Electrolytic Etching Research Articles

The Properties of Nanosized Silicon Prepared by Plasmochemical and Electrolytic (HCl : HF : C2H5OH ) Techniques

The structural and optical properties of nanostructured silicon obtained by plasmachemical and electrolytic techniques are presented. For electrolytic etching of silicon electrolyte the chlorine acid was added to standard HF:C2H5OH electrolyte. It was found that adding of HCl to the electrolyte slows the process of electrochemical etching thus creating conditions for efficient etching and formation of Si-O and Si-H bonds on the formed nanosilicon surface. In the present study the nanosilicon samples were obtained in ultra-high frequency plasmochemical system by means of recondensation of ultradispersed silicon powder in nitrogen flux heated to mean temperature of 3500 K. Morphology of films was found to consist of quantum nanowires of a mean diameter of 2 nm. Results indicating stability of nanosized silicon (NanoSi) under intense laser irradiation are presented. It is demonstrated that substantial increase of NanoSi photoluminescence signal can be attributed to their specific structure, as well as to the SiO2 thin film formed on the nanocrystalline surface.

Structure-Properties Relationship of TRIP-assisted Steels by Non-destructive Testing Method

This study was conducted on two TRIP-assisted steels (having low temperature (-40 0 C) high Charpy impact value) designated A (having no Cr and Cu content, VHN=169, UTS=542MPa) and B (having higher Ni, Cr and Cu content, VHN=217, UTS=657MPa).These steels were heattreated under different conditions to investigate correlation between heat treatment, microstructure and different properties. Micro-structural characterizations were carried out by optical microscope and scanning electron microscope after electrolytic etching. Non-destructive electro-chemical and ultrasonic testing on two TRIP-assisted steels were used to find out corrosion and mechanical properties of different alter microstructure phase's steels. Furthermore, micro-structural studies accompanied by the evaluation of mechanical properties revealed that steels having martensite phases with higher corrosive and hardness value were less sound velocity and also steel's microstructure having finer grains that was more grain boundary was less corrosion resistance. Steel containing more Cu, Ni and Cr was less corrosive compared to other steels having same processing or microstructure i.e. Rp (B) > Rp (A). The additions of alloying elements, such as Cu, Cr, Mo, Ni, etc. within the rust layer contribute to the improvement of electro-chemical characteristic of TRIP assisted steel. The corrosion current or icorr increases and corrosion resistance or Rp decreases with increasing Cl − ions

Electrochemical quartz crystal microbalance study of polyelectrolyte film growth under anodic conditions

Coating hard materials such as Pt with soft polymers like poly-l-lysine is a well-established technique for increasing electrode biocompatibility. We have combined quartz crystal microgravimetry with dissipation with electrochemistry (EQCM-D) to study the deposition of PLL onto Pt electrodes under anodic potentials. Our results confirm the change in film growth over time previously reported by others. However, the dissipation data suggest that, after the short initial phase of the process, the rigidity of the film increases with time, rather than decreasing, as previously proposed. In addition to these results, we discuss how gas evolution from water electrolysis and Pt etching in electrolytes containing Cl− affect EQCM-D measurements, how to recognize these effects, and how to reduce them. Despite the challenges of using Pt as an anode in this system, we demonstrate that the various electrochemical processes can be understood and that PLL coatings can be successfully electrodeposited.

Construction of micro–nano network structure on titanium surface for improving bioactivity

A novel hierarchical micro–nano structured titania layer was constructed on Ti surface to mimic the multi-level bone structure. The Ti substrate was subjected to a suitable acid etching and subsequent anodization in NaOH electrolyte to form a micro–nano porous titania layer. It was indicated that this microporous/nano-network (micro/nano-network) structured surface presented the enhanced wettability and superhydrophilic property. The polarization curve measurements showed that the as-prepared micro/nano-network structured TiO2 surface was of better corrosion resistance compared to the blank Ti surface, according to its corrosion current decreased, corrosion potential shifted positively and polarization resistance increased in Hank's solution. Meanwhile, the Mott–Schottky plots revealed that less oxygen vacancies existed in the micro/nano-network structured TiO2 film in contrast to the natural oxide film on blank Ti surface. Moreover, it was observed that the micro/nano-network structured surface was completely covered by a homogeneous apatite layer when immersed in simulated body fluid (SBF) for 14 days, exhibiting an excellent ability of biomineration. Furthermore, the superior cell adhesion and viability were discerned on such hierarchically structured surface, through a comparison of MG63 cell behaviors on blank Ti surface, nano-network structured surface and micro/nano-network structured surface. All results suggest our construction of micro–nano porous TiO2 surface is a promising strategy for improving the bioactivity of titanium implants.

