Effects of RPM, Bath Temperature and Anodizing Time in Anodizing for Mg-Al Alloy under Constant Current

2007 ◽  
Vol 544-545 ◽  
pp. 291-294
Author(s):  
Seong Jong Kim ◽  
Jeong Il Kim
Keyword(s):  
Anodic Oxide ◽  
Bath Temperature ◽  
Constant Current ◽  
Al Alloy ◽  
Optimum Conditions ◽  
Constant Current Density ◽  
Active Dissolution ◽  
Dissolution Reaction ◽  
Naoh Solution ◽  
Time Required

We studied the effects of solution RPM, bath temperature, and time in anodizing AZ91 under a constant current density of 750 mA/cm2 in a 1 M NaOH solution. In general, increasing the anodizing time, RPM, and temperature of the bath improved the corrosion resistance. The thickness of the anodic oxide film likely grew by increasing the time required to generate the active dissolution reaction. When anodizing at 750 mA/cm2, we evaluated a 300–3600-s range in anodizing time, 0–1500 RPM, and 296–373 K bath temperatures, and determined that 3600 s, 1500 RPM, and 373 K comprised the optimum conditions.

Effects of Anodizing Time on Anodizing of Mg-Al Alloy in Alkaline Solution

2006 ◽  
Vol 510-511 ◽  
pp. 686-689
Author(s):  
Seong Jong Kim ◽  
Jeong Il Kim
Keyword(s):  
Oxide Film ◽  
Film Thickness ◽  
Alkaline Solution ◽  
Anodic Oxide ◽  
Anodic Oxide Film ◽  
Al Alloy ◽  
Active Dissolution ◽  
Dissolution Reaction ◽  
Edx Analyses ◽  
Time Required

This paper investigated the effects of anodizing time on the formation of anodic oxide films on a Mg-Al alloy in alkaline solution. The thickness of the anodic oxide film was increased by increasing the time required to generate the active dissolution reaction. When anodizing at various anodizing time, the potential after passivity increased with time, which implies growth in film thickness. When the anodizing time was varied, the quantity of oxygen increased with time in the white areas (the film), i.e., more film was observed in the SEM and EDX analyses.

Effects of the Duration of Potentiostatic Anodizing on the Corrosion Resistance and Surface Morphology of Films Formed on Mg-Al Alloys

2005 ◽  
Vol 486-487 ◽  
pp. 125-128 ◽  
Author(s):  
Seong Jong Kim ◽  
Seok Ki Jang ◽  
Jeong Il Kim
Keyword(s):  
Corrosion Resistance ◽  
Surface Morphology ◽  
Anodic Oxide ◽  
Al Alloys ◽  
Anodic Film ◽  
Al Alloy ◽  
Active Dissolution ◽  
Dissolution Reaction ◽  
Alloy Az91 ◽  
Morphology Of Films

The effects of the duration of potentiostatic anodizing on the corrosion resistance and surface morphology of anodic oxide films formed on Mg-Al alloy (AZ91) in 1 M NaOH were investigated. With the formation of an anodic film, the current density decreased gradually, started to stabilize at 300 s, and was relatively constant at 600 s. These results may be related to the increased time for catalysis of the active dissolution reaction, which not only enlarges the area covered by the anodic film, but also produces a more coherent, thicker film. The reference corrosion potentials of the anodic oxide film for AZ91 shifted in the noble direction with time. In general, the corrosion resistance characteristics were improved with anodizing time.

PHOTOLUMINESCENCE OF NON-CRYSTALLINE ALUMINA NANOWIRES SYNTHESIZED BY DIRECT ANODIZATION OF ALUMINUM

2009 ◽  
Vol 23 (14) ◽  
pp. 1819-1825
Author(s):  
JAYA SARKAR ◽  
GOBINDA GOPAL KHAN ◽  
A. BASUMALLICK
Keyword(s):  
Light Emission ◽  
Pure Aluminum ◽  
Bath Temperature ◽  
Constant Current ◽  
X Ray Diffraction ◽  
Constant Current Density ◽  
X Ray ◽  
Anodization Process ◽  
Potential Applications ◽  
Crystalline Alumina

Alumina nanowires have been synthesized by a simple electrochemical route, by tailoring the anodization process of aluminum. Two-stage anodization of pure aluminum foils were carried out in 0.3 M oxalic acid electrolyte by maintaining a constant current density of 250 A/m2 and suitably controlling the other anodization parameters: anodization voltage, bath temperature and anodization time. The fabricated alumina nanowires were investigated by field-emission scanning electron microscope (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Moreover, the X-ray diffraction (XRD) study on the prepared nanowires shows that they are non-crystalline in nature. The photoluminescence (PL) spectra of alumina nanowires exhibit two stable emission bands at 438 and 581 nm. The blue luminescence behavior of the alumina nanowires are attributed to the oxygen-deficient defect centers. PL study of alumina nanowires shows that they have potential applications in light emission devices.

