scholarly journals A comprehensive study on the microstructure evolution and oxidation resistance of conventional and nanocrystalline MCrAlY coatings

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Farzin Ghadami ◽  
Alireza Sabour Rouh Aghdam ◽  
Soheil Ghadami
Keyword(s):  
Electron Microscope ◽  
Oxidation Resistance ◽  
Photoelectron Spectroscopy ◽  
Oxidation Behavior ◽  
Early Stage ◽  
Deposition Process ◽  
Nanocrystalline Powders ◽  
X Ray ◽  
Mcraly Coating ◽  
Mcraly Coatings

AbstractConventional and nanocrystalline MCrAlY coatings were applied by the high-velocity oxy-fuel (HVOF) deposition process. The ball-milling method was used to prepare the nanocrystalline MCrAlY powder feedstock. The microstructure examinations of the conventional and nanocrystalline powders and coatings were performed using X-ray diffraction (XRD), high-resolution field emission scanning electron microscope (FESEM) equipped with energy-dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS). Williamson–Hall analyzing method was also used for estimation of the crystalline size and lattice strain of the as-milled powders and sprayed coatings. Owing to the investigation of the oxidation behavior, the freestanding coatings were subjected to isothermal and cyclic oxidation testing at 1000 and 1100 °C under static air. The results showed that the conventional as-sprayed MCrAlY coating had a parabolic behavior in the early stage and prolonged oxidation process. On the contrary, in the case of the nanocrystalline MCrAlY coating, the long-term oxidation behavior has deviated from parabolic to sub-parabolic rate law. Moreover, the results also exemplified that the nanocrystalline MCrAlY coating had a greater oxidation resistance following the creation of a continuous and slow-growing Al2O3 scale with a fine-grained structure. The nucleation and growth mechanisms of the oxides formed on the nanocrystalline coating have also been discussed in detail.

X-ray photoelectron spectroscopy studies of the early-stage oxidation behavior of (Pt, Ni)3Al(111) surfaces in air

2008 ◽  
Vol 602 (1) ◽  
pp. 205-215 ◽  
Author(s):  
F. Qin ◽  
J.W. Anderegg ◽  
C.J. Jenks ◽  
B. Gleeson ◽  
D.J. Sordelet ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Oxidation Behavior ◽  
Early Stage ◽  
X Ray ◽  
Spectroscopy Studies

scholarly journals Preparation and Characterization of Visible-Light-Activated Fe-N Co-Doped TiO2and Its Photocatalytic Inactivation Effect on Leukemia Tumors

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Kangqiang Huang ◽  
Li Chen ◽  
Jianwen Xiong ◽  
Meixiang Liao
Keyword(s):  
Electron Microscope ◽  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
Light Therapy ◽  
Cell Counting ◽  
Visible Absorption ◽  
X Ray ◽  
Photocatalytic Inactivation ◽  
Inactivation Efficiency ◽  
Co Doped

The Fe-N co-doped TiO2nanocomposites were synthesized by a sol-gel method and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), ultraviolet-visible absorption spectroscopy (UV-vis) and X-ray photoelectron spectroscopy (XPS). Then the photocatalytic inactivation of Fe-N-doped TiO2on leukemia tumors was investigated by using Cell Counting Kit-8 (CCK-8) assay. Additionally, the ultrastructural morphology and apoptotic percentage of treated cells were also studied. The experimental results showed that the growth of leukemic HL60 cells was significantly inhibited in groups treated with TiO2nanoparticles and the photocatalytic activity of Fe-N-TiO2was significantly higher than that of Fe-TiO2and N-TiO2, indicating that the photocatalytic efficiency could be effectively enhanced by the modification of Fe-N. Furthermore, when 2 wt% Fe-N-TiO2nanocomposites at a final concentration of 200 μg/mL were used, the inactivation efficiency of 78.5% was achieved after 30-minute light therapy.

