Electrodeposited Ni/Al2O3 Composite Coating on NdFeB Permanent Magnets

2008 ◽  
Vol 373-374 ◽  
pp. 232-235 ◽  
Author(s):  
Hui Zhang ◽  
Yong Wei Song ◽  
Zhen Lun Song
Keyword(s):  
Electron Microscopy ◽  
Composite Coating ◽  
Permanent Magnets ◽  
Corrosion Potential ◽  
Electrochemical Impedance ◽  
Free Corrosion Potential ◽  
Al2o3 Composite ◽  
Nickel Electrolyte ◽  
Scanning Electron ◽  
Better Than

NdFeB permanent magnets are highly susceptible to corrosion in various environments. A new composite coating electrodeposited on NdFeB magnets was investigated in this paper. The Ni matrix film was firstly electrodeposited on NdFeB surface from watts nickel electrolyte, and then Ni/Al2O3 composite coating was successively electrodeposited on the Ni film. The microstructures of electrodeposited Ni coating and Ni/Al2O3 composite coating were observed by scanning electron microscopy (SEM). The corrosion behavior of Ni coating and Ni/Al2O3 composite coating in 3.5wt% NaC1 solution was studied by polarization curves and electrochemical impedance spectroscopy (EIS). The results showed that the Ni coating and Ni/Al2O3 composite coating could both provide adequate protection to NdFeB substrate. But the free corrosion potential of Ni/Al2O3 composite coating was more positive and the passivation region was more obvious when compared with Ni coating. Meantime, the capacitance loop diameter of Ni/Al2O3 composite coating was significantly larger than that of Ni coating ,which suggested that the anticorrosion resistance of Ni/Al2O3 composite coating was better than electroplated Ni coating.

scholarly journals Obtaining and Corrosion Performance of Composite Zinc Coatings with Incorporated Carbon Spheres

Coatings ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 665
Author(s):  
Nelly Boshkova ◽  
Kamelia Kamburova ◽  
Nikola Koprinarov ◽  
Mariana Konstantinova ◽  
Nikolai Boshkov ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Composite Coating ◽  
Electrochemical Impedance ◽  
Steel Substrate ◽  
Zinc Coating ◽  
Pluronic F127 ◽  
Carbon Sphere ◽  
Carbon Spheres ◽  
Scanning Electron

The present work describes one possible way to prepare a stable aqueous suspension of carbon sphere particles with a positive charge that is suitable for simultaneous electrodeposition with zinc on steel substrate. In order to stabilize the suspension against aggregation, tri-block amphiphilic copolymer Pluronic F127, which is commercially available, was adsorbed on the surface of carbon sphere particles. This polymer contained poly (ethylene oxide) blocks as hydrophilic segments and poly (propylene oxide) blocks as the hydrophobic part. Scanning electron microscopy and visual observations confirmed the stability of the obtained suspension. The carbon sphere particles were embedded into the zinc coating by the co-electrodeposition process. The surface morphology of the composite coating was investigated using scanning electron microscopy. The influence of the carbon spheres on the cathodic and anodic processes was evaluated with cyclic voltammetry studies. The electrochemical investigations were realized in a model corrosion medium (5% NaCl solution with pH 6.7) by application of selected methods such as polarization resistance, potentiodynamic polarization, and electrochemical impedance spectroscopy, which revealed higher protective ability of the composite coating against corrosion in an aggressive environment.

Assessment of the Corrosion Behavior of Nd-Fe-B Magnets Used in Dentistry

2008 ◽  
Vol 587-588 ◽  
pp. 57-61
Author(s):  
E.A. Martins ◽  
Isolda Costa ◽  
J.L. Rossi ◽  
Hercílio G. De Melo
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Corrosion Resistance ◽  
Corrosion Behavior ◽  
Permanent Magnets ◽  
Electrochemical Impedance ◽  
Test Solution ◽  
Potentiodynamic Polarization Curves ◽  
Diffusion Controlled ◽  
Scanning Electron

Permanent magnets based on intermetallic compounds are employed in dentistry to fix dental prosthesis. However, these materials are very sensitive to corrosion. In this study the corrosion behavior of a sintered commercial Nd-Fe-B magnet has been investigated at neutral pH in a phosphate buffered solution (PBS). With this aim demagnetized specimens were immersed in the test solution and their corrosion behavior were monitored at increasing test times by means of electrochemical impedance spectroscopy ( EIS ), potentiodynamic polarization curves and surface observation by scanning electron microscopy ( SEM ). Experimental results indicated that the corrosion resistance is seriously affected in this solution. Moreover, no decrease in the intensity of the corrosive attack was verified during test periods of up 4 hours. Impedance results have indicated the occurrence of diffusion controlled phenomenon, likely linked to the presence of pores in the magnet microstructure.

