scholarly journals Structure and Corrosion Behavior of TiO2 Thin Films Deposited by ALD on a Biomedical Magnesium Alloy

Coatings ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 70
Author(s):  
Aneta Kania ◽  
Magdalena M. Szindler ◽  
Marek Szindler
Keyword(s):  
Thin Films ◽  
Corrosion Resistance ◽  
Corrosion Rate ◽  
Magnesium Alloys ◽  
Corrosion Behavior ◽  
Atomic Layer ◽  
Immersion Test ◽  
Mg Alloys ◽  
Tio2 Films ◽  
Tio2 Thin Films

Magnesium alloys have been investigated as temporary biomaterials for orthopedic applications. Despite their high osseointegration and mechanical (bone-like) properties, Mg alloys quickly degrade in simulated physiological media. Surface coatings can be deposited onto Mg alloys to slow the corrosion rate of these biomaterials in chloride-rich environments. TiO2 films show high potential for improving the corrosion resistance of magnesium alloys. This article presents the structural observations and corrosion behavior of TiO2 thin films deposited onto a MgCa2Zn1Gd3 alloy using atomic layer deposition (ALD). Surface morphologies were observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM), and Raman analysis of the deposited TiO2 films was also carried out. The corrosion behavior of the uncoated alloy and the alloy coated with TiO2 was measured in Ringer’s solution at 37 °C using electrochemical and immersion tests. The microscopic observations of the TiO2 thin films with a thickness of about 52.5 and 70 nm showed that the surface morphology was homogeneous without visible defects on the TiO2 surface. The electrochemical and immersion test results showed that the thin films decreased the corrosion rate of the studied Mg-based alloy, and the corrosion resistance was higher in the thicker TiO2 film.

The Corrosion Resistance of the Mg-Al-Ca-Sr Sand Casting Magnesium Alloys

2012 ◽  
Vol 326-328 ◽  
pp. 255-260 ◽  
Author(s):  
Andrzej Kiełbus ◽  
Tomasz Rzychoń ◽  
Joanna Michalska ◽  
Michal Stopyra
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Rate ◽  
Magnesium Alloys ◽  
Room Temperature ◽  
Immersion Test ◽  
Corrosion Layer ◽  
Sand Casting ◽  
Nacl Solution ◽  
Effective Barrier ◽  
Corrosion Rates

In this paper, the corrosion resistance of two sand-casting creep resistant magnesium alloys Mg-9Al-1.5Ca-0.3Sr and Mg-9Al-2.2Ca-0.8Sr in the salt environment has been investigated. Specimens of each alloy has been immersed in 3.5% NaCl solution at room temperature and successively taken out after 1, 2, 4, 5 and 9 days. After immersion test, the microstructure and the appearances of the corroded structure were examined. The corrosion rates of both investigated alloys increased lineally with increasing the exposure time in both solutions. Mg-9Al-1.5Ca-0.3Sr alloy exhibits the higher corrosion rate during the immersion test than Mg-9Al-2.2Ca-0.8Sr. The corrosion layer of both alloys consists of MgO, MgOH and phases containing Cl, Na, Al and Ca. The increase of Ca content in the Mg-9Al-2.2Ca-0.8Sr alloy improved the corrosion resistance due to the formation of the reticular (Mg,Al)2Ca phase, which acted as an effective barrier against corrosion.

scholarly journals CORROSION-BEHAVIOR ANALYSIS OF A Fe-Al LAYER IN SEAWATER CHARACTERIZED BY STATIC CHEMICAL ETCHING

2021 ◽  
Vol 55 (4) ◽  
Author(s):  
Ningning Li ◽  
Guang Chen ◽  
Guoyuan Sun ◽  
Xinhua Qi
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Rate ◽  
Behavior Analysis ◽  
Passive Film ◽  
Corrosion Behavior ◽  
Chemical Etching ◽  
Immersion Test ◽  
Layer Surface ◽  
Corrosion Pits ◽  
Static Corrosion

The static corrosion behavior of a Fe-Al layer was investigated with an immersion test in seawater, using XRD and SEM with EDS, testing the corrosion rate. The results showed that phases -Al2O3, Fe2O3 and MgO were the main corrosion products on the Fe-Al layer surface, while corrosion pits and holes were also observed. It was found that the Fe-Al layer fabricated at 750 °C exhibits a better corrosion resistance, having smaller corrosion pits and holes and also a low corrosion rate. This was related to a good formation ability of the alumina passive film.

