Papers by Keyword: Ceramics

Abstract: Alumina (Al₂O₃) is a technical ceramic widely selected for demanding applications due to its excellent material properties, such as high strength, corrosion resistance, and thermal stability. In this study, the effect of the sintering temperature of 3D-printed alumina to its surface characteristics and its subsequent performance as a copper-metallized ceramic substrate was investigated. Green parts of alumina samples were prepared using stereolithography (SLA) 3D printing, debound, then sintered at temperatures ranging from 1660°C to 1740°C. Surface roughness was quantified using Atomic Force Microscopy (AFM), while the copper layer's adhesion was assessed via tape and burnishing tests. Electrical conductivity was measured with a four-point probe. A non-monotonic relationship between sintering temperature and surface roughness was observed. Roughness (Ra​) decreased as temperature increased from 1660°C to 1720°C, attributed to enhanced densification. However, increasing the temperature to 1740°C led to grain coarsening and a slight increase in roughness due to excessive grain growth. Stronger copper adhesion was achieved on smoother surfaces produced at optimized sintering temperatures. Electrical conductivity was also determined with a minimum sheet resistance of 0.089 mΩ/sq achieved.

Abstract: Irradiation of materials in space or nuclear applications is unavoidable and it is well known that it modifies their properties (electronic, optical, thermal, mechanical, ..) due to the formation of point and complex defects (vacancies Vs, self-interstitial atoms SIAs, cavities, bubbles, dislocation loops, dislocation lines, precipitates). As this review shows, irradiation can also be very useful for intentionally optimizing material properties and, when performed under very well controlled conditions, for understanding defects properties and their impact on large-scale material properties. Knowledge of how damage is created and accumulated in materials is needed to better understand the behavior of materials under irradiation, in particular their radiation resistance for nuclear applications or to know the best irradiation conditions for optimizing their properties in electronic or optical applications. Experimental characterization of damage is an essential element in achieving this objective, and is very often coupled with simulation. This paper presents general information on the introduction of damage during irradiation of materials and various examples illustrating the typical advantages of the Positron Annihilation Spectroscopy (PAS) technique for the study of radiation damage.

Abstract: In today's changing times, more and more people will use automobiles to get around, and this will consume a lot of natural resources to supply cars, in order to make energy efficiency, reducing the overall weight of the automobile is a direct way to reduce the weight of the automobile, and we need to use materials that can make the weight lighter while maintaining a certain level of strength. This review paper explores the properties of five custom materials: aluminum alloys, magnesium alloys, titanium alloys, carbon fiber, and ceramics. By comparing specific strengths and fatigue resistance, researchers found that customizing aluminum alloy are the most suitable materials for improving energy efficiency and reducing total vehicle weight, while still maintaining a certain level of stiffness. According to the data on the specific strength and fatigue resistance of aluminum alloy, it reaches conclusion that custom aluminum alloys can be used in the design of automotive vehicles as a function of improving fuel efficiency by reducing weight.

Abstract: AM technologies have been developed for different applications in sectors such as aeronautics, automotive, or healthcare. Additionally, the range of materials that can be 3D printed has increased considerably since these technologies began to be used in the 80s of the XX^th century. Nowadays, it is possible to use both polymers and composite materials (ceramic-filled, metal-filled, etc.) in extrusion technologies, both with fused filament fabrication (FFF) and with direct ink writing (DIW). Unfortunately, even though 3D printing technologies offer much more freedom than conventional manufacturing technologies (molding, machining, etc.), before printing it is necessary to optimize the process, regarding the printing parameters that are recommended with each material. In addition, post-processing techniques are often required. This study aims to show not only the different parameters that are to be considered to optimize material extrusion 3D printing of ceramic materials, mainly regarding dimensional accuracy and surface finish, but also the types of structures that can be manufactured, as well as the challenges that are nowadays faced regarding 3D printing of ceramics.

Abstract: This work presents the investigation of nanopowders from magnesium aluminum spinel doped with Cr³⁺. Different synthesis conditions were used to determine the influence on lattice parameter. The following synthesis parameters varied: time of calcination, cold pressing and alternative precursor of Cr³⁺. The nanopowders properties were measured by XRD, optical transmission and EDX spectroscopy. The determined average size of synthesized nanoparticles is around 70 nm. Ceramic samples are given by hot pressing and studied by transmission spectroscopy and luminescent spectroscopy. The excitation and emission spectra demonstrates ²E - ⁴A₂ (687 nm), ⁴A₂ - ⁴T₁ (400 nm) and ⁴A₂ - ⁴T₂ (532 nm) transitions.