Electron Microscopic Observation of the Longitudinal Organization of Poly (p-Phenylene Terephthalamide) Fibers

1982 ◽  
Vol 40 ◽  
pp. 680-681
Author(s):  
Li Li-Sheng ◽  
L.F. Allard ◽  
W.C. Bigelow
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Scanning Electron Microscopy ◽  
Microscopic Observation ◽  
Electron Microscopic Observation ◽  
Electron Microscopic ◽  
Aromatic Polyamides ◽  
Radial Arrangement ◽  
Scanning Electron ◽  
Better Than

The aromatic polyamides form a class of fibers having mechanical properties which are much better than those of aliphatic polyamides. Currently, the accepted morphology of these fibers as proposed by M.G. Dobb, et al. is a radial arrangement of pleated sheets, with the plane of the pleats parallel to the axis of the fiber. We have recently obtained evidence which supports a different morphology of this type of fiber, using ultramicrotomy and ion-thinning techniques to prepare specimens for transmission and scanning electron microscopy.

Scanning Secondary Electron Microscopy of Myofibrils Using Transmission Techniques

1975 ◽  
Vol 33 ◽  
pp. 556-557
Author(s):  
M. K. Lamvik
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Carbon Films ◽  
Photographic Recording ◽  
Transmission Electron ◽  
Thin Carbon ◽  
The Common ◽  
Scanning Electron ◽  
Better Than ◽  
Cellular Organelles

When observing small objects such as cellular organelles by scanning electron microscopy, it is often valuable to use the techniques of transmission electron microscopy. The common practice of mounting and coating for SEM may not always be necessary. These possibilities are illustrated using vertebrate skeletal muscle myofibrils.Micrographs for this study were made using a Hitachi HFS-2 scanning electron microscope, with photographic recording usually done at 60 seconds per frame. The instrument was operated at 25 kV, with a specimen chamber vacuum usually better than 10-7 torr. Myofibrils were obtained from rabbit back muscle using the method of Zak et al. To show the component filaments of this contractile organelle, the myofibrils were partially disrupted by agitation in a relaxing medium. A brief centrifugation was done to clear the solution of most of the undisrupted myofibrils before a drop was placed on the grid. Standard 3 mm transmission electron microscope grids covered with thin carbon films were used in this study.

scholarly journals Waterborne Polyurea Coatings Filled with Sulfonated Graphene Improved Anti-Corrosion Performance

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 251
Author(s):  
Jijia Zhang ◽  
Jihu Wang ◽  
Shaoguo Wen ◽  
Siwei Li ◽  
Yabo Chen ◽  
...  
Keyword(s):  
Composite Coating ◽  
Water Resistance ◽  
Electrochemical Impedance ◽  
Water Immersion ◽  
Doping Content ◽  
Corrosion Performance ◽  
Water Contact ◽  
Sulfonated Graphene ◽  
Long Time ◽  
Scanning Electron

In this paper, an environmentally friendly waterborne polyurea (WPUA) emulsion and its corresponding coating were prepared, which was characterized by dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and scanning electron microscopy (SEM). To improve the performance of the coating, we doped sulfonated graphene (SG) into WPUA to prepare composite coating (SG/WPUA). SG can be uniformly dispersed in WPUA emulsion and is stable for a long time (28 days) without delamination. The water resistance of the composite coating with 0.3 wt.% SG nanofiller was improved; the water contact angle (WCA) result was SG/WPUA (89°) > WPUA (48.5°), and water absorption result was SG/WPUA (2.90%) < WPUA (9.98%). After water immersion treatment, SEM observation revealed that the SG/WPUA film only generated enlarged microcracks (100 nm) instead of holes (150–400 nm, WPUA film). Polarization curves and electrochemical impedance spectroscopy (EIS) tests show that SG nanosheets with low doping content (0.3 wt.%) are more conducive to the corrosion resistance of WPUA coatings, and the model was established to explain the mechanism.

ELECTROCHEMICAL INVESTIGATION OF 2-THIOHYDANTOIN DERIVATIVES AS CORROSION INHIBITORS FOR MILD STEEL IN ACIDIC MEDIUM

2021 ◽  
Author(s):  
Petar Stanić ◽  
◽  
Nataša Vukićević ◽  
Vesna Cvetković ◽  
Miroslav Pavlović ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mild Steel ◽  
Acidic Medium ◽  
Corrosion Inhibitors ◽  
Electrochemical Impedance ◽  
Electrochemical Investigation ◽  
Force Microscopy ◽  
Atomic Force ◽  
Hcl Solution ◽  
Scanning Electron

Four 2-thiohydantoin derivatives were synthesized and their corrosion inhibition properties on mild steel (MS) in 0.5M HCl solution was evaluated using usual gravimetric and electrochemical methods (weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS). Morphology of the metal surface was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The study has shown that these compounds provide good protection for mild steel against corrosion in the acidic medium.

scholarly journals Corrosion Inhibitive Action and Adsorption Behaviour of Justicia Secunda Leaves Extract as an Eco‐Friendly Inhibitor for Aluminium in Acidic Media

