Electrolytic Etching Research Articles

Investigation of the response of thin CR-39 polymer foils irradiated with light ions

One of the most often used polymer for radiation research and protection dosimetry is poly[diethylene glycol bis-(allyl carbonate)] which is commercially named CR-39. Due to a unique sensitivity it is the most suitable material for low-energy light ions studies. In this work the track breakthrough is studied by using an effective method of electrolytic etching, which was earlier successfully applied to swift heavy ions in several polymers. Samples of CR-39 with the thickness of 22–400μm were irradiated with protons and helium ions having energies up to 7MeV/amu. Using the conductivity data, sequent openings of the pores were observed. Moreover, with the help of electron scanning microscopy, a model of pore formation was constructed and the influence of energy losses on the geometry of tracks as well as the rate of the process were investigated. Finally, the latent track size was obtained from the experimental data and compared with that of other ions.

Proton tracks and the formation of pores in poly[diethylene glycol bis-(allyl carbonate)

Modern dosimetry needs efficient detectors for registering light ions, especially light ions having energies of up to 10 MeV/amu. That is why this research pays attention to the development of materials for such a task. In this work, a CR-39 detector, which is the most efficient detector, was used. It was irradiated with low-energy protons. Using sensitive electrolytic etching and electron scanning microscopy, a complete analysis was carried out of the process of the formation of a pore starting from its opening to the final stage of its formation. The process of sequential track breakthroughs was observed. The data obtained on the shape of the pore and the parameters of its formation allow simulation of the process of etching. The etch rates and sensitivity of etching are determined. The influence of energy losses on the geometry of the pore is considered.

Stand-alone device for the electrolytic fabrication of scanning near-field optical microscopy aperture probes

Near-field optical applications require the fast, stable, and reproducible fabrication of scanning near-field optical microscopy (SNOM) aperture probes in the submicrometer range. We have developed a stand-alone device for the electrolytic etching of nanoapertures with an integrated current and optical transmission monitoring and control. Probes with an aperture ranging from 50to100nm were reproducibly fabricated with great reliability. With these probes, high resolution SNOM images of 100nm test patterns and single dye molecules (Rhodamine 6G in poly(vinyl alcohol)) are measured and presented. Not requiring a SNOM setup, the stand-alone device is not only inexpensive and compact, but also insensitive to external disturbances.

Fabrication and morphology of porous p-type SiC

Porous silicon carbide fabricated from p-type 4H and 6H SiC wafers by electrochemical etching in hydrofluoric electrolyte is studied. An investigation of the dependence on wafer polarity reveals that pore formation is favored on the C face while complete dissolution occurs on the Si face. When the etching is done on the C face, the pore wall thickness decreases with increasing current density. The morphology of the front surface of the sample depends on the prior treatment of the workpiece surface. The porosity is estimated based on the analysis of scanning electron microscope images, charge-transfer calculations, and gravimetric analysis.

Wet etching of GaN, AlN, and SiC: a review

Abstract The wet etching of GaN, AlN, and SiC is reviewed including conventional etching in aqueous solutions, electrochemical etching in electrolytes and defect-selective chemical etching in molten salts. The mechanism of each etching process is discussed. Etching parameters leading to highly anisotropic etching, dopant-type/bandgap selective etching, defect-selective etching, as well as isotropic etching are discussed. The etch pit shapes and their origins are discussed. The applications of wet etching techniques to characterize crystal polarity and defect density/distribution are reviewed. Additional applications of wet etching for device fabrication, such as producing crystallographic etch profiles, are also reviewed.

Nanoscale GaN whiskers fabricated by photoelectrochemical etching

GaN whiskers with nanoscale dimensions have been fabricated by photoelectrochemical (PEC) etching in dilute H3PO4 electrolyte. Etching in lower concentration H3PO4 electrolyte for 1 h or for a short time of 5 min at a higher concentration results in individual whiskers with a density of ∼2×109cm−2 and diameters to 15nm. It is observed that ∼10% of them have formed nearly perfect hexagonal plates on the top of the whiskers, which appear to evolve into flowerlike features upon extended etching to 12 min. Such hexagonal plates have not been reported previously in the PEC etching of GaN. The presence of a dislocation along the central axis of the needles is clearly demonstrated, and the etch pattern is suggested to be related to the growth mechanism for GaN on sapphire. When etched for times >30min, these whiskers are typically arranged in clusters with a density of 2–5×107cm−2 and have ten or more whiskers contributing to the central top of the cluster.