Evaluation of Shear Bond Strength of Composite Resin Bonded to Alloy Treated With Sandblasting and Electrolytic Etching

Conservation of natural tooth structure precipitated the emergence of resin-retained fixed partial dentures. The weakest link in this modality is the bond between resin cement and alloy of the retainer. Various alloy surface treatment have been recommended to improve alloy-resin bond. This in vitro study was carried out to observe changes in the Nickel-Chromium alloy (Wiron 99, Bego) surface following sandblasting or electrolytic etching treatment by scanning electron microscope (SEM) and to evaluate the shear bond strength of a resin luting cement bonded to the surface treated alloy. 80 alloy blocks were cast and divided into four groups of 20 each. In groups-A & B, the test surfaces were treated by sandblasting with 50 and 250μm sized aluminium oxide particles respectively. In groups-C & D, the test surfaces were first treated by sandblasting with 50 and 250μm sized aluminium oxide particles respectively followed by electrolytic etching. Test surfaces were observed under SEM at 1,000× magnification. Two alloy blocks of each group were luted together by a resin luting cement (Rely X, 3M) and their shear bond strength was tested. The mean shear bond strength in MPa of groups-A to D were 6.44 (±0.74), 8.18 (±0.51), 14.45 (±0.59) and 17.43 (±1.20) respectively. Group-D showed bond strength that is more than clinically acceptable bond strength. It is recommended that before luting resin-retained fixed partial dentures, the fitting surface of the retainer should be electrolytically etched to achieve adequate micromechanical retention.

Micro-fabrication of air-bearing grooves onto inner surfaces of fine copper pipes

Applicability of laser-scan lithography onto inner surfaces of small-diameter pipes was investigated by fabricating fine air-bearing grooves. Herring bone patterns with a mean width of [email protected] were precisely formed on inner surfaces of copper pipes with an inner diameter of 2mm using laser direct writing lithography and sequent electrolytic etching. The pipe was cut and machined to a bearing bushing, and a rotor with the air-bearing bushing was fabricated. An aluminum hollow shaft was inserted in it, and the rotor was supported by the air bearing and magnetic thrust bearings placed at the both sides. As a result, the rotor was rotated very smoothly with a high-speed of more than 20,000rpm by blowing air to the rotor. Using conventional machining technology, it is difficult to form precise herring-bone shape grooves onto inner surfaces of such fine pipes. It was demonstrated that the combination of inside lithography and electrolytic etching was very useful for fabricating micro-mechanical components requiring precise patterning on their inside surfaces.

Hot Deformation and Dynamic Recrystallization of 17-4 PH Stainless Steel

)The hot deformation behavior of a 17-4 PH stainless steel was investigated by compression tests. Thetypical single-peak dynamic recrystalization (DRX) behavior and also a transition state between single andmultiple peak (cyclic) behaviors were seen in the resultant flow curves. The application of constitutiveequations for determination of hot working constants was critically discussed. As a result, the deformationactivation energy and the stress multiplier in the hyperbolic sine equation were determined as 337 kJ/moland 0.011, respectively. The Zener-Hollomon parameter (Z) exponents for peak stress and peak strainbased on the power relationships were determined as 0.18 and 0.11, respectively. The normalized criticalstress and strain for initiation of DRX were respectively found to be 0.89 and 0.47. The prior austenitegrain boundaries (PAGB) were revealed by electrolytic etching of the martensite in order to study themicrostructure of hot deformed samples. Significant grain refinement occurred as a result of necklaceDRX mechanism. The average dynamically recrystallized grain size was related to Z and peak stress bypower equations with exponents of –0.25 and –1.24, respectively. A DRX map was developed to show theeffect of deformation conditions on the occurrence of DRX and on the final grain size.KEY WORDS: hot deformation; dynamic recrystallization; grain refining; DRX map.

Microstructural Characterization of Carbides in a Cast High-Speed Steel Using Different Metallographic Techniques

Abstract High-speed steels are mostly manufactured by casting and they exhibit a characteristic dendritic microstructure with primary carbides. In this study, the morphology of carbides in a cast high-speed steel is investigated using light and scanning electron microscopes. The morphology and structure of the carbides were revealed by means of different metallographic techniques such as chemical and electrolytic etching and color metallography. The combination of these metallographic techniques gives different approaches to how different primary carbide morphologies can be observed in the martensitic structure. Besides, microanalysis was carried out to determine the chemical composition of primary carbides using SEM/EDX.