Effects of Current Density on the Formation of Anodic Oxide Films on AZ91

2006 ◽  
Vol 510-511 ◽  
pp. 166-169
Author(s):  
Seong Jong Kim ◽  
Jeong Il Kim
Keyword(s):  
Corrosion Resistance ◽  
Current Density ◽  
Anodic Polarization ◽  
Oxide Films ◽  
Anodic Oxide ◽  
Anodic Polarization Curve ◽  
Al Alloy ◽  
Anodic Oxide Films ◽  
Active Metal ◽  
Naoh Solution

Magnesium must be surface treated to prevent corrosion, since it is a very active metal electrochemically. On anodizing, a compact film several tens of micrometers thick forms on magnesium, which imparts good corrosion resistance. The Mg-Al alloy (AZ91) was anodized in 1 M NaOH solution. The surface morphology of the anodized films was observed using scanning electron microscopy (SEM), energy-dispersive x-ray (EDX), and electrochemical methods. The effects of current density on the formation of anodic oxide films for a Mg-Al alloy in 1 M NaOH were investigated. In the anodic polarization curve, the reference corrosion potentials were far greater at 4-9 mA/cm2 than at 1 mA/cm2. The film that formed at 1 mA/cm2 was thin, suggesting that parts of the film had been dissolved or destroyed during the anodic polarization test. Corrosion resistance differed owing to concentric differences in current flow. Thick anodic oxide films were formed at higher applied currents.

scholarly journals A Research on Niw Alloy Coatings on Mild Steel through Electrodeposition Method

2019 ◽  
Vol 8 (9S2) ◽  
pp. 442-445
Keyword(s):  
Mechanical Properties ◽  
Mild Steel ◽  
Deposition Time ◽  
Wear Behavior ◽  
Hardness Test ◽  
Bath Temperature ◽  
Constant Current ◽  
X Ray Diffraction ◽  
Constant Current Density ◽  
Pin On Disc

In order to enhance the structural and mechanical properties of mild steel, NiW nanocrystalline thin layer has been coated on the surface of mild steel through electroplating technique at bath temperature of 40 C over the deposition time of 45 minutes. The nanocrystalline NiW alloy coatings were deposited on mild steel at constant current density of 1 A/dm2 . The structural and chemical characterizations of the NiW alloy coated mild steel were performed by scanning electron microscopy (SEM) and X-ray diffraction pattern (XRD). The micro hardness value of the coated mild steel was determined by using Vickers Hardness test. The effect of NiW on wear behavior of mild steel was analyzed using Pin-on-disc apparatus. The mechanical properties of mild steel such as hardness, roughness and wear resistance have been enhanced in an appreciable manner. This is primarily due to the NiW alloy coatings on mild steel. The variations in structural and mechanical properties of NiW coated mild steel were also studied

The morphology and mechanism of formation of porous anodic films on aluminium

1970 ◽  
Vol 317 (1531) ◽  
pp. 511-543 ◽  
Keyword(s):  
Steady State ◽  
Layer Thickness ◽  
Current Density ◽  
Barrier Layer ◽  
Anodic Oxide ◽  
Constant Current ◽  
Cell Diameter ◽  
Anodic Films ◽  
Constant Current Density ◽  
Barrier Layer Thickness

The morphology of porous anodic oxide films formed on aluminium in phosphoric acid electrolytes at constant current density or voltage, and under changing electrical or electrolytic conditions, has been studied quantitatively by electron microscopy. Replicas from film sections and from both film interfaces have been prepared, as well as transmission micrographs of thin films, produced under accurately defined conditions. During formation at constant current density, pore initiation occurs by the merging of locally thickening oxide regions, which seem related to the substructure of the substrate, and the consequent concentration of current into the residual thin areas. The pores grow in diameter and change in number until the steady-state morphology is established. The film barrier layer thickness has been measured directly for the first time. The steady-state barrier-layer thickness, cell diameter and pore diameter are all observed to be directly proportional to the formation voltage. It becomes evident that the barrier-layer thickness, decided largely by an equilibrium established between oxide formation in the barrier-layer and field-assisted dissolution (probably thermally enhanced) at the pore bases, determines the cell and pore sizes by a simple geometrical mechanism. Anion incorporation into the film and its hydrogen-bonded structure play secondary roles to these factors in determining the actual film morphology, although not its subsequent properties. A consequence of the mechanism is that, at constant current density, relatively non-aggressive electrolytes give thicker barrier layers, larger cells and larger pores next to the barrier layer than aggressive media, although subsequent pore widening at the outer surface of the film by simple chemical dissolution is more severe in aggressive electrolytes.

