and an etching time of 15 min. Tests XRD, SEM, AFM, FTIR, UV, PL were conducted for the porous silicone and CIGS NPs to ensure that each of them is produced efficiently. To produce a hybrid junction\CIGS\Psi\n-Si\AG we see an enhancement of the spectral response of 0.71 A/W when a quantum dot is deposited on porous silicon.

Effect of Alkaline Etching on Formation Behavior and Corrosion Resistance of a Cr-Zr-Ti TCP Conversion Coating on AA2024 Aluminum Alloy

Abstract Trivalent chromium process conversion coating is considered to be the ideal alternative to traditional chromate conversion coating due to its high corrosion resistance and low toxicity. However, achieving a high corrosion resistance trivalent chromium conversion coating on 2xxx aluminum alloys has been a great challenge. Herein, based on a newly developed trivalent chromium conversion solution (CN patent, ZL 202210804263.2), the effect of alkaline etching on the formation behavior and corrosion resistance of the coating on AA2024-T351 aluminum alloy was investigated. It was found that under the same conditions, the mechanically polished sample and the sample alkaline etched for 30 s showed the highest corrosion resistance. When the alkaline etching time was too short or too long, the corrosion resistance of the coating deteriorated. This is ascribed to changes in the surface microstructure of the alloy during alkaline etching, i.e., reduced number of intermetallic particles and formation of a copper enrichment layer. Reducing the number of intermetallic particles on the alloy surface is beneficial for uniform growth of the coating. However, the copper enrichment layer participated in formation of the coating, resulting in doping of copper species in the coating, which is detrimental to the corrosion resistance of the coating.

Acid-etching protocol for bioceramic cements: Evaluation of bond strength, compression and morphology.

To establish an acid-etching protocol for Biodentine and Cimmo DTA, evaluating compressive strength, bond strength, surface morphology in scanning electron microscope and failure modes after different etching times. Two test specimens were prepared for each cement and divided into four groups (n = 12) according to the acid-etching time (0, 5, 10 and 15 s). Compressive strength was tested using a universal testing machine, while bond strength was evaluated after bonding with Filtek Bulk Flow resin using Universal ESPE Single Bond adhesive. Failures were classified as surface-adhesive, cement-cohesive, resin-cohesive and mixed. Biodentine showed significantly higher compressive strength than Cimmo DTA (p < 0.001), regardless of acid etch time (p < 0.001). Different acid-etching strategies are required for Biodentine and Cimmo DTA, with Biodentine requiring selective etching and Cimmo DTA requiring a full 15-s etch to optimise bond strength properties.

Research on wafer-level SiC microgroove array process via integrated molding-etching process

Silicon carbide (SiC) microgroove arrays (MGAs) play a pivotal role as optical components in modern optical engineering. This paper introduces an innovative approach for the fabrication of MGAs on hard materials. This method integrates hot embossing (HE) and inductively coupled plasma (ICP), utilizing polydimethylsiloxane (PDMS) as the intermediary mold due to its excellent demolding performance and shape replication qualities. The process involves transferring the MGAs from the Ni-P master mold to the PDMS mold, followed by replication onto the photoresist surface by hot embossing. Subsequently, the MGAs on the photoresist mask is etched into the hard substrate material using ICP etching. For efficient customization of MGAs, a reliable geometrical model based on angular dependence theory is developed to assist in selecting process parameters and designing masks. The correlation between etching selectivity and characteristic dimension is elucidated. Experimental results demonstrate that the sidewall angle decreases with higher selectivity and increases with a greater sidewall angle on the patterned mask. Plasma etching reveals unaffected areas in convex corners and the forming errors in concave corners, highlighting a high angular dependence of the etch rate. Moreover, minimizing microdefects can be achieved by optimizing process parameters and reducing etch time.