Preparation of Carbon Nanofibers from Polyacrylonitrile Nanofibers by Electrospinning

2011 ◽  
Vol 415-417 ◽  
pp. 642-647
Author(s):  
En Zhong Li ◽  
Da Xiang Yang ◽  
Wei Ling Guo ◽  
Hai Dou Wang ◽  
Bin Shi Xu
Keyword(s):  
Electron Microscope ◽  
Carbon Nanofibers ◽  
Photoelectron Spectroscopy ◽  
Solution Concentration ◽  
Dimethyl Formamide ◽  
Ultrafine Fibers ◽  
X Ray ◽  
Scanning Electron ◽  
Pan Fibers

Ultrafine fibers were electrospun from polyacrylonitrile (PAN)/N,N-dimethyl formamide (DMF) solution as a precursor of carbon nanofibers. The effects of solution concentration, applied voltage and flow rate on preparation and morphologies of electrospun PAN fibers were investigated. Morphologies of the green fibers, stabilized fibers and carbonized fibers were compared by scanning electron microscope (SEM). The diameter of PAN nanofibers is about 450nm and the distribution of diameter is well-proportioned. Characterization of the elements changes of fibers were performed by X-ray photoelectron spectroscopy (XPS).

High Temperature Oxidation Behavior of SUS310S Austenitic Stainless Steel

2014 ◽  
Vol 941-944 ◽  
pp. 212-215
Author(s):  
Tao Zheng ◽  
Jing Tao Han
Keyword(s):  
Photoelectron Spectroscopy ◽  
Oxidation Behavior ◽  
Layer Structure ◽  
Energy Dispersive Spectrometer ◽  
Austenitic Stainless Steels ◽  
Temperature Oxidation ◽  
X Ray ◽  
High Temperature Oxidation Behavior ◽  
High Oxidation Resistance ◽  
Ray Diffusion

The oxidation behavior of SUS310S austenitic stainless steels was studied in isothermal conditions at different temperatures between 800oC and 1100oC for 96h in air. The oxidation kinetics was analyzed, the surface and cross-section of the oxide scale grown by oxidation were characterized by using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffusion (XRD) and X-ray photoelectron spectroscopy (XPS). The SUS310S steel has high oxidation resistance at 800oC and with the increase of the temperature, the parabolic rate constants is constantly increasing. Examination of the morphology and composition of oxide layers reveals a double-layer structure, The inner layer is mainly chromium oxide (Cr2O3) and is covered by an uneven thinness outer layer of manganese-chromium or iron-chromium spinel oxide.

GROWTH OF OXIDE LAYER ON GERMANIUM (011) SUBSTRATE UNDER DRY AND WET ATMOSPHERES

1999 ◽  
Vol 06 (06) ◽  
pp. 1053-1060 ◽  
Author(s):  
N. TABET ◽  
J. AL-SADAH ◽  
M. SALIM
Keyword(s):  
Simple Model ◽  
Oxide Film ◽  
Growth Kinetics ◽  
Photoelectron Spectroscopy ◽  
Early Stage ◽  
X Ray ◽  
Apparent Thickness ◽  
Different Temperatures ◽  
Kinetics Of

X-ray Photoelectron Spectroscopy (XPS) has been used to investigate the oxidation of (011) Ge substrates. The sample surfaces were CP4-etched, then annealed in situ, at different temperatures, for various durations. Dry and wet atmospheres were used. The oxidation rate during the early stage was increased by the presence of moisture in the atmosphere. A simple model was used to define and determine an apparent thickness of the oxide film from XPS measurements. The time dependence of the apparent thickness is consistent with a partial coverage of the surface by oxide islands. The growth kinetics of the oxide islands obeys a nearly cubic law.

scholarly journals Photocatalytic Degradation of Estriol Using Iron-Doped TiO2 under High and Low UV-Irradiation

2018 ◽  
Author(s):  
Irwing M. Ramírez-Sánchez ◽  
Erick R. Bandala
Keyword(s):  
Photocatalytic Activity ◽  
Electron Microscope ◽  
Uv Irradiation ◽  
Photoelectron Spectroscopy ◽  
Diffuse Reflectance Spectroscopy ◽  
Bet Surface Area ◽  
Doped Tio2 ◽  
X Ray ◽  
Transmission Electron ◽  
Iron Doped