Phosphate Conversion Coating on Diecast AZ91D and Its Corrosion Resistance

2005 ◽  
Vol 488-489 ◽  
pp. 819-822 ◽  
Author(s):  
Wan Qiu Zhou ◽  
Da Yong Shan ◽  
En Hou Han ◽  
Wei Ke
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Rate ◽  
Magnesium Alloys ◽  
Polarization Curve ◽  
Immersion Test ◽  
Amorphous Structure ◽  
Conversion Coating ◽  
Test Results ◽  
Complex Phosphate

A phosphate conversion coating was deposited on diecast AZ91D magnesium alloys, the film was a complex phosphate containing Mg and Al,which showed amorphous structure. Corrosion resistance of conversion coating in 3.5%NaCl was investigated by polarization curve. It was showed that the anodic branch of polarization curve for the phosphate conversion coating presented typical passivation characteristic. Immersion test results showed that the corrosion rate of phosphate conversion coating was less than that of chromate Dow7 film.

Retention of Surface Structure Causes Lower Density in Atomic Layer Deposition of Amorphous Titanium Oxide Thin Films

2021 ◽  
Author(s):  
Benjamin Rich ◽  
Yael Etinger-Geller ◽  
G. Ciatto ◽  
A Katsman ◽  
Boaz Pokroy
Keyword(s):  
Thin Films ◽  
Atomic Layer Deposition ◽  
Surface Structure ◽  
Titanium Oxide ◽  
Size Effects ◽  
Atomic Layer ◽  
Tio2 Films ◽  
Structural Modifications ◽  
Layer Deposition ◽  
Amorphous Tio2

Size effects and structural modifications in amorphous TiO2 films deposited by atomic layer deposition (ALD) were investigated. As with the previously investigated ALD-deposited Al2O3 system we found that the film’s...

Phase-gradient atomic layer deposition of TiO2 thin films by plasma-induced local crystallization

2021 ◽  
Author(s):  
Dohyun Go ◽  
Jaehyeong Lee ◽  
Jeong Woo Shin ◽  
Sungje Lee ◽  
Wangu Kang ◽  
...  
Keyword(s):  
Thin Films ◽  
Atomic Layer Deposition ◽  
Atomic Layer ◽  
Tio2 Thin Films ◽  
Phase Gradient ◽  
Layer Deposition

Epitaxy of Porous and Photocatalytically Active TiO2 Films at 50°C

2011 ◽  
Vol 64 (9) ◽  
pp. 1235 ◽  
Author(s):  
Gregory K. L. Goh ◽  
Kelvin Y. S. Chan ◽  
Gao S. Huang ◽  
Qui L. Tay
Keyword(s):  
Thin Films ◽  
Methylene Blue ◽  
Liquid Phase ◽  
Anatase Tio2 ◽  
Blue Dye ◽  
Tio2 Films ◽  
Methylene Blue Dye ◽  
Liquid Phase Deposition ◽  
Grown Film ◽  
Tio2 Thin Films

Epitaxial anatase TiO2 thin films were grown on (001) oriented SrTiO3 single crystal substrates by liquid phase deposition at 50°C. The film consisted of nanosized crystallites and exhibited a significant void fraction of 31 %. This contributed to the cracking of thicker films due to the generation of capillary stresses in the nanosized pores during drying. This porosity also comes in useful during the photodegradation of a methylene blue dye by an as-grown film.

scholarly journals Investigation of Corrosion Resistance Enhancement for Biodegradable Magnesium Alloy by Ball Burnishing Process

2020 ◽  
Vol 14 (2) ◽  
pp. 175-183 ◽  
Author(s):  
Chenyao Cao ◽  
Jiang Zhu ◽  
Tomohisa Tanaka ◽  
Dinh Ngoc Pham ◽  
◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Mass Loss ◽  
Immersion Test ◽  
Corrosion Products ◽  
Mg Alloys ◽  
Surface Finishing ◽  
Human Organism ◽  
Corrosion Mechanism ◽  
Ball Burnishing ◽  
Treated Sample

Magnesium and magnesium-based alloys are considered ideal materials for implants in orthopedic treatment because their stiffness is close to that of human bones, and they can be absorbed gradually in the human organism. However, a major issue in their actual application is that the corrosion speed of Mg alloys is very high in aggressive environments such as the human fluids. In previous studies, many approaches have been attempted to enhance the corrosion resistance of Mg alloys. In this research, ball burnishing, a mechanical surface finishing process, is applied to improve the corrosion resistance of Mg alloys by changing its surface properties. The influence of the burnishing parameters on the corrosion resistance is investigated, and the corrosion of a treated and non-treated sample are compared. The test material used is the AZ31 Mg alloy. Firstly, a comprehensive review of the effect of burnishing on the final microstructures is reported. The influence of burnishing on grain size, work-hardened layer thickness, crystal orientation, and residual stress of the sample is discussed. Secondly, by conducting an especially designed long-term immersion test, the mass loss and surface evolution of each sample are evaluated. The experimental results indicate that, under proper processing conditions, the mass loss of the treated sample (8.8 mg) can be reduced to 36% of the non-treated one (24.2 mg). To elucidate the mechanism behind corrosion resistance enhancement by burnishing, the samples treated with the optimal processing parameters found are immersed in an aggressive solution for 1, 3, 5, and 7 days. From the results of mass loss measurement and surface structure characterization, it was found that, among pitting, general, and intergranular corrosion, pitting corrosion is the dominant corrosion mechanism. The holes enlarge because pits combine together, representing the greatest portion of mass loss. The main mechanism enhancing corrosion resistance is the size reduction of the grains on the surface induced by ball burnishing, causing a denser distribution of corrosion products in the immersion test. These corrosion products protect the material underneath accelerated corrosion.