2021 ◽  
Vol 11 (5) ◽  
pp. 13019-13030
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Weight Loss ◽  
Electrochemical Impedance ◽  
Physical Adsorption ◽  
Charge Transfer Resistance ◽  
Aluminum Surface ◽  
Protective Film ◽  
Transfer Resistance ◽  
Scanning Electron

The extract of Justicia secunda (JS) leaves was investigated as an eco‐friendly corrosion inhibitor of aluminum in 0.5 M HCl using weight loss, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and scanning electron microscopy (SEM) techniques. The inhibitor concentrations used ranged from 50 to 250 ppm at 30, 40, and 50oC. Results show that Justicia secunda acts as a good inhibitor for aluminum. Its efficiency increased with increasing inhibitor concentration but decreased with increasing temperature. Maximum inhibition efficiency as high as 94.3% was found at 30°C for 250 ppm of the inhibitor with the weight loss technique. Tafel polarization results show that the extract acts as a mixed-type inhibitor. The Nyquist plots indicated decreasing double-layer capacitance and increasing charge transfer resistance on increasing JS concentration. The inhibition action occurred through the physical adsorption of the extract on the aluminum surface. The adsorption process was found to follow Langmuir adsorption isotherm. The formation of a protective film on the metal surface was confirmed by scanning electron microscopy.

Effect of the sample form on the corrosion behavior of steels for concrete in 3% NaCl medium

2021 ◽  
Vol 109 (2) ◽  
pp. 201
Author(s):  
Laidi Babouri ◽  
Cheikh Mokrani ◽  
Yassine El Mendili
Keyword(s):  
Electron Microscopy ◽  
Linear Polarization ◽  
Saline Solution ◽  
Electrochemical Impedance ◽  
Nacl Solution ◽  
Tafel Polarization ◽  
Eds Analysis ◽  
Corrosion Of Steel ◽  
Surface Morphologies ◽  
Scanning Electron

Corrosion of steel constitutes a major preoccupation in the field of civil engineering and the building sector. In this paper, we investigated the electrochemical behavior of two steel specimens with different forms (latched steel and smooth steel) in a 3 wt.% NaCl solution. For this purpose, we studied the steel samples by linear polarization, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The surface morphologies of the substrates were examined by scanning electron microscopy coupled with energy diffraction spectroscopy (SEM/EDS). Results of linear polarization, Tafel polarization curves and EIS show that latched steel (LS) is more susceptible to corrosion than smooth steel (SS) in saline solution. Gravimetric and SEM/EDS analysis after 10 days of immersion confirmed the results obtained by electrochemical methods. All of our results are in agreement and demonstrate that the sample form plays a key role in corrosion resistance.

Process Study on Prepared Al2O3-TiB2 Composite Coating by Reactive Spray

2012 ◽  
Vol 472-475 ◽  
pp. 309-312
Author(s):  
Xiao Ping Zhou ◽  
Ming Li ◽  
Xin Zhou
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Aluminum Alloy ◽  
Composite Coating ◽  
Milled Powder ◽  
X Ray ◽  
Phase Constituent ◽  
Process Study ◽  
High Microhardness ◽  
Scanning Electron

The microstructures and properties of Al2O3-TiB2 composite coating on the surface of the aluminum alloy by reactive spraying was studied. The influences of mechanical alloying and spraying temperature on the phase constituent and microstructure of the composite were analyzed by X-ray diffractometry(XRD) and scanning electron microscopy(SEM). The results indicate that Al2O3-TiB2 composite coating is obtained by plasma spraying using milled powder of Al，TiO2，B2O and B2O3. The coating possesses high microhardness of 1300 HV0.1.

scholarly journals Influence of Monomer Concentration on the Morphologies and Electrochemical Properties of PEDOT, PANI, and PPy Prepared from Aqueous Solution

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Shalini Kulandaivalu ◽  
Zulkarnain Zainal ◽  
Yusran Sulaiman
Keyword(s):  
Electron Microscopy ◽  
Electrochemical Properties ◽  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Electrochemical Impedance ◽  
Monomer Concentration ◽  
Lithium Perchlorate ◽  
Sem Images ◽  
Eis Measurements ◽  
Scanning Electron

Poly(3,4-ethylenedioxyhiophene) (PEDOT), polyaniline (PANI), and polypyrrole (PPy) were prepared on indium tin oxide (ITO) substrate via potentiostatic from aqueous solutions containing monomer and lithium perchlorate. The concentration of monomers was varied between 1 and 10 mM. The effects of monomer concentration on the polymers formation were investigated and compared by using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) measurements. FTIR and Raman spectra showed no changes in the peaks upon the increment of the concentration. Based on the SEM images, the increment in monomer concentration gives significant effect on morphologies and eventually affects the electrochemical properties. PEDOT electrodeposited from 10 mM solution showed excellent electrochemical properties with the highest specific capacitance value of 12.8 mF/cm2.

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