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Irradiation of 9-ester-substituted anthracenes with visible light results in the formation of endoperoxides in the absence of a photocatalyst, which further undergo base-assisted fragmentation to afford anthraquinones. The excited state species of anthracene generated by energy transfer, interacts with 3O2 to afford 1O2 by energy transfer and undergoes cycloaddition with 1O2. By employing palladium(II)-catalyzed and visible light-mediated transformations, we have developed an efficient synthetic protocol for accessing diverse anthraquinones from readily available diaryl carboxylic acids. The optimal result was obtained with palladium(II) acetate, Ac-Ile-OH, benzoquinone and potassium carbonate in tert-amyl alcohol under O2 at 90 °C with irradiation from a 30 W fluorescent light bulb. [ABSTRACT FROM AUTHOR]

BN/PPS core-shell structured pellet and its composite film were primarily fabricated via a particle coating method using an adhesive layer. A thermally conductive composite was fabricated using BN-coated PPS by hot pressing. The core-shell structure did not collapse after hot pressing and formed a well-connected particle chain. Moreover, the BN/PPS composite prepared using the proposed method has a higher thermal conductivity compared to the conventional composite fabrication method, melt mixing and powder mixing, at the same filler concentration because the connected particle chain acts as a continuous heat flow channel. Moreover, the thickness of the particle layer can be controlled by controlling the viscosity of the adhesive epoxy layer using acetone as the solvent. We fabricated BN/PPS pellets with various BN layer thickness. A 1:0.3 wt ratio of epoxy and acetone has the highest thermal conductivity enhancement ratio compared to the melt mixed composite. We fabricated a composite using the hybrid method; the polymer core was prepared via melt mixing and the BN particles were coated on this core. The BN particle in the core and the outer layer has a synergetic effect, forming a 3-dimensional heat flow path, leading to outstanding thermal conductivity with a only small amount of filler. [ABSTRACT FROM AUTHOR]

Polyphenylene sulfide (PPS) is a promising material as an important engineering thermoplastic polymer for various industrial applications. Here we report a highly thermally conductive PPS composite containing boron nitride (BN) and multiwalled carbon nanotubes (MWCNTs) as a thermally conductive filler. The composite was prepared by the particle coating method into polymer pellets in order to obtain high thermal conductivity with low filler concentration, and thus overcome the drawbacks of melt mixing. A comparison between conventional melt mixing and the proposed method showed that the continuous connection of particles at the surface of each pellet led to great enhancement of thermal conductivity. Moreover, the electrically insulating BN layer effectively interrupted electron conduction, which is the major problem with using MWCNTs as a thermally conductive filler, despite their superior thermal conductivity. Our results show that the particle coating method may be used as a promising composite fabrication method for engineering plastics-based thermally conductive materials. [ABSTRACT FROM AUTHOR]

We report magnetic alignment of aluminum nitride (AlN) platelets and the outstanding material properties of its polymer composite. The magnetic property of AlN was produced by decorating the surface with strong paramagnetic iron oxide (Fe 3 O 4 ) nanospheres; the amount of iron oxide deposited is easily controlled by modulating the precursors. With the aid of iron oxide nanospheres, randomly dispersed two dimensional AlN in an epoxy matrix are successfully re-arranged in the vertical direction of the film plane by applying an external magnetic field during epoxy heat curing. Vertically aligned AlN effectively generate thermal transport channels and enhance thermal conductivity from 0.915 W/mK to 1.754 W/mK with 20 vol% filler loading which is a 1.92-fold increase at the low filler concentration compared with randomly oriented composites. The filler alignment will be a promising candidate for thermal interface material fabrication which not only significantly improves the performance, but also prevents the mechanical property degradation caused by extremely high filler loading. [ABSTRACT FROM AUTHOR]

A composite with high thermal conductivity was fabricated using anisotropic boron nitride (BN) and particle alignment techniques. Iron oxide nanoparticles introduced onto the BN surface acted as magnets that gave rise to effective particle alignment. Because of the weak interfacial affinity between filler and matrix, particles chipped during the process and the post-alignment composite had poor morphology. In order to enhance attraction at the interface, the particle surface was modified using a silane coupling agent and poly(tetramethylene glycol). The long carbon chain in the outer polymer layer became entangled with that of the epoxy matrix, resulting in enhancement of interfacial affinity and thermal conductivity. The thermal conductivity of the synthesized composite increased from 0.832 to 1.448 on 20 vol% of filler loading after particle orientation, and increased to 1.577 W/mK after polyol coating. These particle alignment and surface modifications suggest promising applications in the development of thermal interface materials. [ABSTRACT FROM AUTHOR]