Corrosion Resistance of Mg Alloy with High Zn Concentration Including Impurity Cu

2021 ◽  
Vol 1016 ◽  
pp. 592-597
Author(s):  
Masato Ikoma ◽  
Taiki Morishige ◽  
Tetsuo Kikuchi ◽  
Ryuichi Yoshida ◽  
Toshihide Takenaka
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Rate ◽  
Mg Alloys ◽  
Mg Alloy ◽  
Second Phase ◽  
Transportation Industry ◽  
Primary Metal ◽  
Cu Content ◽  
Zn Concentration ◽  
Lower Corrosion Rate

Mg alloys are very attractive materials for transportation industry due to their toughness and lightness. Recycling Mg alloys is desired for energy saving that otherwise would be required to produce its primary metal. However, secondary produced Mg tends to contain a few impurity elements that deteriorate its corrosion resistance. For example, contamination of Mg alloy by Cu induces second phase of Mg2Cu and it works as strong cathode, resulting in the corrosion rate rapidly increasing. It was previously reported that the corrosion resistance of Mg with impurity Cu was remarkably improved by addition of alloying element Zn. Addition of Zn into Mg formed MgZn2 phase and incorporated Cu into MgZn2 phase instead of Mg2Cu formation. In this way, since Zn serves to improve the corrosion resistance of Mg, Mg alloy with high Zn concentration may form a lot of MgZn2 and may have better corrosion resistance even with high Cu concentration. In this work, the corrosion behavior of Mg-6mass%-1mass%Al (ZA61) with different Cu content up to 1mass% was investigated. As a result, ZA61-1.0Cu had much lower corrosion rate compared to Mg-0.2%Cu and the corrosion rate was almost the same as that of pure Mg.

scholarly journals Photocatalytic Degradation of Different VOCs in the Gas-Phase over TiO2 Thin Films Prepared by Ultrasonic Spray Pyrolysis

Catalysts ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 915 ◽  
Author(s):  
Ibrahim Dundar ◽  
Marina Krichevskaya ◽  
Atanas Katerski ◽  
Malle Krunks ◽  
Ilona Oja Acik
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Photocatalytic Degradation ◽  
Spray Pyrolysis ◽  
Tio2 Thin Film ◽  
Ultrasonic Spray Pyrolysis ◽  
Airflow Rate ◽  
Tio2 Films ◽  
Tio2 Thin Films ◽  
Ultrasonic Spray

In this study, we deposited TiO2 thin films onto borosilicate glass by ultrasonic spray pyrolysis at 350 and 450 °C. The aim of study is to determine the effect of deposition temperature on photocatalytic activity of TiO2 thin films and to investigate the performance of TiO2 thin films on photocatalytic degradation of methyl tert-butyl ether (MTBE), acetone, acetaldehyde, and heptane as functions of different operating parameters. TiO2 thin films deposited at 350 and 450 °C have a thickness value of 190 and 330 nm, respectively. All as-prepared TiO2 films possess an anatase crystalline structure. According to the X-ray photon spectroscopy (XPS) study, the TiO2 thin film deposited at 350 °C showed a higher amount of oxygen vacancies and hydroxyl groups on the film surface after UV treatment. The aged-TiO2 thin film deposited at 350 °C showed a water contact angle (WCA) value of 0° after 10 min UV irradiation, showing superhydrophilic surface behavior. The TiO2 film deposited at 350 °C exhibited the highest amount of conversion of MTBE (100%). The results also showed that TiO2 films are capable of photocatalytic degradation of MTBE (100%) and acetaldehyde (approx. 80%) in humid air conditions and high airflow rate. The visible-light-activity of TiO2 thin films was tested with 5 ppm MTBE and acetone. TiO2 thin films deposited at 350 °C with a surface area of 600 cm2 showed 60% of MTBE and 33% of acetone degradation under VIS light.

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