Search Results (4)

High-performance thermoplastics like polyetheretherketone (PEEK), with their outstanding thermal stability, mechanical properties and chemical stability, have great potential for various structural applications. Combining with additive manufacturing methods extends further PEEK usage, e.g., as a mold insert material in polymer melt processing like injection molding. Mold inserts must possess a certain mechanical stability, a low surface roughness as well as a good thermal conductivity for the temperature control during the molding process. With this in mind, the commercially available high-performance thermoplastic PEEK was doped with small amounts of carbon nanotubes (CNT, 6 wt%) and copper particles (10 wt%) targeting enhanced thermomechanical properties and a higher thermal conductivity. The composites were realized by a commercial combined compounder and filament maker for the usage in a material extrusion (MEX)-based 3D-printer following the fused filament fabrication (FFF) principle. Commercial filaments made from PEEK and carbon fiber reinforced PEEK were used as reference systems. The impact of the filler and the MEX printing conditions like printing temperature, printing speed and infill orientation on the PEEK properties were characterized comprehensively by tensile testing, fracture imaging and surface roughness measurements. In addition, the thermal conductivity was determined by the laser-flash method in combination with differential scanning calorimetry and Archimedes density measurement. The addition of fillers did not alter the measured tensile strength in comparison to pure PEEK significantly. The fracture images showed a good printing quality without the MEX-typical voids between and within the deposited layers. Higher printing temperatures caused a reduction of the surface roughness and, in some cases, an enhanced ductile behavior. The thermal conductivity could be increased by the addition of the CNTs. Following the given results, the most critical process step is the compounding procedure, because for a reliable process–parameter–property relationship, a homogeneous particle distribution in the polymer matrix yielding a reliable filament quality is essential. Full article

The main goals of this essay are to describe and make clear the philosophical implications of self-cultivation concerning the concept of inwardness and examine how it contributes to the formation of the Confucian identity. In two representative Korean Neo-Confucian debates, the Debate on Supreme Polarity between Yi Ǒnjŏk and Cho Hanbo and one of the issues in the Horak Debate about the original substance of the tranquil state (mibal) of the mind, we can see that self-cultivation plays a crucial role in establishing the Confucian identity. For example, the debate between Yi and Cho shows how to teach people to achieve an ideal Confucian character by interpreting “learning human affairs below (hahag-insa)” and “reaching the heavenly principle above (sangdal-chŏlli)” differently. The concept of inwardness is significant as well as problematic in understanding the sense of rivalry against Buddhism earlier and the Yangming School later in the intellectual history of Korean neo-Confucianism. Those who think of themselves as true followers of Confucius and Zhu Xi criticize that a subjective way of experiencing inwardness is close to Buddhism and misleads one in the pursuit of some lofty metaphysical entity without any practical concerns. Despite such a criticism, some Neo-Confucian scholars have emphasized that the original substance of the mind is the tranquility of inwardness. In this vein, we will investigate what kind of philosophical identity most Korean Neo-Confucians have embraced as their own. Their consistent argument for keeping the balance between honoring the virtues and inquiring about learning leads to the claim that the achievement of self-cultivation should contribute to making the world peaceful. Thus, the matter of inwardness often described as deliberate solitude is not so much a subjective realm like religious confession, but vivid experiences of daily life that have never been separated from the manifestation of the Way (dao). In conclusion, the core issue of the Neo-Confucian identity having a sense of rivalry against heresy aims at the matter of practice, i.e., how actively and properly one participates in transforming the world. Full article

The use of biobased thermoplastic polymers has gained great attention in the last years as a potential alternative to fossil-based thermoplastic polymers. Biobased polymers in fact offer advantages not only in terms of reduced dependence on fossil resources but they also lower the CO₂ footprint in accordance with sustainability and climate protection goals. To improve the properties of these materials, reinforcement with biobased fibers is a promising solution; however, it must be kept in mind that the fibers aspect ratio and the interfacial adhesion between the reinforcement and the matrix plays an important role influencing both physical and mechanical properties of the biocomposites. In this paper, the possibility of producing composites by injection molding, based on polybutylene succinate and ultra-short cellulosic fibers has been explored as a potential biobased solution. Thermo-mechanical properties of the composites were investigated, paying particular attention to the local micromechanical deformation processes, investigated by dilatometric tests, and failure mechanisms. Analytical models were also applied to predict the elastic and flexural modulus and the interfacial properties of the biocomposites. Good results were achieved, demonstrating the that this class of biocomposite can be exploited. Compared to pure PBS, the composites with 30 wt.% of cellulose fibers increased the Young’s modulus by 154%, the flexural modulus by 130% and the heat deflection temperature by 9%. Full article

The fabrication of transparent polycrystalline Y₃Al₅O₁₂ (YAG) is still a challenge, requiring the achievement of highly pure and fully dense, homogeneous materials. An important role is played by the powder characteristics: pure, fine and unagglomerated powders are essential for achieving full density and the required microstructural features. Keeping in mind these requirements, the aim of this work was to investigate the role of different synthesis parameters during co-precipitation, which is widely used to prepare YAG powders for transparent devices. The key role of the precipitant solution is here illustrated, by comparing the effect of aqueous ammonia (AA) versus ammonium hydrogen carbonate (AHC). This latter allowed the preparation of softly agglomerated powders, characterized by a very good sinterability. However, when AHC is used, attention should be paid to its concentration. By comparing the effect of two AHC precipitant solutions (at 0.5 M and 1.5 M, respectively), only the former one allowed the preparation of pure YAG powders, free from secondary phases. In this last condition, by using both chlorides and nitrates as YAG precursors, pressureless sintering at 1500–1600 °C/3 h gave rise to pure materials, highly dense and characterized by a fine and homogeneous microstructure. Full article