In this study, anisotropic boron nitride (BN) was vertically aligned along the direction of heat transport using an external electric field. A titanium oxide (TiO 2 ) nanoparticle, which has a superior dielectric property, was deposited onto the BN surface to act as an electrically responsive material that allowed for particle alignment. Because of the relatively low dielectric property of BN, it was not observed morphological change under the electric field. After the surface modification using titanium oxide, the polarization of highly dielectric titanium oxide in the electric field led to the formation of vertical particle arrangements. The through-plane thermal conductivity of the synthesized vertically aligned composite increased from 0.78 W m −1 K −1 to 1.54 W m −1 K −1 , while through-plane thermal conductivity was decreased 1.17 W m −1 K −1 to 0.84 W m −1 K −1 , with 20 vol% filler loading. This is a 1.9-fold increase and 0.72-fold reduction compared with the conductivity of a randomly oriented composite. Moreover, this vertically aligned filler composite exhibits better mechanical properties based on the same thermal conductivity. [ABSTRACT FROM AUTHOR]

Thermally conductive BN/SiC binary filler and epoxy composite materials were fabricated via magnetic alignment. The magnetic iron oxide particles on the surface of the filler allowed particle re-orientation under the external magnetic field. Owing to its anisotropy, the vertically aligned BN composite had a high thermal conductivity and generated a vertical heat flow path. When the SiC nanoparticles were added to the binary filler, they hindered BN-particle aggregation and led to the formation of a three-dimensional heat conduction path, thereby resulting in increased thermal conductivity. The maximum thermal conductivity (5.77 W/mK) was obtained with an addition of SiC filler, and was 3.08-fold and 1.1-fold higher than that of randomly mixed BN and vertically aligned BN composites, respectively. The additional SiC–Fe 3 O 4 particles resulted in significant aggregation of the filler, which in turn led to a decrease in the thermal conductivity. The measured storage modulus of the BN–Fe 3 O 4 /SiC binary filler composite was also higher than those of the BN–Fe 3 O 4 and BN–Fe 3 O 4 /SiC–Fe 3 O 4 composites, owing to the aggregation of particles. [ABSTRACT FROM AUTHOR]

Anisotropic boron nitride (BN) was vertically aligned along the direction of heat transport using a magnetic field. Iron oxide nanoparticles deposited onto the BN surface act as a magnetically responsive material allowing particle alignment. The amount of iron oxide deposited, and therefore the magnetic response, is easily controlled by modulating the precursors. The polarization of paramagnetic iron oxide in the magnetic field leads to the formation of vertical particle arrangements. The thermal conductivity of the synthesized vertically aligned composite increased from 1.765 W m −1 K −1 to 3.445 W m −1 K −1 with 30 vol% filler loading that is a 1.96-fold increase compared with a randomly oriented composite. The filler content affected both particle dispersion and arrangements, with homogeneously dispersed fillers aggregating due to induced dipole interactions into column-like structures with favorable thermal transport properties. [ABSTRACT FROM AUTHOR]

According to the New Look theory, size perception is affected by emotional factors. Although previous studies have attempted to explain the effects of both emotion and motivation on size perception, they have failed to identify the underlying mechanisms. This study aimed to investigate the underlying mechanisms of size perception by applying attention toward facial expressions using the Ebbinghaus illusion as a measurement tool. The participants, female university students, were asked to judge the size of a target stimulus relative to the size of facial expressions (i.e., happy, angry, and neutral) surrounding the target. The results revealed that the participants perceived angry and neutral faces to be larger than happy faces. This finding indicates that individuals pay closer attention to neutral and angry faces than happy ones. These results suggest that the mechanisms underlying size perception involve cognitive processes that focus attention toward relevant stimuli and block out irrelevant stimuli. [ABSTRACT FROM AUTHOR]