Secondary austenite and chromium nitride precipitation in simulated heat affected zones of duplex stainless steels

Primary and secondary intragranular austenite precipitation and its relationship with chromium nitride (Cr2N) were studied in a simulated multipass heat affected zone (HAZ) of five duplex stainless steel alloys (UNS S32304, S32205, S32550, S32750, and S32760). The Gleeble thermal-mechanical simulator was used to perform short duration and high cooling rate ferritisation and reheating heat treatments. TEM and FEG-SEM analysis, coupled with a specially developed electrolytic etching technique, revealed the cooperative growth of secondary austenite and Cr2N precipitation along the ferrite/austenite (α/γ) interfaces. Additionally, the observed close coexistence of intragranular nitride (Cr2N) and intragranular secondary austenite suggests the heterogeneous nucleation of secondary austenite from the nitrides as supported by previously reported low energy nitride/austenite (Cr2N/γ) interfaces for the observed orientation relationship between both phases. Based on these observations, a new mechanism is proposed for intragranular secondary austenite nucleation related to the intragranular nitride precipitates.

A Study on On-machine Resharpening of Cutting Tools (The Process Development Employing Composite Electroplating and Electrolysis)

This study deals with on-machine resharpening of cutting tools for the purpose of reducing the consumption of scarce materials and suppressing the total production time on precision machining. To make the resharpening processes on machine automatically, the processes must he fast and its apparatus must be simple. So the conventional methods like grinding or PVD coating can't meet the requirements. Electrodeposition of composite coating is one of the methods which meet the requirements. Ni-P-SiC composite coating layer on cemented carbide tool was able to cut steel. Then, by electrolytic etching with H2SO4 electrolyte, Ni-P-SiC on cemented carbide is removed at the rate of 20μm/min or faster and the oxidative reaction stops by itself result from that cemented carbide forms passive state layer. Using these coating and stripping methods, resharpening process takes within only 5 minutes.

Conductometric determination of single pores in polyethylene terephthalate irradiated by heavy ions

Most of the previous works devoted to the problem of track formation processes did not pay enough attention to the direct measurement of appearance of every individual pore in an array of many pores induced by the irradiation of polymer films with ions. Such measurements are not easy to carry out due to the extremely high electric resistance at the moment of pore opening. In this work the analysis of films irradiated with low particle fluences up to 3.7×10 3 ions/ cm 2 will be described. As sample materials polyethylene terephthalate (PET) Hostaphan with a thickness of 20 μm were used. They were irradiated with Bi ions of 11.4 MeV/ amu energy. Using optimized etching conditions and computer-aided data evaluation, we obtained results which are in good agreement with theoretical predictions and model calculations. The measured increase in the conductivity beginning from the breakthrough of a single track up to the next pore opening in dependence with the etching time and the number of opened pores confirm the assumed model. Thus, the developed “track-by-track” method can be used effectively for description of the sequential appearance of individual pores in an electrolytic etching process.

Analysis of depth of the microporosity in a nickel-chromium system alloy - effects of electrolytic, chemical and sandblasting etching.

The present study was designed to analyse the average depth of the microporosity of a nickel-chromium (Ni-Cr) system alloy (Verabond II). The metal surface was subject to one of the following surface treatment: (i) Electrolytic etching in nitric acid 0.5 N at a current density of 250 mA cm(-2); (ii) chemical etching with CG-Etch etchant; and (iii) Sandblasting with alumina particles 50 microm. Half of the samples were polished before the surface treatments. The depth of porosity was measured through photomicrographs (500x) with a profilometer, and the data were statistically analysed using an analysis of variance (anova) followed by Tukey's test. The conclusions were (i) Differents surface treatment of the Ni-Cr system alloy lead to different depths of microporosity; (ii) The greatest depth of porosity was observed in non-polished alloy; (iii) The greatest and identical depth of microporosity was observed following electrolytic etching and chemical etching; (iv) The least and identical depth of microporosity was observed with chemical etching and sandblasting with alumina particles 50 microm, and (v) Chemical etching showed an intermediary depth.

A method to determine the opening process for pores of latent ion tracks in polymer using electrolytic etching

Up to now, most of studies have not considered direct measurements which would enable the detection of every pore separately while etching irradiated polymer films. It is not easy due to extremely high values of electric resistance in the moment of pore opening. In our studies presented here we used polyethylene terephthalate foils irradiated with swift heavy ions at low fluencies up to 3.7×10 3 ions/cm 2 (Bi ions, 11.4 MeV/nucleon, UNILAC, GSI Darmstadt). Using optimized etching conditions and computer program, we got interesting results. It was shown that the conductivity of the single tracks increases in time during etching, from the breakthrough up to the next pore opening. The “track-by-track” method therefore can be used for the conductometric and graphic description of subsequent pores’ appearance.