Aging damage characteristics of acid‐etched sandstone samples

AbstractTo investigate the erosive damage effect of the acidic solution on sandstone, experiments were conducted to examine the macro‐ and micro‐characteristics of sandstone samples under different acid etching times. Microscopic morphology changes, pore structure characteristics, mineral composition changes, and mechanical response characteristics were obtained before and after acid etching. Finally, a comprehensive evaluation index for acid etching damage was proposed. The results show that: (1) Acidic solution will erode the sandstone skeleton and cause the sandstone to collapse. The etched surface appears “flocculent” and yellow sediment is produced. (2) The pores in sandstone samples are mainly micro‐ and mesopores, and the total porosity increases exponentially with the duration of acid etching. The volume fraction of micropores can reach up to 81.5%. (3) The acid etching process of sandstone samples includes physical diffusion and chemical dissolution, which can be divided into four stages and three regions from the outside to the inside. After acid etching, the uniaxial compression failure mode of the sample changes from shear to mixed shear‐tensile failure. (4) The comprehensive evaluation index based on three failure modes generated during the loading process shows good consistency with the overall changes of characteristics parameters such as elastic modulus, peak stress, and peak strain. The research findings of this paper can provide theoretical support for the assessment of rock mass stability and disaster prevention in acidic environments.

Synthesis of fluorine-free Ti3C2Tx MXenes via acidic activation for enhanced electrochemical applications

MXenes are a class of two-dimensional materials composed of carbides and nitrides, which possess tunable properties and thus suitable for electrochemical applications. The etching method of MXene plays an important role in defining the electrochemical properties. Here, a novel hydrothermal acidic etching process was introduced to synthesize fluorine free MXenes by varying etching time and temperature. As a result, highly effective fluorine free Ti3C2Tx MXenes with enhanced electrochemical properties were obtained. It is also noted that the synthesized Ti3C2Tx MXenes exhibit distinct charge-discharge performance and impressive battery-like characteristics when tested in a 1 M H2SO4 electrolyte. Especially, the 6D-160 °C sample shows relatively superior gravimetric capacity of 450 C g−1 with a retention rate of 114 % after 8000 cycles, compared to the HF-etched sample (only 75 % lower capacitance). This novel approach demonstrates a significant improvement in the electrochemical performance of Ti3C2Tx MXenes and suggests a highly effective technique for surface modification of MXenes.

Deep cryogenic silicon etching for 3D integrated capacitors: A numerical perspective

One promising approach to increase the capacity density of integral microcapacitors, microsupercapacitors, and microbatteries is three-dimensional structure design, where electrodes are exposed in three dimensions instead of conventional in-plane electrodes. Such structures include nanowires, nanotubes, nanopillars, nanoholes, nanosheets, and nanowalls. In this work, a cryogenic silicon etching process suitable for fabrication of structures with high electrode area is proposed. A numeric model of this process is experimentally calibrated and used for pillar array structure sidewall area optimization. The use of adaptive Runge–Kutta–Fehlberg time integrator allows to achieve almost linear overall computation complexity as a function of simulated etching time, despite the linear increase in conductance computation complexity with depth. A rule for choosing optimal geometric structure parameters under technological constraints is formulated. An optimized trefoil-like structure is proposed, resulting in a total 5.5% increase in sidewall area with respect to the hexagonal array of circular pillars, resulting in 20.33 sidewall area per unit chip area for 30 min long etch or 31.80 for 60 min long etch.

Investigating the effect of Cu underlayer and FTO etching towards photoelectrochemical performance enhancement of Cu2O photoelectrode

