Electrolytic Etching Technique Research Articles

Collaborative experiment of the work group “Sample Preparation” on the subject “Reduction of hazardous substances in metallographic etching using electrolytic etching techniques”

Abstract This article shows how conventional etching methods can be replaced by electrolytic processes, thereby reducing hazardous substances during etching. The joint experiment carried out on this topic by the “Sample Preparation” working group uses various materials to show how hazardous substances can be reduced, but also the existing limitations.

An Optimized Nontoxic Electrolytic Etching Procedure for Fine Art Printmaking

Abstract In their National Endowment for the Arts–funded project the authors sought to provide artists with an innovative method for creative expression using electrolytic etching techniques long used in the electronics and biotech industries. Using scientific methods, the electrolytic etching process was improved and then compared side by side with copper etched in ferric chloride after analysis with an AFM. The optimized electrolytic etching method proved to be superior to classical acid etching in intaglio printmaking.

Presentation and Verification of an Electrolytic Etching Technique for the Determination of prior Austenite Grain Boundaries in the Steel PH15-5

AbstractIn the field of hot working, modelling of austenite grain size makes a significant contribution to the prediction of future material properties. One of the difficulties when it comes to modelling is the detection of grain sizes at different recrystallization stages by means of etching methods. Especially with high-purity steels with a martensitic structure, imaging of prior austenite grain boundaries without simultaneous highlighting of lath martensite boundaries, is, in many cases, only possible to some extent when using etching technology. Due to small electrochemical potential differences, increased purity of the alloy causes a more uniform etching attack on grain and lath boundaries and thus leads to a poorer discrimination. An alternative technique for grain size determination is Electron Backscatter Diffraction (EBSD). However, this technique maps only a relatively small area of the sample and is also significantly more expensive than the combination of electrolytic etching and light microscopic analysis.Therefore, this work will present a novel electrolytic etching technique for light microscopic imaging of prior austenite grain boundaries in high-purity and corrosion-resistant grades of precipitation hardening steels. For this purpose, a series of tests was carried out on the alloy PH15-5 and the results were verified by correlative EBSD measurements.

Revealing the As-Cast and Homogenized Microstructures of Niobium-Bearing Nickel-Based Superalloy

The as-cast structure and its evolution during homogenization heat treatment for a typical nickel-based superalloy (Inconel 718) were studied based on different etching methods. Unambiguous revealing of the dendritic microstructure and the austenite/Laves eutectic constituent in the interdendritic areas was considered as the basis for the judgment for appropriateness of the etching techniques. Both chemical etching and electrolytic etching techniques were taken into account. The waterless Kalling’s reagent number 2 was found to be a suitable etchant for revealing the macrostructure of the alloy. It was also concluded that electroetching by a H2SO4 solution and by a solution containing HCl, HNO3 and glycerol are appropriate for studying the as-cast and homogenized microstructures based on optical microscopy and scanning electron microscopy (SEM), respectively. The dissolution of the Laves phase, the coarsening of the grains, and the development of annealing twins during exposure at elevated temperatures were also briefly discussed.

Investigating of the Field Emission Performance on Nano-Apex Carbon Fiber and Tungsten Tips

Field electron emission measurements have been performed on carbon-based and tungsten microemitters. Several samples of both types of emitters with different apex radii have been obtained employing electrolytic etching techniques using sodium hydroxide (NaOH) solution with different molarities depending on the material used. A suitable, home-built, field electron microscope (FEM) with 10 mm tip to screen separation distance was used to electrically characterize the electron emitters. Measurements were carried out under ultra high vacuum (UHV) conditions with base pressure of 10-9 mbar. The current-voltage characteristics (I-V) presented as Fowler-Nordheim (FN) type plots, and field electron emission images have been recorded. In this work, initial comparison of the field electron emission performance of these micro and nanoemitters has been carried out, with the aim of obtaining a reliable, stable and long life powerful electron source. We compare the apex radii measured from the micrographs obtained from the SEM images to those extracted from the FN-type _I-V_plots for carbon fibers and tungsten tips.

