Papers by Keyword: Aluminium Oxide

Abstract: One candidate material for boiler components in supercritical water gasification (SCWG) processes is oxide dispersion-strengthened steels (ODS), which can resist aggressive humidified atmospheres under high pressures and temperatures. The high-temperature oxidation resistance of ODS steel can be improved by adding nanooxide particles such as Al₂O₃. In this study, the corrosion resistance of Fe-18Cr ferritic ODS steel reinforced with different nanoAl₂O₃ between 0.5-3.0 wt% in a humidified atmosphere containing 80% H₂O at 800 °C was investigated. The lump phase of chromium and nanoAl₂O₃ particles were dispersed on iron matrixes after sintering. Several pores occurred in the Fe-18Cr ODS matrix due to air entrainment during forming processes, but they decreased after reinforcing with the nanoAl₂O₃. Adding 0.5 wt% nanoAl₂O₃ decreased the porosity of the ODS steel by around 1.8 times. After the oxidation test for 10 hours, the mass gain of the ferritic ODS steel decreased by about 9 % when the nanooxide was added. Fe-Al-rich oxides were found with hematite and Fe-Cr spinel oxide layers, which increased the oxidation resistance of the ODS steel.

Abstract: The paper presents an optimization approach for enhancing the hardness and adhesion of Al₂O₃-40%TiO₂ coatings produced by High-Velocity Oxi-Fuel (HVOF) thermal spraying, aimed at their application in protecting components subjected to aggressive environments and severe mechanical stresses [1-4]. Through an experimental factorial program, key parameters of the HVOF process such as fuel flow rate, oxygen flow rate, spray distance, and powder feed rate were investigated to identify optimal conditions leading to improved mechanical performance of the deposited layers. Vickers hardness and tensile adhesion tests were utilized to evaluate the properties of the coatings. The results indicated that increasing the fuel and oxygen flow rates, coupled with reducing the spray distance, significantly increased the hardness of the coatings, achieving values up to 244 HV5. Moreover, optimizing these parameters maximized the coating-substrate adhesion, reaching values exceeding 30 MPa. Microstructural analysis using scanning electron microscopy (SEM) revealed that optimized HVOF parameters generated dense layers with low porosity and enhanced adhesion at the layer-substrate interface, thereby explaining the superior mechanical behaviors of the coatings. These findings demonstrate the capability of HVOF technology to produce Al₂O₃-40%TiO₂ layers with optimal mechanical properties, essential for applications requiring resistance to wear, impact, and corrosive environments [5-7].

Abstract: Modest channel carrier mobility in SiC-MOSFETs with NO annealed gate oxides has been the main factor hampering development of low power devices (300 – 650 V). A very fast interface trap, noted as NI, has been suggested to be the main culprit for poor inversion channel carrier mobility. The origin of the NI trap is unknown, but it is likely a property of the SiO₂ and it is enhanced during post nitridation. In this study we show that the NI trap is also detected in 4H-SiC/AlN and 4H-SiC/Al₂O₃ MIS-capacitors. Observations are done using conductance spectroscopy and capacitance voltage measurements at cryogenic temperatures. This strongly suggests that the NI trap is a property of the SiC surface and not the dielectric used to form the SiC/dielectric interface. Furthermore, a scanning transmission electron microscopy (STEM) was performed to confirm that there are no SiO₂ layers or islands present at the 4H-SiC/AlN and 4H-SiC/Al₂O₃ interfaces.

Abstract: Low weight is one of the most important factors in the design process of road and flight vehicles. The design engineers are careful with regards to the weight decrease without thinking twice about the primary strength. The composite is a lightweight material that has decent underlying properties and it is generally utilized. Fiber-supported polymer composites assumed a prevailing part for quite a while in an assortment of uses for their high explicit strength. The current work portrays the turn of events and the portrayal of another arrangement of GFRP. Experiments are carried out to study the effect of the addition of fillers by varying their percentages. The present work focus on the effect of the fillers on properties of Glass fiber epoxy laminates with aluminum oxide and magnesium hydroxide powders as the fillers. In the present work, fabrication and experimental investigation on unidirectional glass epoxy composites are carried out. Initially, glass fiber reinforced polymer laminate fabricated without filler material, hand layup followed by vacuum bagging methods are used . Then, by adding Aluminium oxide and Magnesium hydroxide as a filler material with different percentages like 5%, 10%, and 15% by weights and laminates are fabricated and experimental investigation is conducted to study their mechanical behavior. The comparative studies on the laminates are carried out and the obtained results are analyzed and those are quite interesting.

Abstract: Lubricants are commonly used in machining and energy system to reduce friction and wear within moving parts and aid in the transfer of heat. The use of lubricants enhances the overall performance and operation life of systems. Synthetic lubricants commonly used are non-biodegradable and are harmful to aquatic and land habitats. To overcome these challenges, biolubricants from vegetable and animal sources were considered as an alternative to synthetic and mineral lubricants. In this study, the esterification and transesterification processes were used to produce biolubricant from castor oil. Methanol and sulphuric acid (H₂SO₄) were used as alcohol and catalyst respectively for the acid catalysed esterification while ethylene glycol and sodium hydroxide (NaOH) were used for the transesterification process. The average biodiesel yield was 99.87%. The two-step method was deployed in the preparation of the castor nanobiolubricant. The nanobiolubricants were prepared using aluminium oxide (Al₂O₃) nanoparticles of 20 – 30 nm nominal diameter. The volume concentrations of 0.1%, 0.2%, and 0.4% were used in the preparation of the nanobiolubricants. The results showed that the addition of Al₂O₃ nanoparticles into the castor oil biodiesel altered the thermophysical properties (density, dynamic viscosity, pH, acidity, free fatty acid (FFA), flash point, and cold properties) of the biolubricants. The addition of Al₂O₃ nanoparticles reduced the acidity, flash point, and pH value of biolubricant while the cold flow property was improved. The dynamic viscosity decreased with an increase in temperature and increased as the nanoparticle concentration increased. The results were compared with the thermophysical properties of mineral oil, and from these analyses, Al₂O₃ nanobiolubricant can be successfully deployed as an alternative to synthetic and mineral lubricants in machining and energy systems. Fourier transform infrared (FTIR) and UV-Vis analyses were conducted on the castor oil, its biolubricant, and nanobiolubricants.

