Search

SiC fibers can be obtained by the spinning, curing, and heat treatment of polycarbosilane (PCS); however, the properties of the PCS precursor must be considered to set the correct spinning conditions. Although many studies have focused on the synthesis conditions, the characterization (in particular, the structural characteristics) of PCS fibers, and the polymer itself has limitations. In this study, PCS was prepared in two steps, and the growth of the polymer with respect to the reaction conditions was analyzed. We found that PCS is formed and grown by the rearrangement and subsequent condensation reactions of polydimethylsilane (PDMS). Further, fiber formation was affected by the reaction temperature, time, and pressure. Three types of PCS were obtained under different synthetic conditions, and they were all characterized. Regardless of the structural similarity of the PCS fibers (based on the spectroscopic analysis), the polymers showed different thermal and rheological properties. Our findings will be important in improving the production of PCS fibers (and subsequent SiC fibers) with finely controlled properties.

We propose a model on the role of interdependent self-value and group opinion climate in affecting individuals’ willingness to participate in online political discussions, as well as the underlying mechanisms through which such effects may take place. We test this model in an experiment, in which participants (N = 406) with different levels of interdependent self-value read a message that promotes participation in discussions about genetically modified foods in an online group characterized by a friendly, hostile, or mixed opinion climate. Results show that those with high interdependent self-value are more likely to engage in online civic discussions via in-depth information processing of the discussion promotion messages. This central information processing was more likely to mediate the effect of interdependent self-value on willingness to discuss when individuals encountered polarized (i.e., friendly or hostile) public opinion than a neutral opinion climate.

Recently, attempts have been made to use silicon carbide (SiC) ceramics as a fuel compact in nuclear reactors. However, the use of sintering additives in the conventional sintering of SiC leads to a coarse microstructure with high porosity and large grains due to the low sinterability and the large amount of grain boundaries or a second phase, deteriorating the mechanical properties, and hence limiting widespread industrial applications. In this study, polycarbosilane (PCS) and spark plasma sintering (SPS) as the SiC precursor and sintering method, respectively, were applied to overcome the low sinterability and the use of sintering additives. As the raw material, amorphous PCS was prepared by pyrolysis at 1000 °C. To decrease the particle size, pyrolyzed PCS powder was subjected to ball milling by using high-energy ball milling. The ball-milled amorphous PCS powder was sintered by SPS. Sintering was carried out at different temperatures (i.e., 1700, 1800, and 1900 °C) and pressures (i.e., 40 and 80 MPa). After SPS, the core/rim structure of the sintered pellet was formed on account of the oxygen originating from the native oxide layer and free carbon in the PCS powder as the raw materials. In the core/rim structure comprising the core, as well as the intermediate and rim regions, the microstructure and chemistry of each region exhibited marginal difference with respect to the free carbon and oxygen. The phase fraction of α-SiC increased from the rim region to core region due to the discrepancy of actual loaded pressure on account of friction with the wall surface. The existing carbon was verified to be graphitized carbon. Owing to the short reaction time, graphitization did not completely proceed, and deficient graphitization led to graphitized carbon as not graphite. The introduced oxygen changed to amorphous SiO2, which was applied to the sintering-additive-like liquid-phase sintering.

Social networking sites are increasingly used to promote corporate social responsibility initiatives. Consumers can like, share, or comment on corporate social responsibility messages on social networking sites, signaling public approval or disapproval and affecting an individual's perceived legitimacy of the organization. Especially for controversial companies, such as alcohol brands, both perceived legitimacy of a cause and consumer purchase intention might be enhanced by expressions of public support on social networking sites. However, few studies have explored this relationship. The findings from Experiment 1 suggest that the number of followers (low vs. high) affected perceived legitimacy and purchase intention. Experiment 2 revealed that the effects of comment valence on attitudinal and behavioral intention interacted with the number of followers. These findings advance our current knowledge of factors associated with perceived legitimacy of companies that promote corporate social responsibility campaigns on social networking sites. Implications for advertising research and practice are discussed.