Cuprous oxide (Cu2O) exhibits potential as a photoactive material for photoelectrochemical water splitting, owing to its appropriate bandgap, efficient charge carrier separation, and ability to enhance solar-driven hydrogen production. This study investigates the influence of substrate etching, Cu underlayer and Cu2O electrodeposition time, and annealing time on enhancing the photoelectrochemical (PEC) performance. Electrodeposition and thermal oxidation techniques were used to fabricate the Cu2O/Cu/FTOe-A photocathode. It has been observed that FTO etching improves adhesion, light transmission, and efficiency. A Cu underlayer also impacts the PEC performance, wherein an ideal thickness of Cu leads to enhanced PEC performance. This study also focuses on the annealing time that leads to CuO layers and nanowires forming on the Cu2O surface. The structural and chemical changes before and after annealing are confirmed via XRD, XPS, AFM and FESEM analyses. UV–Vis analysis also reveals that the presence of Cu underlayer, FTO etching, and the annealing process affect the electrical properties and light absorption capacities of the Cu2O photoelectrode. Electrochemical impedance analysis (EIS) and Mott-Schottky analysis have provided insights into the enhanced charge transfer properties and band bending in the Cu2O/Cu/FTOe-A, resulting in enhanced PEC performance. Overall, this study provides significant insights into the understanding and enhancement of Cu2O/Cu/FTOe-A photocathodes for potential use in PEC water splitting applications.

Hyperspectral Analysis of Silicon Nanowires Manufactured Through Metal-Assisted Chemical Etching

Abstract This study used hyperspectral imaging to analyze localized near-field interactions between incident electromagnetic waves and silicon nanowire (SiNW) arrays manufactured through catalytic etching of Si wafers for different durations. The results revealed that the unetched upper surface area on Si wafers and reflection of incident light decreased with increasing etching time. A light reflection band peaking at approximately 880 nm was generated from arrays etched for more than 1 h. We used six separate hyperspectral images to analyze the wavelength-dependent spatial optical responses of the fabricated SiNW arrays. The images revealed hot spots of light reflection from unetched Si surfaces in the wavelength range of 470–750 nm and a resonant peak at 880 nm for a photonic crystal derived from a random SiNW array. Accordingly, hyperspectral imaging enables the assessment of localized optical responses of SiNW arrays, which can then be optimized to cater to various applications.

Effects of chemical etching on surface structure and tribological behavior of silicate substrates

Abstract This study investigated the effect of chemical etching on the surface structure and tribological behavior of silicate substrates. Silicate surfaces were etched using a mixture of nitric acid (HNO3) and ammonium bifluoride (NH4HF2) for durations ranging from 1 to 60 min. The etched surfaces were characterized using optical microscopy, scanning electron microscopy, surface profilometry, water contact angle measurements, and UV–vis spectroscopy to evaluate the changes in surface morphology, roughness, wettability, and optical properties. Tribological performance was assessed using reciprocating ball-on-plate friction tests. The results showed that increasing the etching time resulted in the formation of microscale surface features, increased surface roughness, enhanced hydrophilicity, and reduced optical transmittance. The average friction coefficient decreased with an increase in the etching time up to 30 min, beyond which a slight increase was observed. The 1-minute etched specimen exhibited the best wear resistance with the narrowest wear track and the least material removal. The improved tribological performance was attributed to the formation of a stable transfer film, reduced real contact area, and entrapment of wear debris. This study highlights the potential of chemical etching as a technique to tailor the surface structure and tribological properties of silicate materials for various applications.

Sampling Confined Fission Tracks for Constraining Geological Thermal Histories

Fission-track modeling rests on etching, counting and measuring the lattice damage trails from uranium fission. The tools for interpreting fission-track data are advanced but the results are never better than the data. Confined-track samples must be an adequate size for statistical analysis, representative of the track population and consistent with the model assumptions and with the calibration data. Geometrical and measurement biases are understood and can be dealt with up to a point. However, the interrelated issues of etching protocol and track selection are more difficult to untangle. Our investigation favors a two-step protocol. The duration of the first step is inversely proportional to the apatite etch rate so that different apatites etch to the same Dpar. A long immersion reveals many more confined tracks, terminated by basal and prism faces. This allows consistent length measurements and permits orienting each track relative to the c-axis. Long immersion times combined with deep ion irradiation reveal confined tracks deep inside the grains. Provided it is long enough, the precise immersion time is not important if the effective etch times of the selected tracks are calculated from their measured widths. Then, whether the sample is mono- or multi-compositional, we can, post hoc, select tracks with the desired properties. The second part of the protocol has to do with the fact that fossil tracks in geological samples appear to be under-etched compared to induced tracks etched under the same conditions. This should be assumed if the semi-axes of a fitted ellipse plot above the induced-track line. In that case, an additional etch can increase the track lengths to a point where they are consistent with the model based on lab-annealing of induced tracks, a condition for valid thermal histories. Here too, it is possible to select a subset of tracks with effective etch times consistent with the model if the widths of confined tracks are measured along with their lengths and orientations.