Characterizations and luminescence properties of annealed porous silicon films

Porous silicon (PS) samples were prepared by common electrochemical etching in HF-based electrolytes. Significantly increased current density (150 mA/cm 2) during anodization led to the accumulation of oxygen on the internal surface of the pores in the PS. Annealing of the samples was achieved in plasma of hydrogen for 15–30 min. During annealing at higher temperature (420–450°C) for 15 min or at lower temperature (250°C) for a longer time (30 min), the hydride coverage of the internal surface of the pores was replaced by a high-quality suboxide partially oxidized hydride layer or suboxide layer, as was shown by the evolution of infra-red absorption spectra due to annealing. Efficient violet and blue emissions were observed in these samples, which could be the result of the recombination of non-equilibrium carriers via an impurity center in the suboxide layer. In the sample that has a suboxide partially oxidized hydride layer, the luminescence mechanism needs a further investigation.

Enhanced Quantum Efficiency of Photocathode under High Electric Field

The dependence of quantum efficiency on a high electric field was investigated using a tungsten needle photocathode irradiated by a 3rd-harmonics Nd:YAG laser whose photon energies were lower than the work function of tungsten. The tungsten needles were fabricated by an electrolytic etching technique. The tip radii could be controlled between 0.1 and 1 µm by changing the etching conditions. The obtained quantum efficiency of the needle tip is found to be proportional to the >10th power of the electric over 500 MV/m, and it reached up to 3% at about 800 MV/m. This observed field-enhancement of quantum efficiency is qualitatively explained with a field-emission process including the Schottky effect and photo-excitation.

Deployment of fingertip forces in tactile exploration.

The purpose of this study was to examine how contact forces normal to the skin surface and shear forces tangential to the skin surface are deployed during tactile exploration of a smooth surface in search of a tactile target. Six naive subjects participated in two experiments. In the first experiment, the subjects were asked to explore a series of unseen smooth plastic surfaces by using the index finger to search for either a raised or recessed target. The raised targets were squares with a height of 280 micro m above the background surface and that varied in side lengths from 0.2 mm to 8.0 mm. A second series of smooth plastic surfaces consisted of small recessed squares (side lengths: 2.0, 3.0, 4.0 and 8.0 mm) that were etched to a depth of 620 micro m. Although made of an identical material, the plastic substrate had a lower coefficient of friction against the skin because only the recessed square had been subjected to the electrolytic etching process. The surfaces were mounted on a six-axes force and torque sensor connected to a laboratory computer. From the three axes of linear force, the computer was able to calculate the instantaneous position of the index finger and the instantaneous tangential force throughout the exploratory period. When exploring for the raised squares, the subjects maintained a relatively constant, average normal force of about 0.49 N with an average exploration speed of 8.6 cm/s. In contrast, all subjects used a significantly higher average normal force (0.64 N) and slightly slower mean exploration speed (7.67 cm/s) when searching for the small recessed squares. This appeared to be an attempt to maximize the amount of skin penetrating the recessed squares to improve the probability of target detection. In a second experiment, subjects were requested to search for an identical set of raised squares but with the fingertip having been coated with sucrose to impede the scanning movement by increasing the friction. Overall, the subjects maintained the same constant normal force that they used on the uncoated surface. However, they increased the tangential force significantly. The similarity of the search strategy employed by all subjects supports the hypothesis that shear forces on the skin provide a significant stimulus to mechanoreceptors in the skin during tactile exploration. Taken together, these data suggest that, in active tactile exploration with the fingertip, the tangential finger speed, the normal contact force, and the tangential shear force are adjusted optimally depending on the surface friction and whether the target is a raised asperity or a recessed indentation.

Dimensional Constraints on High Aspect Ratio Silicon Microstructures Fabricated by HF Photoelectrochemical Etching

The fabrication of macropores in crystalline silicon by photoelectrochemical etching in a hydrofluoric acid electrolyte is investigated. It is shown that the dimensional constraints on the pore diameters, which, in previous literature, are considered to depend on substrate doping, can be significantly relaxed. We show that it is possible to fabricate arrays of square section macropores with sides ranging from 2 to 15 μm using the same n-doped (2.4-4 Ω cm) silicon substrate. Moreover, we demonstrate that macropore arrays with pitch variation up to 100% (8 and 16 μm) can be simultaneously grown on the same silicon sample. The same process is used to fabricate arrays of silicon walls with different spacing and pitch as well. A simple model, based on the coalescence in a single pore of multiple stable pores, is proposed to explain the experimental data. © 2002 The Electrochemical Society. All rights reserved.