In this study, we prepared a perfectly ordered nacre-mimetic composite from plate-like alumina particles and epoxy resin using a rolling method. A specific feature of this method is that it progressively aligns the component particles along a single direction regardless of the product thickness at resin contents as low as 25 wt%. The obtained composite exhibited a strength as high as 200 MPa during bending. However, to examine the mechanical properties of artificial nacre, various factors such as the types of initial components and their particle sizes, contents, and orientation degrees must be considered. Hence, this study consists of two parts. The present work (which constitutes the first part) is focused on the orientation effect produced by the plate-like particles and deformation behavior of the composites observed at different orientation degrees. It was found that the obtained composite material with perfectly ordered particles exhibited pull-out behavior similar to that of natural nacre (including the crack propagation route). Further, the fracture toughness of the composite, which was higher than that of alumina, was also affected by its orientation degree.

Nacre is a natural organic-inorganic hybrid composite, whose hierarchical structure has a complex influence on its high strength. Many structural features have been discovered, which influence the mechanical properties of nacre, and the authors have a particular interest in the role of the asperities and organic-inorganic interactions. In this study, a composite was prepared which mimics the asperity structure using clay minerals. Organic-inorganic bonding was induced with silane treatment. Both factors increased the yield strength of the composites; however, different deformation behavior was exhibited. It was found that asperities improved the strength of the composite, and that composition influences the stiffness of the composite. The organic-inorganic interaction between the resin and the other components of the composite reduced the deformation of the composite and consequently improved strength.

Carbon fibers, which have excellent mechanical and thermal properties, are used in many fields; however, they are very vulnerable to oxidation and have limited service life. Various studies have attempted to address this. In this study, a SiC–C composite material was prepared using a silica sol to coat the carbon surface and improve the oxidation resistance of a carbon-fiber insulator as a material for solar-cell ingot-growing crucibles. The SiC coating was formed on the carbon surface under various conditions by controlling the composition of the silica sol, and its characteristics were examined. Via SiC-conversion coating through a carbothermal reaction, a film of thickness 30–80 nm film was uniformly formed over the entire sample. In addition, the oxidation characteristics were enhanced by a factor of three to five, when compared with conventional carbon materials.

Background: To date, much research has been conducted to measure needle manipulation quantitatively and objectively. This study was performed to quantitatively measure the differences in the amount of stimulation caused by various rotation frequencies and angles in twisting–rotating acupuncture needle manipulation. Methods: The torque Z force exerted on a tissue was measured at various rotation frequencies and angles by rotating a needle with a needle force measurement system attached to a needle insertion tissue model. Results: The results show that with rotation frequency at 60°, the torque Z force increased significantly from 0.023 N mm to 0.118 N mm as the rotation angle increased (p 0.88; p

The anterior limb of the internal capsule (ALIC), which interconnects with the frontal cortex and thalamus, is volumetrically altered in schizophrenia patients. However, it is unclear whether an abnormal ALIC volume is apparent prior to the onset of schizophrenia and whether this aberrant ALIC volume is related to the frontal gray matter in individuals at ultra-high risk (UHR) for psychosis. We used magnetic resonance imaging of 43 UHR subjects, 36 schizophrenia patients, and 42 healthy controls to investigate manually traced ALIC volumes. Additionally, we evaluated the correlation between the ALIC volume and the frontal gray matter. Significantly reduced ALIC volumes were observed in the UHR and schizophrenia groups compared to the healthy controls. However, the volume of the frontal gray matter was decreased only in the schizophrenia group. A positive correlation between the volumes in the ALIC and frontal gray matter found in healthy controls was maintained only in UHR subjects. In addition, a negative correlation between the total scores on the Positive and Negative Syndrome Scale and the ALIC volumes was observed only in schizophrenia patients. An aberrant ALIC volume but its maintained correlation with the interconnecting frontal lobe was present prior to the onset of full psychosis, indicating the prodromal phase of psychosis.

This study examines how consumers reconcile two possibly contradictory motives (public-serving and firm-serving) to the corporate social responsibility (CSR) initiatives of companies in socially stigmatized industries. Our results indicate that consumers are willing to accept and give reputational credit for firm-serving motives behind the companies’ CSR initiatives, as long as they also perceive that the companies are sincere in serving public interests (i.e., high public-serving motives). Consumers highly engaged in social causes are also willing to accept firm-serving motives when they also perceive sincere public-serving motives behind the companies’ CSR activities.