Papers by Keyword: Aluminum Oxide

Abstract: The prospects for improving microhardness and strength characteristics of corundum ceramics (Al₂O₃) modified by zirconium dioxide (3YSZ) are investigated. Ceramic samples are molded by semi-dry pressing followed by sintering. It is experimentally established that an increase in 3YSZ content in Al₂O₃/3YSZ composite ceramics fired at temperatures above 1450 ^oC increases strength and decreases microhardness. Ceramics of optimal composition (100–x) Al₂O₃–x 3YSZ, x = 5–10 wt. % 3YSZ has high strength and hardness values, and the average value is 700MPa and 22.3±1.8 GPa.

Abstract: Al₂O₃, Al₂O₃-10%CeO₂ and Al₂O₃ – 20% CeO₂ coatings were deposited on Mg AZ91 alloy by High Velocity Oxy Fuel (HVOF) process. The microstructure of deposited coatings was characterized by scanning electron microscopy and x-ray diffraction. Nano-indentation tests were performed on deposited coatings to determine its load bearing capacity and elastic recovery. Al₂O₃ coatings exhibited coarse grain structure with porous sites. While addition of CeO₂ promoted grain refinement in the coatings. A load of 100mN was applied on all the samples for nano-indentation test. Coating with 20%CeO₂ exhibited maximum load bearing capacity of 98.7mN with elastic recovery displacement of 1000 nm.

Abstract: In this work the properties of multilayer packaging materials based on PET/AlOx film with acrylic coating were studied. Multilayer packaging materials were produced on industrial laminators using three different adhesive compositions with different content of reactive groups. It is shown that the peculiarity of the chemical nature of adhesive components affects the bond strength and the seal strength of multilayer packaging materials.

Abstract: Today 3D printing with ceramics is a promising direction in the development of additive technologies. In this work, we have developed a technology for printing with ceramic pastes based on aluminum oxide and wax, namely: an extruder for printing with ceramic pastes was modeled and manufactured, the composition of the slip was selected and the paste for printing was made. After choosing the print parameters, test samples were printed: a disk and a box. Since 3D printing with ceramics is just one of the stages of manufacturing ceramic products, then we selected the parameters for drying and sintering the raw material. Drying of products is necessary to burn off an excess amount of a binder (paraffin), and due to sintering; the raw material acquires final strength and mechanical characteristics. After sintering, the sintering parameters and physical and mechanical properties of the products were measured. The microstructure of the printed products was studied using scanning electron microscopy. The phase change during sintering was studied by X-ray analysis. All obtained properties were compared with a reference sample (corundum tile made of aluminum oxide of the same grade, but using traditional ceramic technology, including pressing, drying and sintering of the product). In terms of all properties, the printed ceramics are not significantly inferior to the reference sample; however, in general, the additive technology has more advantages, such as a wide variety of shapes, shorter manufacturing time for parts, and lower energy costs.

Abstract: This article discusses the ways of intensification of the oxidation process with the formation of surface properties necessary to increase the service life of one of the parts of an internal combustion engine - a cylinder made of cast aluminum alloy. A brief overview of existing technologies for hardening the aluminum surface is presented. Environmentally friendly options are proposed for using the potential of processes that have accumulated energy within an electrolytic cell by activating the interelectrode gap and forming an oxide with desired properties. The main difference from the existing model approaches of oxide formation lies in the parallel excitation of the main participant in the process, oxygen, in order to dominate it over other, oxygen-containing donors. Ways of using the energy of cavitation phenomena due to acoustic resonance in an electrolytic solution are proposed. Redistribution of the field potential by replacing a flat cathode with a pointed one changed the conductivity conditions in the interelectrode gap as a result of the electroconvective action. The structure of the oxide layer, phase changes, and physical properties confirming the originality of oxide coatings have been investigated.

Abstract: This article is concerned with the analysis of ordering the arrays of TiO₂ and Al₂O₃ nanotubes using the correlation-spectral methods. As the tools, the spatial Fourier spectrum and one-dimensional autocorrelation function of SEM-image have served. It was shown that the arrays of the aluminum oxide nanotubes can have a nearly ideal ordering on a small scale at the expense of two-stage anodizing. It this case, the degree of order depends also on the purity of initial aluminum and sample preparation method. The introduced characteristics can serve as the measures of the structure order-disorder sensitive to both type and degree of order as a whole and to configuration of structural elements themselves.

Abstract: This paper describes the outcomes of practical experiments in the validation of a technology for welding of the Al-Al₂O₃ metal-matrix composite material produced by the internal oxidation method. Technological capabilities are herein considered for argon-arc welding (Tungsten Inert Gas/ TIG) with filler wire and arc welding in a protective inert/active gas medium using a melting electrode (Metal Inert Gas/ MIG) for joining sheets of A6 aluminum alloy-based metal-matrix composite material (MMC). Mechanical properties of welded joints are determined and the fracture macrostructure is investigated. Fracture patterns and tensile strength are shown for different modes of welding procedure for alloy plates of 5, 8 mm in thickness by the TIG method and 25 mm by the MIG method. The macrostructural and mechanical heterogeneity of welded joints is shown. Welds made under optimal conditions are free of any macrodefects. The welded joint strength is up to 96% of the base material strength.

Abstract: This Article Presents the Results of the Development of Multilayer Ceramic Coatings to Protect Metal Products from Corrosion in Aggressive Liquid Metal Environments. the Development is Based on the Integrated Use of Low-Temperature Heterophase Transfer and Microarc Oxidation Methods. the Results of Corrosion Tests of Coatings in the Interaction with Molten Lead in the Temperature Range of 400-600°C are Presented. the Structural Characteristics of the Coatings are Considered.

Abstract: On the CCDS2000 installation, detonation spraying of coatings from M28 and METCO 6103 aluminum oxide powders on steel substrates was carried out, and the dependence of the electrical resistivity of coatings on the atmosphere humidity was studied. It is shown that when the relative humidity changes from 14 to 80%, the specific electrical resistance of the coating decreases by 2-3 orders of magnitude from ρ ˃10¹³ Ω·cm to ρ ≈ 10¹¹ Ω·cm. On the base of obtained data, the model of coating microstructure is proposed, according to which alumina layer contained through defects in a form of nanochannels with diameter in the range 1-10 nanometers. In a coating cross section, the area of nanochannels sums up to 1%. In presence of high atmospheric humidity, these nanochannels can be filled with absorbed water, increasing drasticcaly the coating electrical conductivity.

Abstract: Nowadays, nanostructures made on the basis of mixed oxides are of great interest for fundamental scientific and applied researches because of its potential applications, such as photo catalysts, luminophores, sensitive elements of gas sensors and vacuum sensors. The article describes nanostructural properties of NiO–Al₂O₃–SiO₂ prepared by sol-gel method. Nanocomposites were obtained by mixing a solution of Si (OC₂H₅)₄ (TEOS) as a SiO₂ precursor with a solution containing Al (NO₃)₃ · 9H₂O and Ni (NO₃)₂ · 6H₂O. Ethanol was used as solvent. The gel was dried at room temperature and annealed in the 100–500 °C range. The behavior of chemical bonds is considered by using FTIR technique. Crystallization of NiO phase at 500 °C is observed in XRD patterns. Aluminum atoms are incorporated into silica matrix, which was confirmed by XRD. The amorphous structures which are desirable for next generations are formed at room temperature.