Nanochannels in Fused Silica through NaOH Etching Assisted by Femtosecond Laser Irradiation

Sodium hydroxide (NaOH) is increasingly drawing attention as a highly selective etchant for femtosecond laser-modified fused silica. Unprecedented etching contrasts between the irradiated and pristine areas have enabled the fabrication of hollow, high-aspect-ratio structures in the bulk of the material, overcoming the micrometer threshold as the minimum feature size. In this work, we systematically study the effect of NaOH solutions under different etching conditions (etchant concentration, temperature, and etching time) on the tracks created by tightly focused femtosecond laser pulses to assess the best practices for the fabrication of hollow nanostructures in bulk fused silica.

Errors in the field reconstruction using CR-39 proton radiographs with high fluence variation.

CR-39 proton radiography is an experimental charged-particle backlighter platform fielded and used at OMEGA and the NIF to image electric and magnetic fields in a subject plasma. Processing a piece of CR-39 involves etching it in hot NaOH, and the etch time can greatly impact the background-to-signal ratio (BSR) in low-fluence (≲4 × 104cm-2) regions and detection efficiency in high-fluence regions (≳7 × 105cm-2). For CR-39 data with high fluence variation, these effects mean that any single etch time will result in ≳15% error in the measured signal in either the high- or low-fluence regions. This study aims to quantify the impact of the etch time on the BSR and efficiency losses and how these affect the field reconstruction. Experiments at the MIT Linear Electrostatic Ion Accelerator provided empirical values of the BSR and efficiency losses as a function of the fluence and etch time for fluences ranging from 3 × 103 to 7 × 105cm-2. Synthetic radiographs were generated with known fields and modulated based on empirical values of BSR and efficiency losses. The fields were reconstructed using a Monge-Ampère code with the modulated radiographs as input. The results indicate that combining short and long etches allows for more accurate analysis of radiographs with high fluence variation, with the mean squared error of the reconstructed fields decreasing by factors of 1.2-7 compared to the reconstructions using only one etch time.

Quantifying the effects of neutron fluence on proton signal retention in CR-39.

This paper reports on investigations on the impact of higher neutron fluences on the detection efficiency of protons with CR-39, a charged particle track detector. CR-39 is widely used as a diagnostic for inertial fusion applications and is an integral component of numerous particle diagnostics at the OMEGA laser facility and National Ignition Facility. As experiments continue to produce higher and higher yields, existing diagnostics are impacted by higher particle fluences than they were originally designed for. This paper presents data from experiments measuring proton signal on pieces of CR-39 with different levels of neutron fluence with two different etch times. The experiments show a decrease in signal recovery with increased neutron fluence, which is exacerbated at longer etch times. At 3h etch time, data suggest a 17% ± 7% signal loss at 1.3 × 105 neutron-induced tracks per cm2 and a 67% ± 21% loss at 6h etch time. Careful signal isolation techniques can recover most of the proton tracks even with moderate neutron fluence.