Iron Doped TiO2 nanoparticles (Fe-TiO2) were synthesized and photocatalitically investigated under high and low fluence values of UV-radiation. The Fe-TiO2 physical characterization was performed using X-ray Powder Diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM), Diffuse Reflectance Spectroscopy (DRS), and X-Ray Photoelectron Spectroscopy (XPS) technique. The XPS evidenced that ferric ion (Fe3+) was in the lattice of TiO2 and co-dopants no intentionally added were also present due to the precursors of the synthetic method. The Fe3+ concentration played a key role in the photocatalytic generation of hydroxyl radical (•OH) and estriol (E3) degradation. Fe-TiO2 materials accomplished E3 degradation, and it was found that the catalyst with 0.3 at. % content of Fe (0.3 Fe-TiO2) enhanced the photocatalytic activity under low UV-irradiation compared with no intentionally Fe-added TiO2 (zero-iron TiO2) and Aeroxide® TiO2 P25. Furthermore, the enhanced photocatalytic activity of 0.3 Fe-TiO2 under low UV-irradiation may have applications when radiation intensity must be controlled, as in medical applications, or when strong UV absorbing species are present in water.

scholarly journals Fenton Degradation of Ofloxacin Using a Montmorillonite-Fe3O4 Composite

2020 ◽  
Vol 2 (1) ◽  
pp. 32
Author(s):  
Alamri Rahmah Dhahawi Ahmad ◽  
Saifullahi Shehu Imam ◽  
Wen Da Oh ◽  
Rohana Adnan
Keyword(s):  
Electron Microscope ◽  
Photoelectron Spectroscopy ◽  
High Efficiency ◽  
Solar Irradiation ◽  
Precipitation Process ◽  
Wastewater Remediation ◽  
Solution Ph ◽  
X Ray ◽  
Subsequent Degradation ◽  
Co Precipitation

In this work, FeM composites consisting of montmorillonite and variable amounts of Fe3O4 were successfully synthesized via a facile co-precipitation process. They were characterized using X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM), N2 adsorption-desorption, and Fourier transform infrared spectroscopy (FT-IR) techniques to explain the effect of Fe3O4 content on the physicochemical properties of the Fe3O4-montmorillonite (FeM) composites. The FeM composites were subsequently used as heterogeneous Fenton catalysts to activate green oxidant (H2O2) for the subsequent degradation of ofloxacin (OFL) antibiotic. The efficiency of the FeM composites was studied by varying various parameters of Fe3O4 loading on montmorillonite, catalyst dosage, initial solution pH, initial OFL concentration, different oxidants, H2O2 dosage, reaction temperature, inorganic salts, and solar irradiation. Under the conditions of 0.75 g/L FeM-10, 5 mL/L H2O2, and natural pH, almost 81% of 50 mg/L of OFL was removed within 120 min in the dark, while total organic carbon (TOC) reduction was about 56%. Moreover, the FeM-10 composite maintained high efficiency and was stable even after four continuous cycles, making it a promising candidate in real wastewater remediation.

Thermal Stablility and Oxidation Resistance of CrAlSiN Nano-Structured Coatings Deposited by Lateral Rotating Cathode Arc

2010 ◽  
Vol 447-448 ◽  
pp. 725-729 ◽  
Author(s):  
Jhun Yew Cheong ◽  
Xing Zhao Ding ◽  
Beng Kang Tay ◽  
Xian Ting Zeng
Keyword(s):  
Oxidation Resistance ◽  
Deposition Process ◽  
Surface Oxide Layer ◽  
Ambient Atmosphere ◽  
Temperature Oxidation ◽  
X Ray ◽  
Good Oxidation Resistance ◽  
Before And After ◽  
Different Temperatures ◽  
Cathode Arc