Effects of Hierarchical Micro/Nano-Textured Titanium Surface Features on Osteoblast-Specific Gene Expression

To investigate the influence of hierarchical hybrid micro/nano-textured titanium surface features on osteoblast differentiation. In this study, 3 different implant discs were produced: a hierarchical hybrid micro-/nanostructured titanium surface topography was modified using electrolytic etching (EE) technique, and a sandblasted, acid-etched (SLA) group and a machined (M) group were used as control groups. MG-63 cells were cultured on discs for 1 day to 7 days. The osteoblast response to the hierarchical hybrid micro-/nanostructured titanium surface was evaluated through the osteoblastic alkaline phosphatase (ALP) activity and gene (OCN, RUNX2, OPN, and Col-I) expression. On the first, third, fifth and seventh day, the ALP activity, OCN, RUNX2, OPN, and Col-I messenger RNA gene expression, levels of EE were higher in EE group than in M and SLA groups. Hierarchical hybrid micro-/nanostructured titanium surface has a favorable biocompatibility, which can promote osteoblast differentiation. It could possibly accelerate bone growth, promote bone formation at early stage, and guarantee the immediate loading and early stage loading in clinical practice.

SiC-C fiber electrode for biological sensing

Microelectrodes implanted in the brain can act as transducers for the neuronal impulses. In this work a composite fiber (SiC-C) electrode was studied for neuronal activity sensing and for biochemical detection of electroactive neurotransmitters. An electrolytic etching technique was also developed for fabricating electrode tips from SiC-C composite fiber. SEM was used to study different tip geometries and shapes. Cyclic voltammetry and electrochemical impedance spectroscopy were used for the electrochemical characterization and modeling. Almost square voltammograms showed that the current generated was due to the charging and discharging of the capacitive double layer without any significant redox reaction. The electrodes showed capacitive interaction with the surrounding electrolyte solution which is highly desirable for safe charge transfer. Biochemical sensing of neurotransmitters including dopamine hydrochloride and vitamin C was done with the SiC-C composite electrodes and oxidation currents were found to vary linearly with concentration. In vivo action potential recordings from anesthetized rat's brain with very high signal to noise ratio were obtained.

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.

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.

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.

A study of the magnetic structure of magnetic force microscope tips using transmission electron microscopy

Magnetic force microscopy (MFM) has become an important tool in the investigation of the micromagnetic structure of magnetic systems. The interaction of stray magnetic field from a sample with a sharp magnetic tip is measured as the tip is scanned across the surface of the sample. Characterisation of the tip-sample interaction is of paramount importance if the measured signal obtained by MFM is to be put on a quantitative basis. In this paper we describe the preliminary results obtained by studying MFM tips using the Lorentz techniques of transmission electron microscopy.The MFM tips were prepared from 25nm thick Ni wire by an electrolytic etching and polishing technique which produces tips with a sharp apex of radius <100nm. The nature of the tips meant that only the very end of the tips were thin enough to be observed using 200kV electrons in TEM.

Effectiveness of a method used in bonding resins to metal

Currently, several methods are available for bonding resin veneers to dental casting alloys. Recently a new system (Silicoater) has been developed that involves the chemical bonding of polymers to dental substrates. This study determined bond strengths of several proprietary composite resin luting agents to three different types of casting alloys. The results were compared with those obtained using electrolytic etching techniques. The pyrogenically silica-treated specimens generated the highest bond strengths.

Effect of cutting speed and tool rake angle on residual stress distribution in machining 2024-T351 aluminium alloy ? unlubricated conditions

The residual stress distribution in the machining of 2024-T351 aluminium alloy was measured using an electrolytic etching technique. Ring-shape specimens were machined under unlubricated orthogonal conditions with high-speed steel tools having rake angles of 10, 15, 20 and 25° at cutting speeds ranging between 0.5 and 1.25 m sec−1. The results of the investigation show that the residual stresses are compressive at the machined surface and decrease with depth beneath the machined surface. The maximum (near-surface) residual stress and the depth of the severely stressed region increase with an increase in the cutting speed. There seems to be little change in the residual stress distribution due to a change in the rake angle. The results are interpreted in terms of the variations in the amount of surface-region deformation produced by changes in cutting conditions.

A rapid method for production of sharp tips on preinsulated microwires

A rapid method is described which makes it possible to obtain sharp, pencil-like tips on factory-insulated tungsten wires. These features cannot be achieved on preinsulated wire using electrolytic etching techniques. In essence, the cut end of an insulated 25 μm wire is ground on a flat metal surface containing a thin layer of powdered diamond. When both the wire and the diamond-covered disc are rotated simultaneously, a sharp pointed tip is produced within 2–5 min with a smoothly tapering sleeve of insulation. The resulting tips yielded high-quality single-unit spike trains when tested in rat cochlear nucleus. This method lends itself well to those single unit or multineuronal studies requiring rapid, low-cost electrode production, and minimum tissue damage.