Ammonia Gas Sensing Using Porous silicon

Abstract Psi prepared by Electrochemical etching technique at invariable etching current density of 10 mA/cm2 and at different times (7 and 17) min. The porous Si structure was studied using XRD, (FE-SEM) and EDS. The process of sensing NH3 gas is carried out at different operating temperatures (R.t,80,130 and 200)°C and the gas concentration is constant. It is measured by changing the resistance of the sensor as a function of exposure time to the gas. The result showed the XRD patterns of the PS at (7 and 17) min etching time. the peak samples at (111) around 2θ = 28.5°. It is observed that the peak intensity declines with rising the etching time, and some structural parameters for porous silicon are calculated. From FE-SEM, the images show the sample prepared in (7 and 17) min with the depth of (6.18 12.82) μm, with a size of about 50 nm. Porous silicon that was produced in a time of 17 min has a higher sensitivity to NH3 gas than that of the sample that was produced in a time of 7 min. It was found that when the operating temperature changes from (R.T -200C°), the sensitivity of the samples changes with the stability of the etching time. The PSi sample (17 min) has a high sensitivity for NH3 gas at room temp.

A facile nanopattern modification of silk fibroin electrospun scaffold and corresponding impact on cell proliferation and osteogenesis

Abstract As a well-known natural protein biomaterial, silk fibroin (SF) has shown broad application prospects in typical biomedical fields. However, the mostly used SF from Bombyx mori silkworm lacks specific cell adhesion sites and other bioactive peptide sequences, and there is still significant room for further improvement of their biological functions. Therefore, it is crucial to develop a facile and effective modification strategy for this widely researched biomaterial. In this study, the SF electrospun scaffold has been chosen as a typical SF biomaterial, and air plasma etching has been adopted as a facile nanopattern modification strategy to promote its biological functions. Results demonstrated that the plasma etching could feasibly and effectively create nano-island-like patterns on the complex surface of SF scaffolds, and the detailed nanopattern features could be easily regulated by adjusting the etching time. In addition, the mesenchymal stem cell responses have illustrated that the nanopattern modification could significantly regulate corresponding cell behaviors. Compared with the non-etched scaffold, the 10 min-etched scaffold (10E scaffold) significantly promoted stem cell proliferation and osteogenic differentiation. Moreover, 10E scaffold has also been confirmed to effectively accelerate vascularization and ectopic osteogenesis in vivo using a rat subcutaneous implantation model. However, the mentioned promoting effects would be weakened or even counteracted with the increase of etching time. In conclusion, this facile modification strategy demonstrated great application potential for promoting cell proliferation and differentiation. Thus, it provided useful guidance to develop excellent SF-based scaffolds suitable for bone and other tissue engineering.

β-Ca3(PO4)2- Ca9.95Li1.05(PO4)7 lamellar microstructure by chemical etching: Synthesis, characterization and in vitro bioactivity

In this study, new multilayer 3D porous scaffolds were designed with a core composed of Ca3O5Si (C3S) and external layers composed of Ca5Li2(PO4)4. Scaffolds' surface topography was modified to reveal a lamellar microstructure by applying chemical etching. Scaffolds were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy with Energy Dispersive X-ray spectroscopy (FESEM/EDX), Fourier Transform Infrared Spectroscopy (FTIR) and Mercury Porosimetry. In vitro bioactivity was evaluated by immersing scaffolds in simulated body fluid (SBF) at 1, 3 and 7 days. Scaffolds presented calcium pyrophosphate, β-tricalcium phosphate (β-TCP), nonstoichiometric and stoichiometric calcium/lithium phosphate as the main phases. The calcium pyrophosphate and stoichiometric calcium/lithium phosphate in the external layer were eliminated by the chemical etching process, which revealed the lamellar microstructure. Lamellar width varied from 1.44 μm to 0.73 μm depending on the chemical etching time. The obtained mechanical strength results influenced samples’ macroporosity, which ranged from 50 % to 64 %. These samples also exhibited microporosity between 30.3 % and 49.0 %. During the bioactivity test, all the chemically etched samples showed a hydroxyapatite-like (HA-like) precipitate, except for the sample chemically etched for 30 s at day 1. At day 7, the lamellar microstructure in the samples chemically etched for 30 s and 45 s (C-30 s and C-45 s) was completely covered by the HA-like precipitate, whereas the lamellar microstructure in the sample chemically etched for 60 s (C-60 s) was only partially covered by the HA-like precipitate.