In this paper, CrAlSiN coatings are deposited by a lateral rotating cathode arc technique. The high temperature oxidation behaviors of these coatings are studied in ambient atmosphere at temperatures ranging from 800°C-1000°C for an hour. The ternary TiAlN coating is used as the benchmark in this study. The surface morphology and chemical composition of the coating samples before and after oxidation at different temperatures are analyzed by scanning electron microscopy (SEM) equipped by energy dispersive X-ray spectrometer (EDX), glow discharge optical spectrometry (GDOS) and X-ray diffraction (XRD). The CrAlSiN coatings show much better oxidation resistance than the TiAlN coatings. TiAlN starts to oxidize from 800oC and forms a complete surface oxide layer after oxidation at 1000oC for an hour. However, CrAlSiN shows a relatively good oxidation resistance below 1000oC and only is oxidized to form a thin oxide scale with a thickness of 0.3 µm at 1000oC for one hour. It is found that the oxidation of both coatings is triggered from the surface metallic droplets generated by the arc deposition process.

Oxidation Behavior of LPPS MCrAlY Coatings at High Temperature: Part I TGO Growth and β Phase Depletion

2021 ◽  
Vol 1035 ◽  
pp. 539-544
Author(s):  
Zhao Ran Zheng ◽  
Kang Yuan
Keyword(s):  
High Temperature ◽  
Early Stage ◽  
Oxidation Kinetic ◽  
Thermally Grown Oxide ◽  
Temperature Oxidation ◽  
Β Phase ◽  
Mcraly Coating ◽  
Mcraly Coatings ◽  
Diffusion Controlled ◽  
Tgo Growth

MCrAlY can be used as bond coats for thermal barrier coatings (TBCs) with good ductility and excellent resistance against high temperature oxidation and hot corrosion. The behavior of the thermally grown oxide (TGO) scale formed at the MCrAlY coatings plays a key role on the oxidation resistance. In this paper, the oxidation kinetic curves of a MCrAlY coating at 900~1000 °C were obtained by measuring the thickness of the TGO scales. The curves basically conveyed parabolic laws, indicating a diffusion-controlled mechanism of the TGO growth. The thickness of TGO was positively correlated with the consumption of β phase during the early stage of the oxidation processes. After about the half-life of the β phase consumption, the depletion of the β phase significantly accelerated, which was caused by coating-substrate interdiffusion. In addition, the microstructure of the TGO was analyzed

scholarly journals Additively Manufactured NiTi and NiTiHf Alloys: Estimating Service Life in High-Temperature Oxidation

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2104 ◽  
Author(s):  
Hediyeh Dabbaghi ◽  
Keyvan Safaei ◽  
Mohammadreza Nematollahi ◽  
Parisa Bayati ◽  
Mohammad Elahinia
Keyword(s):  
High Temperature ◽  
Oxidation Rate ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Early Stage ◽  
Niti Alloy ◽  
Temperature Oxidation ◽  
X Ray ◽  
Rate Law ◽  
Parabolic Rate

In this study, the effect of the addition of Hf on the oxidation behavior of NiTi alloy, which was processed using additive manufacturing and casting, is studied. Thermogravimetric analyses (TGA) were performed at the temperature of 500, 800, and 900 °C to assess the isothermal and dynamic oxidation behavior of the Ni50.4Ti29.6Hf20 at.% alloys for 75 h in dry air. After oxidation, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were used to analyze the oxide scale formed on the surface of the samples during the high-temperature oxidation. Two stages of oxidation were observed for the NiTiHf samples, an increasing oxidation rate during the early stage of oxidation followed by a lower oxidation rate after approximately 10 h. The isothermal oxidation curves were well matched with a logarithmic rate law in the initial stage and then by parabolic rate law for the next stage. The formation of multi-layered oxide was observed for NiTiHf, which consists of Ti oxide, Hf oxide, and NiTiO3. For the binary alloys, results show that by increasing the temperature, the oxidation rate increased significantly and fitted with parabolic rate law. Activation energy of 175.25 kJ/mol for additively manufactured (AM) NiTi and 60.634 kJ/mol for AM NiTiHf was obtained.

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