Hydroxyapatite deposition by electrophoresis on titanium sheets with different surface finishing.

Hydroxyapatite coatings are commonly applied to metallic biomedical implants to accelerate osseointegration. These coatings, usually produced by plasma spray techniques, can be obtained by alternative processes, like biomimetic process, electrolytic deposition, or electrophoretic process as well. Electrophoretic deposition of hydroxyapatite exhibits several advantages like simplicity and low cost. In this article, titanium sheets with three different surface finishing were coated with hydroxyapatite by using electrophoresis. Surface treatments include: (1) abrading with SiC paper; (2) abrading with SiC paper plus electrolytic etch with H3PO4 solution; and (3) blasting with alumina powder followed by etch with a solution containing H2O2 and HF. Stoichiometric hydroxyapatite was used to coat titanium sheets. Blasted samples were also coated using a calcium-deficient hydroxyapatite. SEM, XRD, and FTIR were employed to characterize titanium substrates and coatings produced. Results show that electrophoretic process can produce a uniform thin layer, satisfactorily adhered, of hydroxyapatite on treated titanium samples. Furthermore, sintering at 800 degrees C do not promote the decomposition of calcium-deficient hydroxyapatite.

Graining technology by electrolytic etching on the surface of aluminum alloys

The electrolytic etching solution of an aluminum alloy is comprised of the species forming a barrier layer on the surface of the aluminum alloy and the species etching the barrier layer. The experiments showed that in the sodium metaboricate—boric acid electrolysis system with sodium metaboricate as the main component, sodium carbonate as the etchant and sodium phosphate as the enhancing bond-agent—the electrolytically etched graining on the surface of the aluminum alloy are true to life, the depth of the mark is moderate. After the electrolytically etched graining is anodized and is then submitted to electrolytic coloring, the color comparison is obvious, and extremely similar to wood graining. The XRD diagrams show that the electrolytically etched surface of the aluminum alloy consists of aluminum and alumina, which mainly localized in the graining zone and exists in α-Al 2O 3 and γ-Al 2O 3. Having been anodized, SO 4 2− is introduced into the oxidized film; the pore density and the pore diameter of the multi-porous layer of the oxidized film in the graining zone are bigger than those in the grainless zone. Thus the inner depositing amounts in the micro-pores of the oxidized film in the graining zone are big, which would show dark color.

Selektive Phasenkontrastierung in ausgewählten Nickelbasis- Superlegierungen / Selective Phase Contrasting in Chosen Nickel Base Superalloys

The microstructural constituents found in the chosen Nickel base superalloys (Nimonic 80A -Bohler L306, Udimet 520 - Bohler L326, Inconel 718 - Bohler L334) can be identified with difficulty both in the Scanning Electron Microscope (SEM) and in the Transmission Electron Microscope (TEM). Different methods of etching were developed and tested to produce selective contrasting and therefore a clear differentiation between these constituents when viewed under the optical light microscope. Both classical chemical and electrolytic etching techniques were applied.

Observation of etch pits and defects in diamond single crystals prepared under high temperature–high pressure

As-grown diamond single crystals synthesized under high temperature–high pressure in the presence of FeNi catalyst were directly observed by scanning electron microscopy and transmission electron microscopy (TEM). Etch pits on the (1 1 1) surface of the diamond, which are generated by the screw dislocations meeting the diamond (1 1 1) surface at the points of emergence of dislocations, can be revealed by electrolytic etching and be used to study the motion of dislocations under the action of applied stress. Stacking-fault tetrahedral and stacking faults were investigated by moiré images. The stacking-fault tetrahedral and stacking faults may be derived from supersaturated vacancies generated during rapid cooling from high temperature to room temperature. Dislocation networks and an array of parallel dislocations were directly examined by TEM, which are related to the thermal stress caused by the inclusions in the diamond.

Preparation of AlN polycrystalline plate from aluminum plate

AlN was produced by nitriding electrolytically etched aluminum plate. It was found that the plate shape did not change. (100) Oriented aluminum plate (18×50×0.1 mm in size, 99.99% in purity) was suitable for the conservation of plate shape. Electrolytic etching and preheating at 600°C in N2 flow are essential for the complete nitriding. Although nitriding temperature (1100–1400°C) was much higher than the melting point of aluminum, the plate was completely nitrided without the destruction of shape. The surface film of aluminum oxide, which was formed by a trace amount of oxygen in N2 gas, conserved the plate shape during nitriding. The relative density of product was increased to 91% by sintering at 1800°C for 2 h.