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Structural, Electronic and Mechanical Properties of Perovskite Oxides LaMO<sub>3</sub> (M = Mn, Ni) Compounds in the High and Low Symmetric Phases by First Principle Calculation
摘要： The widely investigated perovskite oxides has attracted for a long time a great interest on the physical properties, in their bulk structures as well as the heterostructures components. The Lanthanum transition metal oxides LaMO3 (M= Transition metal) is part of, due to their potential use in advanced technology (including superconductivity, magnetoresistance, ionic conductivity, and a multitude of dielectric properties). Despite the broad exploration of the physical properties, we found a considerable lack in the investigation of the mechanical properties of the LaMO3 compounds. By applying the Density Functional Theory (DFT), we shed light on the structural, electronic, and especially mechanical properties of the experimentally verified phases of The LaMnO3, and LaNiO3. We first calculated the structural and electronic properties, then we continue with the single-crystal elastic constants and mechanical properties, where the bulk, shear and Young’s moduli, and the Anisotropy indexes were deduced, in order to remedy the existing gap of the theoretical knowledge about the mechanical behavior of the LaMnO3, and LaNiO3 compounds.
关键词： Density Functional Theory,Mechanical properties,Perovskite oxides,Electronic properties
更新于2025-09-23 15:23:52
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Electronic structure, mechanical and optical properties of ternary semiconductors Si <sub/>1-x</sub> Ge <sub/>x</sub> C (X?=?0, 0.25, 0.50, 0.75, 1)
摘要： The electronic structure of silicon carbide with increasing germanium content have been examined using first principles calculations based on density functional theory. The structural stability is analysed between two different phases, namely, cubic zinc blende and hexagonal phases. The zinc blende structure is found to be the stable one for all the Si1-xGexC semiconducting carbides at normal pressure. Effect of substitution of Ge for Si in SiC on electronic and mechanical properties is studied. It is observed that cubic SiC is a semiconductor with the band gap value 1.243 eV. The band gap value of SiC is increased due to the substitution of Ge and the band gap values of Si 0.75 Ge 0.25 C, Si 0.50 Ge 0.50 C, Si 0.25 Ge 0.75 C and GeC are 1.322 eV, 1.413 eV, 1.574 eV and 1.657 eV respectively. As the pressure is increased, it is found that the energy gap gets decreased for Si1-x GexC (X = 0, 0.25, 0.50, 0.75, 1). The elastic constants satisfy the Born – Huang elastic stability criteria. The bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio are also calculated and compared with the other available results.
关键词： mechanical properties,electronic structure,optical properties,First principles study
更新于2025-09-23 15:23:52
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Synthesis, In Vitro and In Vivo Behaviour of TiO2 Containing Inorganic/Organic Hybrids
摘要： In the present study inorganic/organic hybrids reinforced by introducing titanium (TiO2) in the form of Ti-n-butoxide were prepared. The phase composition, microstructure and mechanical properties of the prepared hybrids were investigated. Increasing the titanium content gradually enhanced the mechanical data of the prepared hybrids. The formation of apatite on the surface of the prepared hybrids was examined in SBF (simulated body fluid). In vivo studies revealed the ability of the hybrids to regenerate bone tissue in femur defects of adult male rabbits five months after surgery. The prepared hybrids are considered to be promising materials for bone substitutes or bone filler.
关键词： in vitro test,in vivo test,mechanical properties,inorganic/organic hybrids,microstructure
更新于2025-09-23 15:23:52
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Crack Restraining Methods and their Effects on the Microstructures and Properties of Laser Cladded WC/Fe Coatings
摘要： Laser cladded WC/Fe coatings have the advantages of low cost and high abrasion wear resistance. However, cracks always appear in WC/Fe coatings, which limits their industrial application. In this paper, the co-effects of the re-melting process, heat treatments, and amount of Co element on the cracking susceptibility, microstructures, and mechanical properties of WC/Fe laser cladding coatings were studied. Experimental results show that re-melting process is helpful to improve the surface quality of the coating and to reduce the cracking susceptibility. The hardness of the coating decreases slightly but distributes more uniformly. Cracks in the coating can be inhibited effectively by preheating the substrate to 250 ?C and maintaining the temperature during the laser cladding process, as well as applying an annealing treatment at 300 ?C for 1 h. Heat treatment also results in a slight decrease in the hardness. Crack initiation cannot be restrained completely by applying the above two methods when laser cladding a big area of coating. On the basis of the above two methods, addition of Co element to the coating can further improve its toughness and decrease the crack susceptibility. Crack-free WC/Fe coating can be manufactured when 8% Co is added, and its wear resistance is much better than that of the hardened medium steel, especially when the wear time is long.