Residual Stress Distribution in Machining Annealed 18 Percent Nickel Maraging Steel

A novel electrolytic etching technique is used to determine the residual stress distribution in the machining of annealed 18 percent nickel maraging steel. Ring shaped specimens were machined under unlubricated orthogonal conditions with carbide cutting tools having wear lands of 0.125, 0.25, and 0.5 mm length at cutting speeds ranging between 0.05 and 1.60 ms−1. The results of the investigation show that the residual stresses are tensile at the machined surface and decrease with an increase in depth beneath the machined surface. The maximum (near surface) residual stress and depth of the severely stressed region increase with an increase in cutting speed and tool wear land length. The results are interpreted in terms of the variations in the amount of surface region deformation produced by changes in cutting conditions.

Etch Pit Pattern of GaAs Crystals Made by Light Irradiated Electrolytic Etching

A light-irradiated electrolytic etching technique was developed for GaAs crystals. This technique, which employs a chemical echant consisting of AgNO3, CrO3, HF and H2O, realize clear etch pit patterns in a thinly etched layer of GaAs. A square pattern and a triangular pattern appear on the {100} plane and {111} As plane, respectively. Etching depth is about one tenth that of traditional electrolytic etching without light. This makes application to accurate epitaxial layer evaluation possible. The patterns obtained by this method are shown to be dislocation pits by comparison with X-ray topography patterns. The clear patterns obtained can be made even when the etchant is at room temperature. The results open the way for practical evaluation of thin epitaxial layers.

Porosity in the base metal removable partial denture casting alloys relative to observable metallographic features

A series of tensile test pieces of the dimensions stated in the American Dental Association Specification No. 14 were produce using both nickel-base and cobalt-base removable partial denture casting alloys. Normal dental casting techniques were employed. Appropriate sections from each specimen were sectioned to half of their original thicknesses, embedded in heat-and pressure-cured conducting mounts, and polished for metallurgical examination. A double electrolytic etching technique was used, employing serially two solutions, in order to maximize the amount of metallographic detail visible. The method proved particularly valuable in the case of the nickel-base alloy as it indicated the presence of considerable interdendritic segregation. The incidence of porosity was evaluated throughout all sections of the specimens and, although found to be especially prevalent in those regions where gross shrinkage effects might be expected to occur, it was also shown to have a diffuse intergranular and interdendritic distribution.

Electrolytic etching and electron mobility of GaAs for FET's

An electrolytic etching technique for n-GaAs is presented. The procedure is applied to post-growth etching of FET wafers to achieve uniformly thin layers from excessively thick and nonuniform material. Measurements on a Hall sample, thinned by this technique, show mobilities in good agreement with theoretical bulk mobility calculations for films as thin as 2100 Å. From Hall measurements on layers covered by the anodic native oxide, it is determined that the oxide interface traps 3·9 × 10 11 electrons per cm 2 more charge than the as-grown surface.

An experimental investigation into the mechanics of deep semielliptical surface cracks in mode i loading

An experimental investigation was made of the surface deformation and extent of plastic yielding associated with relatively deep semielliptical surface cracks in plates subjected to tensile loading. Data were gathered from sheet Ti-6A1-4V and Fe-3Si, the latter material being employed to study, by the electrolytic etching technique, the plastic zones in various planes intersecting the crack. Available analytical models were applied to calculate the stress intensity factors, and the experimental data were used to examine various models for predicting plastic zone sizes.

Relation of GaAsP light emitter efficiency to zinc diffusion spike density

A new electrolytic etching technique has been utilized to remove the p-type zinc-diffused layer from GaAsP light emitting diodes. Actual device chips were examined before or after bonding to the header. The GaAsP material was grown from the vapor on (100) oriented GaAs substrates. Both isolated and multiple-associated spikes in the diffusion front are revealed on the (100) surface. Rapid etching of the p-type layer is carried out in a K3Fe(CN)6-KOH solution by placing an iron electrode against the diffused region. The etch rate slows drastically near the junction. Cross sections of the device chips, when cleaved and etched on (110) surfaces, show that the diffusion spikes are associated with dislocations originating at the interface with the GaAs substrates. In some material the diffusion spikes can be correlated with spots of en-hanced light emission, but in most rases little or no brightness varia-tion can be detected. A study of light emitter efficiency versus diffusion spike density shows that increased spike density in the range 3 x 105/cm2 to 3 x 107/cm2 decreases the efficiency at constant bias current.