Abstract: Zinc oxide (ZnO) had been interested today because of their unique and good properties in electronic devices. ZnO nanostructured was synthesized via hydrothermal method by varied the pH value from 7, 8, 9, 10 and 11. The effect of different pH values from 7, 8, 9, 10 and 11 was changed the morphological, structure and optical properties. The samples characterized with Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD) and Ultraviolet- Visible (UV-Vis) spectroscopy. SEM is to observe the morphology images of ZnO nanostructure grains. XRD revealed the detail information on the crystallographic structure and phase formation of the materials. Lastly, UV-vis spectroscopy is to measure the band gap of optical semiconductor. From SEM result, it had shown that the hexagonal nanorods was obtained at pH 7 and pH 11 whereas nanorods is obtain at pH 8, 9 and 10. XRD revealed that the ZnO nanostructure exhibits the hexagonal wurtzite structure and the average crystallite size of ZnO nanoparticle was calculated. UV-Vis spectroscopy shows the absorption of ZnO and band determination from Tauc Plot relation plotter using UV-vis. The resulted show the pH values affect the nanostructure growth of zinc oxide semiconductor properties.

Abstract: In the present work, Cr-Al₂O₃ nanocomposite coatings were electrodeposited onto a copper substrate using a modified trivalent chromium electroplating bath with the addition of 80nm Al₂O₃ powder. The effects of mechanical agitation of electrodeposition bath on Al₂O₃ particles dispersion and particles embedment were studied. The Cr-Al₂O₃ nanocomposite samples were subjected to different tests to characterize their surface morphology, crystalline structure, and mechanical properties. The crystalline structure, composition and surface morphology of the deposits were studied by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and field emission scanning electron microscopy (FESEM). The corrosion resistance test was carried out by electrochemical polarization method. The microhardness was studied via Vickers Microhardness Test. The variation in the microhardness as a main property to achieve enhancement of Al₂O₃ incorporations with Cr matrix. From the EDX analysis, Cr-Al₂O₃ nanocomposite deposited at 200 rpm stirring speed showed the highest weight percentage (wt%) of alumina. The hardness results showed the Cr-Al₂O₃ composite coating has the best performance at 200 rpm stirring speed which the hardness increased 32.3 % compared to that of Cr coating. The corrosion current density (i_corr) of Cr-Al₂O₃ coating achieved highest value at 200 rpm. This result revealed that the corrosion resistance of Cr-Al₂O₃ coating decreases with increasing Al₂O₃ particles content.

Abstract: On a film of aluminum oxide (Al₂O₃) formed by electrolytic oxidation in distilled water (DW), the growth, transformation of its nanoporous structure, and the generation of electroluminescence (EL) in ketones and related compounds containing carbonyl groups were studied. For those contributing to the brightest EL – acetylacetone and methylpyrrolidone, it was found that the processes described in these electrolytes proceed with the highest intensity. Under the same electrolytes and conditions, similar processes, but with a lower intensity, proceed for A₂O₃ formed on pure aluminum. It was found that, with the external voltage, thermodynamic and geometrical parameters of the electrolytic system being constant, the brightness characteristics of the EL of the anodic Al₂O₃ are influenced by its structural organization and the electrophysical characteristics of the electrolyte surrounding the oxide film, which is proposed to be arbitrarily called “nonelectrolysis” because electrolysis products are not revealed in it.

Abstract: In this work we studied the effect of surface treatment of PET films, which are widely used in food packaging, on the adhesion value of ink layers based on polyvinyl chloride. To give high barrier properties to packaging laminates, the films used in their structure are coated with a nanolayer of aluminum oxide (AlOx). However, these films have a disadvantage associated with the low adhesion of adhesive and ink layers to the AlOx nanolayer. To eliminate this disadvantage, aluminium oxide nanolayer is additionally coated with various polymer coatings. In this work we studied the effect of a polyacrylic coating applied on top of an AlOx layer on improving the adhesion of ink layers. For PET films used in food packaging, optical and surface properties are also important. In this regard, additionally we measured surface free energy, coefficient of friction, and optical properties of the studied PET films. We also highlight the relationship of contact angles of wetting and the work of adhesion for the printing ink with the measured adhesion of ink layers.

Abstract: X-ray photoelectron spectroscopy (XPS) and Spectroscopic Ellipsometry (SE) were used to analyse the effect of oxygen plasma treatment on properties of aluminum oxide thin films. The aluminum oxide films were fabricated using a reactive sputtering system. The as-deposited films were treated with oxygen plasma powered by an RF generator. During the plasma treatment, the pressures were set at 1 x 10^-1 to 1x 10^-2 mbar, while the RF supplied powers at 100 W and 200 W. It was observed that lower plasma powers and higher pressures resulted in smoother films. The O/Al ratio of the films were found to decrease with increasing plasma powers and pressures. The thickness and refractive index of the films were significantly affected by the oxygen plasma treatment process, which could be related to the change in films’ packing density and the etching at the surface.