Influences of Grain Refining Conditions on Sensitization in 16 wt% Chromium Ferritic Stainless Steel Welds

The paper discusses sensitization characteristics in medium chromium Ferritic Stainless Steel (FSS) welds processed at two different grain refining conditions namely metal powder addition and cryogenic cooling. Tungsten Inert Gas (TIG) torch welded samples were exposed to 10% oxalic acid electrolytic etch for evaluation of sensitization. Empirical analysis indicated that, though both the grain refining conditions reduced the sensitization width relative to the conventional weld, the width was virtually nil with cryogenic cooling suggesting the elimination or reduction of sensitization. Similarly, the microstructure of cryogenically cooled welds showed no ditched grain boundary but aluminum powder treated welds revealed extensive ditching and none in titanium treated welds while knifeline attack was observed in welds treated with the mixture of aluminum and titanium powders.

Electrolytic Etching of Platinum-Aluminium Based Alloys

The microstructures of as-cast and annealed platinum alloys of different compositions were revealed after electrolytic etching in hydrochloric acid/sodium chloride solution using direct current. It was shown that the etching process enhances good microstructural images of platinum-aluminium based alloys.

Corrosion Behavior of Alloy 600 in Simulated Nuclear High Level Waste Medium

Nickel-based alloys are being considered as candidate materials for the storage of high level waste. In the present investigation, Alloy 600 was assessed by potentiodynamic anodic polarization technique for its corrosion behavior in the as-received, solution annealed, and sensitized condition in 3 M HNO3 and 3 M HNO3 containing simulated high level waste. From the results of the investigation, it was found that the solution annealed specimen possesses superior corrosion resistance compared to the as-received and sensitized specimen. Double loop electrochemical potentiokinetic reactivation test was carried out to study the degree of sensitization. The effect of different concentrations of chloride ions in 3 M HNO3 at 25 °C indicated tendency for pitting as the concentration of chloride ions was increased. Microstructural examination was carried out by optical microscope and scanning electron microscope after electrolytic etching. X-ray photoelectron spectroscopy study was carried out to investigate the passive film formed in 3 M HNO3 and 3 M HNO3 simulated high level waste.

Polymerized nanoporous titania surfaces: modification of cell adhesion by acrylic acid functionalization

Nanoporous titania (nPTI) has been prepared by electrochemical processes and functionalized by photochemical activation of condensed acrylic acid vapors (AcAc). The nPTI surfaces obtained after electrochemical etching in HF electrolytes at constant potential consisted of nanotube disordered arrays. Elastic recoil detection and Rutherford backscattering spectroscopy studies confirm the presence of an in-depth carbon based layer, previous to the AcAc polymerization. The subsequent AcAc functionalization affected only a few molecular monolayers since the process did not modify the nPTI structure observed by scanning electron microscopy. In fact, X-ray photoelectron spectroscopy confirms the presence of a carboxylic group contribution in the C 1s core-level spectrum only after AcAc polymerization of nPTI. Such results are of relevance for cellular attachment of human mesenchymal stem cells, whose adhesion onto nPTI is drastically enhanced after AcAc biofunctionalization.

Amorphous Al–Mn coating on NdFeB magnets: Electrodeposition from AlCl3–EMIC–MnCl2 ionic liquid and its corrosion behavior

Amorphous Al–Mn coating was electrodeposited on NdFeB magnets from AlCl3–EMIC–MnCl2 ionic liquid with the pretreatment of anodic electrolytic etching in AlCl3–EMIC ionic liquid at room temperature. The microstructure, composition and phase constituents of the coatings were investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The corrosion resistance of the coatings was tested by means of potentiodynamic polarization and immersion test in 3.5 wt. % NaCl solution. The results show that anodic electrolytic etching in AlCl3–EMIC ionic liquid is a satisfactory pretreatment to remove the surface oxide film and favor the adhesion of the Al–Mn alloy coating to the NdFeB substrate. The amorphous Al–Mn alloy coating provides sacrificial anodic protection for NdFeB. It exhibited good corrosion resistance and significantly reduced the corrosion current density of NdFeB by three orders of magnitude at potentiodynamic polarization.

Fabrication of precise copper micro-coils using electrolytic etching

Precise and homogeneous copper micro-coils were fabricated using electrolytic etching in aqueous solution of sodium chloride and ammonium chloride. It was clarified that the etching rate was hardly influenced by the resist pattern thickness and the etching voltage, but only depended on the helical space pattern width. Start and stop of the etching was exactly controlled by switching on and off the power supply circuit, and the etching was practiced under the room temperature without heating the specimens. The sidewall surfaces of the etched coils were very much smoother than those of the coils fabricated by the conventional chemical etching, and very favorable coil width homogeneity was obtained even for narrow space patterns with a width around [email protected]

Effect of Heat Treatment on Corrosion Behavior of Alloy 690 and Alloy 693 in Simulated Nuclear High-Level Waste Medium