关键词： Laser Cladding,mechanical properties,microstructures,WC/Fe coating,crack restraining methods
更新于2025-09-23 15:23:52
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A Mechanical and modelling study of magnetron sputtered Cerium-Titanium Oxide film coatings on Si (100)
摘要： Ce/Ti mixed metal oxide thin films have well known optoelectrical properties amongst several other physio-chemical properties. Changes in the structural and mechanical properties of magnetron sputtered Ce/Ti oxide thin films on Si (100) wafers with different Ce:Ti ratios are investigated experimentally and by modelling. X-ray Photoemission Spectroscopy (XPS) and X-ray diffraction (XRD) confirm the primary phases as trigonal Ce2O3 and rutile form of TiO2 with SiO2 present in all prepared materials. FESEM imaging delivers information based on the variation of grain size, the mixed Ce/Ti oxides providing much smaller grain sizes in the thin film/substrate composite. Nanoindentation analysis concludes that the pure cerium oxide film has the highest hardness value (20.1 GPa), while the addition of excess titanium oxide decreases the hardness of the film coatings. High temperature in-situ XRD (up to 1000 °C) results indicate high thermal phase stability for all materials studied. The film with Ce:Ti = 68%:32% has a new additional minor oxide phase above 800 °C. Contact angle experiments suggest that the chemical composition of the surface is insignificant affecting the water contact angle. Results show a narrow band of 87.7o to 95.7o contact angle. The finite element modelling (FEM) modelling of Ce/Ti thin film coatings based on Si(100); Si(110); silica and steel substrates shows a variation in stress concentration.
关键词： in-situ X-ray diffraction,Finite element modelling,Nanoindentation,Cerium titanium oxides,Mechanical properties
更新于2025-09-23 15:23:52
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Laser welding of electron beam melted Ti-6Al-4V to wrought Ti-6Al-4V: Effect of welding angle on microstructure and mechanical properties
摘要： Electron beam melting (EBM) is an established powder-bed additive manufacturing process for small-to-medium-sized components of Ti-6Al-4V. For further employing EBM on fabricating large-scale components, an effort has been made by joining EBM-built Ti-6Al-4V plates to wrought counterparts using laser welding, and the welding angles between EBM build direction and weld bead have been chosen as 0°, 30° and 45°. The influence of the welding angles on the microstructure, microhardness of base metals, fusion zone, and heat-affected zones, as well as the macro tensile test have been characterized. The microhardness of each zone is determined by the local microstructure, and the macro tensile properties largely depend on the EBM base metal due to the internal defects generated during the EBM process. The effect of welding angles on tensile strengths is not significant, while the elongation drops from 9.4% to 5.8% as the welding angle increases from 0° to 45°. The mechanism of stress during uniaxial tension on EBM base metal is discussed based on the stress state of columnar grains and the internal defects.
关键词： Defects,Microstructure,Mechanical properties,Additive manufacturing,Welding
更新于2025-09-23 15:23:52
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A comparative study on single-laser and multi-laser selective laser melting AlSi10Mg: defects, microstructure and mechanical properties
摘要： AlSi10Mg samples fabricated by using a multi-laser beam selective laser melting system have been studied in this paper. The relative density, defects, microstructure and mechanical properties of the isolated and overlap samples are investigated. It is found that the width and depth of the melt pools in overlap area are larger than that in isolated area, which leads to an obvious boundary between the overlap area and isolated area. Moreover, a few small pores are found in the melt pools along the overlap boundary. The isolated and overlap area in as-built samples have similar microstructure, microhardness and tensile strengths. The morphology and distribution of Si changed into particles from continuous dendrite after annealing treatment. However, it did not cause the grains to grow up. The microhardness and tensile strengths have little difference due to almost the same grain size. The slight difference in strength and elongation of isolated and overlap samples are supposed to be caused by small pores. It can be concluded that the microstructure significantly influences the microhardness and strengths of the AlSi10Mg samples, while the small pores have limited influences. There are a few smooth surfaces on the fractures of both isolated and overlap samples, which turn out to be the melt pool boundaries, indicating that the cracks mainly propagate along the melt pool boundaries.