Reducing the Ecotoxicity of Pesticide Polluted Waters by Electrochemical Methods

2019 ◽  
Vol 70 (5) ◽  
pp. 1574-1578
Author(s):  
Cristian Neamtu ◽  
Bogdan Tutunaru ◽  
Adriana Samide ◽  
Alexandru Popescu
Keyword(s):  
Nitrogen Atmosphere ◽  
Constant Current ◽  
Polluted Water ◽  
Gaseous Nitrogen ◽  
Constant Current Density ◽  
Electrochemical Approach ◽  
Saline Waters ◽  
Thermal Combustion ◽  
Polluted Waters ◽  
Thermal Stability Of

Electrochlorination constitutes an electrochemical approach for the treatment of pesticide-containing wastewaters. This study evaluated the electrochemical and thermal stability of four pesticides and the efficiency of electrochlorination to remove and detoxify the simulated polluted water with: Acetamiprid, Emamectin, Imidacloprid and Propineb. This study reports the experimental results obtained by cyclic voltammetry and electrolysis at constant current density in association with UV-Vis spectrophotometry. In saline waters this pesticides are electrochemical active and anodic peaks are registered in the corresponding voltammograms. After thermal combustion, in a gaseous nitrogen atmosphere, a residue ranging from 15 to 45 % is observed at 500 �C.

60 GHz-Band Low-Noise Amplifier

2017 ◽  
Vol 26 (05) ◽  
pp. 1750075 ◽  
Author(s):  
Najam Muhammad Amin ◽  
Lianfeng Shen ◽  
Zhi-Gong Wang ◽  
Muhammad Ovais Akhter ◽  
Muhammad Tariq Afridi
Keyword(s):  
Transmission Line ◽  
Quality Factor ◽  
Noise Figure ◽  
Cmos Technology ◽  
Low Noise ◽  
Constant Current ◽  
60 Ghz ◽  
Frequency Range ◽  
Constant Current Density ◽  
Chip Area

This paper presents the design of a 60[Formula: see text]GHz-band LNA intended for the 63.72–65.88[Formula: see text]GHz frequency range (channel-4 of the 60[Formula: see text]GHz band). The LNA is designed in a 65-nm CMOS technology and the design methodology is based on a constant-current-density biasing scheme. Prior to designing the LNA, a detailed investigation into the transistor and passives performances at millimeter-wave (MMW) frequencies is carried out. It is shown that biasing the transistors for an optimum noise figure performance does not degrade their power gain significantly. Furthermore, three potential inductive transmission line candidates, based on coplanar waveguide (CPW) and microstrip line (MSL) structures, have been considered to realize the MMW interconnects. Electromagnetic (EM) simulations have been performed to design and compare the performances of these inductive lines. It is shown that the inductive quality factor of a CPW-based inductive transmission line ([Formula: see text] is more than 3.4 times higher than its MSL counterpart @ 65[Formula: see text]GHz. A CPW structure, with an optimized ground-equalizing metal strip density to achieve the highest inductive quality factor, is therefore a preferred choice for the design of MMW interconnects, compared to an MSL. The LNA achieves a measured forward gain of [Formula: see text][Formula: see text]dB with good input and output impedance matching of better than [Formula: see text][Formula: see text]dB in the desired frequency range. Covering a chip area of 1256[Formula: see text][Formula: see text]m[Formula: see text]m including the pads, the LNA dissipates a power of only 16.2[Formula: see text]mW.

Study on Special Morphology Hydroxyapatite Bioactive Coating by Electrochemical Deposition

2013 ◽  
Vol 537 ◽  
pp. 256-260
Author(s):  
Cai Ge Gu ◽  
Qian Gang Fu ◽  
He Jun Li ◽  
Jin Hua Lu ◽  
Lei Lei Zhang
Keyword(s):  
Electrochemical Deposition ◽  
Current Density ◽  
Electrolyte Concentration ◽  
Spherical Particles ◽  
Constant Current ◽  
Constant Current Density ◽  
Depth Direction ◽  
Special Morphology ◽  
Calcium Phosphate Coatings ◽  
Coating Weight

Bioactive calcium phosphate coatings were deposited on carbon/carbon（C/C） composites using electrochemical deposition technique. The effects of electrolyte concentration and constant current density on morphology, structure and composition of the coating were systematically investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy. The results show that, the coating weight elevated gradually with the increase of electrolyte concentration, and the morphology of coatings changed from spherical particles to nanolamellar crystals with interlocking structure initially. Then the coating transformed into seaweed-like and nano/micro-sized crystals along the depth direction of the coating. The coatings showed seaweed-like morphology as the deposition current density was less than 20mA. With the less current density, the coating became more homogenous. However, the coating was fiakiness crysal, with needlike crystal stacked upside as the current density reached to 20mA/cm2. The coating weight was improved gradually when the current density increased from 2.5mA/cm2 to 10mA/cm2, then reduced with the increasing current density in the range of 10 to 20mA/cm2.

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