Abstract: Fired bricks have shown tremendous potential as a construction material due to their properties. However, their use required some specifications in terms of quality, resistance, and durability. In developing countries, the lack of tools to make test specimens leads to many defects in these brick specimens responsible for low durability and weak precision during mechanical tests and shrinkage. In this study, a simple and traditional method of making test bricks is presented. This simple method allows the production of bricks with the required properties. This method is especially efficient for semi-soft consistency pastes. The elaborated handmade pastes present a very different particle-size distribution < 2 mm (clay: 18-66%; silt: 12-53%; sand: 5-65%). The pastes do not stick to the walls of the mould like in the case of steel moulds, and it gives specimens with standard shape, smooth surface, and sharp edges. The resulting fired bricks exhibit high mechanical strength (up to 102 MPa for the compressive strength, and up to 28 MPa for the flexural strength) comparable to and even better than those of conventional methods. The elaborated bricks allowed also the measurement of very important parameters such as drying and firing shrinkage, drying, and firing weight loss, and porosity.

Abstract: In this study, the corrosion protection behavior of fumed SiO₂ reinforced epoxy composite coatings applied on steel substrates was evaluated and compared to graphene-epoxy nano-composite coatings. Graphene-epoxy nano-composite coatings provide excellent corrosion protection but the uniform dispersion of graphene in polymer solvent is a challenge. So, the fumed silica was chosen as the reinforcement rather than graphene. Fumed silica was treated with stearic acid and used with epoxy to get hydrophobic and corrosion resistant coatings. The partial carburization of epoxy was carried out to get carbon layer on steel substrate. The epoxy was cured at various temperatures (200, 250 and 300 °C) to see its effect on hydrophobicity and corrosion behavior of the composite coatings. Presence of different functional groups of modified silica and epoxy was confirmed by FTIR ATR. Coating prepared from this material was evaluated microscopically with respect to structure, uniformity and interface with optical microscope. Polarization effect of coatings was studied by potentiodynamic polarization method. Coating thickness was measured by an Elcometer gauge, and these were checked by the micrographs at 50, 200 and 1000x. E250 (60% epoxy + 6% Silica) showed corrosion rate of 0.017mpy much lower than uncoated steel substrate (2.612mpy). Contact angles for npc200 (neat partially carburized epoxy cured at 200°), 4Si70 (60% epoxy+4% Silica cured at 70°), 6Si300 (60% epoxy+6% Silica cured at 300°) and 6Si250 (60% epoxy+6% Silica cured at 250°) were 90°, 89.5°, 72.5° , 97.5° respectively. So, it was proved that partially carburized epoxy coating with 6% modified silica cured at 250 °C was more corrosion resistant and hydrophobic in nature.

Abstract: The article presents the results of a single grain scratching simulation of a ceramic workpiece using the smoothed particle Galerkin method. The studies were carried out for 0.1-0.8 μm depths of cut, matching the ductile-brittle transition of ceramics grinding with minimum subsurface damage. The crack depth and scratching force were obtained for scratching speed of 40-140 m/s.

Abstract: The article considers the issues of tribological properties of a titanium alloy when sliding without lubrication on zirconium ceramics. The coefficients of friction and wear resistance of friction pairs are investigated in relation to conditions in which it is impossible to use liquid lubricants. The statement about the possibility of normal operation of a pair of titanium - zirconium ceramics at a temperature of 150 ° C and more is substantiated. It is shown that the working capacity of a friction pair can be ensured by alphanizing the friction surface. Taking into account that titanium alloys are widely used in aircraft engine technology, special attention is paid to the coefficient of friction, because a high value can lead to failure of the friction unit. On the basis of the study, the application perspectiveness of zirconium ceramic materials for increasing the reliability and service life of friction units operating without lubrication at elevated temperatures in contact with a titanium alloy have been established.ds.

Abstract: An urgent task in the field of creating new functional oxide materials is to obtain products with specified properties for specific requirements, which will expand the field of application of such materials in practice. The result of work on this problem will be discussed. The paper presents the results of obtaining and studying the structure and properties of nickel-zinc ferrites doped with cobalt, with the general formula Ni_0.3Zn_0.7-xCo_xFe₂O₄ (with the substitution x equal to 0; 0.1; 0.3; 0.5). The samples were obtained by solid-phase synthesis in a tube furnace with silicon carbide heaters at a temperature of 1150 °C. The porosity of the materials obtained was calculated. For porous ceramic materials, it is one of the quality criteria.