关键词： Defects,Microstructure,Mechanical properties,Multi-laser beam,Overlap area
更新于2025-09-23 15:23:52
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Ni-P-TiO <sub/>2</sub> nanocomposite coatings with uniformly dispersed Ni <sub/>3</sub> Ti intermetallics: effects of TiO <sub/>2</sub> nanoparticles concentration
摘要： Ni-P-TiO2 nanocomposite coatings were electrodeposited on copper substrates and influence of TiO2 nanoparticles concentration on the phase structure, morphology, chemical composition, microhardness, and corrosion behaviour of the coatings was investigated. Results demonstrate that Ni3Ti intermetallics form and grow during the electrodeposition of the coatings. This study is the first to report the formation of the intermetallics in the case of electrodeposited Ni-P alloy matrix composite coatings. Moreover, the formation mechanism of the intermetallics is discussed in detail. The formed intermetallics dispersed uniformly throughout the microstructure of the nanocomposite coatings, thereby playing a critical role in improving the mechanical and corrosion-related properties of the coatings. Ni-P-10 g·L?1 TiO2 nanocomposite coating possessing the highest amount of Ni3Ti intermetallic associated with the lowest P content, thereby showing the superior microhardness and corrosion resistance. All in all, the volume fraction of Ni3Ti intermetallics is the dominant factor altering the various properties of the coatings.
关键词： corrosion behaviour,DC electrodeposition,Ni-P-TiO2 nanocomposite coatings,Ni3Ti intermetallic,mechanical properties
更新于2025-09-23 15:23:52
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Comprehensive investigation of surface quality and mechanical properties in CO2 laser drilling of GFRP composites
摘要： The present paper aims to study different laser drilling/cutting parameters including laser intensity, cutting speed, and gas pressure in order to achieve minimum surface roughness (Ra), heat-affected zone (HAZ), taper angle (TA), and maximum tensile strength (TS) of the laser-drilled glass fiber-reinforced plastic (GFRP) laminate. Full factorial design of experiment method and analysis of variance were adopted to investigate the effect of each parameter on the responses, and in addition, the surface roughness and tensile strength were compared with that of conventional drilling. The morphology of the laser-drilled holes was studied through the scanning electron microscopy (SEM). It was found that optimum laser drilling parameters can yield higher tensile strength and lower surface roughness in drilled GFRP laminate compared to the conventional drilling. Moreover, multi-response optimization was carried out on the results in order to obtain maximum tensile strength, minimum HAZ, minimum surface roughness, and minimum taper angle. The results revealed that the laser intensity, cutting speed, and assist gas pressure should be set at 2.04 W/cm2, 8 mm/s, and 4 bar, respectively, to obtain higher tensile strength and surface integrity. The results drawn from this study can be applied to improve the surface quality and mechanical properties of laser drilling of FRP materials especially in aircraft part manufacturing.
关键词： FRP,HAZ,Laser machining,Mechanical properties,Fiber-reinforced polymer composite
更新于2025-09-23 15:23:52
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Laser impact welding: Investigation on microstructure and mechanical properties of molybdenum-copper welding joint
摘要： Due to their excellent properties, molybdenum and copper are widely used in the electronics industry. However, the welding of molybdenum and copper is difficult, which limits their application prospects in the field of microelectronics devices. This paper describes a novel method for Mo/Cu welding in micro devices: laser impact welding (LIW). The experimental results found that welding improved with the increase of laser energy. The springback and interface wave in the welding area were observed by optical microscope and scanning electron microscope (SEM) and the results showed that the shapes of the interface wave were flat and zigzag. Energy dispersive spectroscopy (EDS) showed little or no diffusion of elements at the welding interface. Tensile shear test results of the welded specimens showed that there were two kinds of failure forms: solder joint failure and solder joint edge failure. The nano-hardness of the materials in the welding area increased compared with the raw materials.
关键词： Laser impact welding,Springback,Interface wave,Molybdenum,Mechanical properties,Copper
更新于2025-09-23 15:23:52