Nickel-based alloys are being considered as candidate materials for the storage of high-level waste generated from the reprocessing of spent nuclear fuel. In the present investigation, Alloy 690 (UNS N06690) and Alloy 693 (UNS N06693) were assessed using the potentiodynamic anodic polarization technique for the corrosion behavior in the solution-annealed and sensitized conditions, in 3 M nitric acid (HNO3) and simulated high-level waste (HLW) at 25°C and 50°C. From the results of the investigation, it was found that the polarization curves for the solution-annealed specimens were characterized by a long passive range and low passivation current density, at 25°C. Increasing solution temperature to 50°C led to a corresponding increase in corrosion potential as well as passivation current density. The solution-annealed specimen showed improved corrosion resistance compared to the sensitized specimen in both media, for both alloys. Double-loop electrochemical potentiokinetic reactivation (DL-EPR) test was carried out for both solution-annealed and sensitized Alloy 690 and Alloy 693 in 0.5 M sulfuric acid (H2SO4) containing 0.0001 M potassium thiocyanate (KSCN), to measure the degree of sensitization (DOS). Microstructural examination was carried out by optical microscopy and scanning electron microscopy (SEM) after electrolytic etching. The results of the present investigation are discussed in the paper.

Macroporous Silicon Fabricated by HF Electrochemical Etching for Antireflective Application in Solar Cells

Macroporous silicon was fabricated by electrochemical etching in hydrogen fluoride (HF) electrolyte on P-type silicon wafers. By optimizing the etching condition, the obtained macroporous silicon presented pore diameter of about 2 μm and pore density of ~107/cm2. Such macroporous silicon gave out an excellent antireflective performance with the reflectance lower than 4% in a wide spectral range of 400-1000 nm. An a-Si:H/c-Si heterojunction solar cell was fabricated on such macroporous silicon to show its application potential.

Parametric Study of Carbide Precipitation in 16wt% Chromium Ferritic Stainless Steel (FSS) Welds

Other than grain coarsening, the loss of corrosion resistance in ferritic stainless steel (FSS) welds due to intergranular precipitation of chromium carbides restricts the use of the alloy for structural application. The use of cryogenic cooling offers dual opportunities for the control of weld geometry and grain structure in FSS. This results in improved mechanical properties but the effect on carbide precipitation was not investigated. In this paper, the effect of heat flux, welding speed and flow rate of cryogenic liquid on carbide precipitation in 16% chromium FSS welds are discussed. The use of cryogenic cooling reduces the size of the sensitized zone but this is not significantly affected by the flow rate of the cryogenic fluid. Compared to the conventional welding, the cryogenic cooling increases the cooling rate and reduces the martensite content in the high temperature heat affected zone (HTHAZ) by about 20%. This results in wider ditched-structure in welds made with flow rates lower than 0.052L/min. Cryogenic cooling produces more ditched weld microstructure revealed by electrolytic etching in oxalic acid; however, the structure is acceptable since no single grain boundary is completely surrounded by ditches.

The impact of melt flow on the grain orientation in solidifying metal alloys

Directional solidification experiments were performed in PbSn and AlSi alloys under the influence of a rotating magnetic field. The solidification process was started without forced melt convection before applying a sudden onset of the electromagnetic force. Just before and after the initiation of the magnetic field the grain structure was analysed. Electrolytic etching was used to identify grains having different orientations and related EBSD measurements provided quantitative values for the crystallographic orientation of the grains. Whereas a distinct asymmetric grain growth or a deflection of the columnar grains becomes obvious in case of forced melt flow, a perceivable modification of the crystal orientation cannot be detected.

Parametric Study of Carbide Precipitation in 16wt% Chromium Ferritic Stainless Steel (FSS) Welds

Other than grain coarsening, the loss of corrosion resistance in ferritic stainless steel (FSS) welds due to intergranular precipitation of chromium carbides restricts the use of the alloy for structural application. The use of cryogenic cooling offers dual opportunities for the control of weld geometry and grain structure in FSS. This results in improved mechanical properties but the effect on carbide precipitation was not investigated. In this paper, the effect of heat flux, welding speed and flow rate of cryogenic liquid on carbide precipitation in 16% chromium FSS welds are discussed. The use of cryogenic cooling reduces the size of the sensitized zone but this is not significantly affected by the flow rate of the cryogenic fluid. Compared to the conventional welding, the cryogenic cooling increases the cooling rate and reduces the martensite content in the high temperature heat affected zone (HTHAZ) by about 20%. This results in wider ditched-structure in welds made with flow rates lower than 0.052L/min. Cryogenic cooling produces more ditched weld microstructure revealed by electrolytic etching in oxalic acid; however, the structure is acceptable since no single grain boundary is completely surrounded by ditches.

Viscous Layer Formed in the Anodic Electrolytic Etching of Reactive Metals in Ionic Liquid

Viscous Layer Formed in the Anodic Electrolytic Etching of Reactive Metals in Ionic Liquid