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This article presents the study of the rheological properties and the printability of produced ceramic-polymer filaments using fused deposition method (FDM) 3D printing technology. Powder mixtures with an alumina content of 50 to 70 vol.% were fabricated by a wet processing route. A series of rheological experiments of the obtained mixtures were conducted in the temperature range from 200 to 220 °C for the commercial polylactide (PLA) powder and from 200 to 240 °C for ceramic-polymer, which corresponds to the recommended temperatures for 3D printing of commercial PLA filaments. The composition with the maximum content of alumina leads to a powdery material in which the molten polymer is insufficient to measure the rheological properties. In spite of this, the filaments were prepared from all the obtained mixtures with a tabletop single-screw extruder, the diameter and surface profile of which were analyzed. As the ceramic content increased, the diameter and surface roughness of the filaments increased. Therefore, it was only possible to print an object from a filament with the lowest ceramic content. However, the print quality of the 3D printed objects from the fabricated ceramic-polymer filament is worse (imperfect form, defects between layers) compared to the commercial PLA filament. To eliminate such defects in the future, it is necessary to conduct additional research on the development of printing modes and possibly modify the software and components of the 3D printer. [ABSTRACT FROM AUTHOR]

The main goal of the present work was to synthesize a composite consisting of h-BN particles coated with a γ-Al2O3 nanolayer. A method was proposed for applying nanocrystalline γ-Al2O3 to h-BN particles using a sol–gel technique, which ensures the chemical homogeneity of the composite at the nano level. It has been determined that during crystallization on the h-BN surface, the proportion of spinel in alumina decreases from 40 wt.% in pure γ-Al2O3 to 30 wt.% as a result of the involvement of the B3+ ions from the surface nitride monolayers into the transition complex. For comparison, nano-alumina was synthesized from the same sol under the same conditions as the composite. The characterization of the obtained nanostructured powders was carried out using TEM and XRD. A mechanism is proposed for the formation of a nanostructured γ-Al2O3@h-BN composite during the interaction of Al-containing sol and h-BN suspension in aqueous organic media. The resulting composite is a promising model of powdered raw materials for the development of fine-grained ceramic materials for a wide range of applications. [ABSTRACT FROM AUTHOR]

Machining is an indispensable manufacturing process for a wide range of engineering materials, such as metals, ceramics, and composite materials, in which the tool wear is a serious problem, which affects not only the costs and productivity but also the quality of the machined components. Thus, the modification of the cutting tool surface by application of textures on their surfaces is proposed as a very promising method for improving tool life. Surface texturing is a relatively new surface engineering technology, where microscale or nanoscale surface textures are generated on the cutting tool through a variety of techniques in order to improve tribological properties of cutting tool surfaces by reducing the coefficient of friction and increasing wear resistance. In this paper, the studies carried out to date on the texturing of ceramic and superhard cutting tools have been reviewed. Furthermore, the most common methods for creating textures on the surfaces of different materials have been summarized. Moreover, the parameters that are generally used in surface texturing, which should be indicated in all future studies of textured cutting tools in order to have a better understanding of its effects in the cutting process, are described. In addition, this paper proposes a way in which to classify the texture surfaces used in the cutting tools according to their geometric parameters. This paper highlights the effect of ceramic and superhard textured cutting tools in improving the machining performance of difficult-to-cut materials, such as coefficient of friction, tool wear, cutting forces, cutting temperature, and machined workpiece roughness. Finally, a conclusion of the analyzed papers is given. [ABSTRACT FROM AUTHOR]

Spray drying is a widely used method of converting liquid material (aqueous or organic solutions, emulsions and suspensions) into a dry powder. Good flowability, narrow size distribution, and controllable morphology are inherent in powders produced by spray drying. This review considers the granulation factors that influence the final properties of the silicon nitride dried powders. The first group includes the types of atomizers, manifolds, and drying chamber configurations. The process parameters fall into the second group and include the following: inlet temperature, atomizing air flow, feed flow rate, drying gas flow rate, outlet temperature, and drying time. Finally, the last group, feedstock parameters, includes many factors such as feed surface tension, feed viscosity, solvent type, solid particle concentration, and additives. Given the large number of factors affecting morphology, particle size and moisture, optimizing the spray drying process is usually achieved by the "trial and error" approach. Nevertheless, some factors such as the effect of a solvent, dispersant, binder, and sintering additives considered in the literature that affect the Si3N4 granulation process were reviewed in the work. By summarizing the data available on silicon nitride powder production, the authors attempt to tackle the problem of its emerging demand in science and industry. [ABSTRACT FROM AUTHOR]

Potential relations of tribological characteristics of aluminum antifriction alloys with their compositions and mechanical properties were investigated. In this regard, the properties of eight aluminum alloys containing tin from 5.4% to 11% doped with lead, copper, silicon, zinc, magnesium, and titanium were studied. Mechanical properties such as hardness, strength, relative extension, and impact strength were analyzed. Within the tribological tests seizure load and wear of material were evaluated and secondary structures were studied afterwards. The absence of a definitive correlation between tribological behavior and mechanical properties was shown. It was determined that doping tin over 6% is excessive. The seizure load of the alloys increases with the magnesium content. Secondary structures of the alloys with higher wear rates contain one order less magnesium and tin. [ABSTRACT FROM AUTHOR]