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The acoustic and vibrational properties of Mn-doped (Na1/2Bi1/2)TiO3-xBaTiO3 with x = 0.05 were investigated by using Brillouin and Raman spectroscopies and compared with those of undoped crystals. The mode frequency and the half width of the Brillouin doublet of the longitudinal acoustic mode showed more drastic changes near the dielectric maximum temperature compared to the broad and diffused changes of the undoped crystals, which indicates that Mn-doping induces polar domains larger than the typical polar nanoregions formed in undoped counterpart. The acoustic anomalies were most pronounced along the direction suggesting that the polarization fluctuations are anisotropic and largest along this direction. Temperature dependence of Raman spectra showed that there are two characteristics temperatures where mode splitting occurs due to local symmetry changes. The high-temperature anomaly was associated with the changes in the acoustic properties, while the low-temperature mode splitting was related to the dielectric anomaly near depolarization temperature.

Flame retardant epoxy is closely related to the safety of a human’s life against the surrounding fire threat. Flame retardant properties can be obtained by supplementing with additives, such as phosphorus compounds and nanomaterials, or synthesizing flame retardant monomers. The principle of improving flame retardancy is based on the capture of oxygen radicals and the formation of a char layer, which blocks flammable gases. This paper focuses on a flame retardant epoxy resin using naturally occurring tannic acid (TA) as a hardener, which is both an oxygen-radical quencher and a charring agent. TA is reacted with the commercially available diglycidyl ether of bisphenol A (DGEBA). The reaction between the epoxy ring of the DGEBA and multiple functional groups in TA is empirically demonstrated using dynamic scanning calorimetry (DSC) and Brillouin spectra. The most effective flame-retardant TA-DGEBA (TD) thermoset had an limiting oxygen index (LOI) value 46% higher than the control sample. This result sugges...

The phase transition sequence of a PbHf 0.7 Sn 0.3 O 3 single crystal was investigated by using Brillouin spectroscopy. The longitudinal acoustic mode showed three distinct changes at ∼370 K, ∼455 K and ∼495 K which corresponded to the antiferroelectric 1 → antiferroelectric 2 → intermediate → paraelectric phase transitions upon heating. The paraelectric phase was characterized by softening acoustic mode, increasing acoustic damping and the appearance of quasielastic central peaks which were observed upon approaching the phase transition temperature. The relaxation times derived from the acoustic mode anomalies and the central peak were consistent with each other and showed a slowing-down behavior. These precursor phenomena were attributed to the polar clusters having broken inversion symmetry. The substitution of Hf with Sn induced a very soft intermediate phase between the paraelectric and the antiferroelectric phases, where the longitudinal acoustic mode exhibited the lowest mode frequency along with substantially high acoustic damping. The transverse acoustic mode, which was observed in the two antiferroelectric phases, did not appear in the intermediate phase. These results indicated that the average symmetry of the intermediate phase may be cubic consisting of fine ferroelastic domains.

Pressure and molecular-weight dependences of acoustic mode behaviors of polystyrene polymeric material were investigated by using Brillouin spectroscopy. The longitudinal, the transverse and the bulk sound velocities were measured over a wide pressure range from ambient pressure to more than 10 GPa for five polystyrene polymers whose molecular weight ranging from 3700 to 979200. The longitudinal and the bulk sound velocities displayed nearly the same pressure dependence for all polystyrenes indicating that the effective free volume is very similar in five polystyrene polymers despite the huge change in the molecular weight. The Poisson's ratio slightly increased with decreasing molecular weight.

Temperature dependences of thermal, thermogravimetric, and acoustic properties were investigated for the crystalline silk fibroin films crystallized by methanol exposure. The crystallization peak in the thermal flow at ~ 225 ◦ C, which was prominent in the amorphous silk film, disappeared in the crystalline silk film. The heat-treatment at ~ 100 ◦ C for 1 h reduced the weight by ~5.5% due to the release of water molecules. The formation of beta-sheets in the film did not have any substantial effect on the acoustic properties of the longitudinal acoustic mode in the crystalline film. However, the heat treatment of the methanol-exposed silk film induced clear anomalies in the acoustic mode behaviors in a specific temperature range between −20 ~ 30 ◦ C. The existence of water molecules has more profound effect than the crystallinity does on the acoustic properties of silk fibroin films.

The acoustic properties of three polystyrene polymers with different molecular weights were investigated as a function of temperature by using Brillouin light scattering. The longitudinal sound velocity showed a change in the slope, which depended on the molecular weight, at the glass transition temperature. The absorption coefficient exhibited a maximum above the glass transition temperature, and the maximum temperature became higher as the molecular weight was increased. Comparison with previous acoustic studies on polystyrene indicate that a substantial frequency dispersion caused by strong coupling between the longitudinal acoustic waves and the segmental motions exists in the high-temperature range.

Hydrostaticity of poly(methyl methacrylate) (PMMA) loaded in a diamond anvil cell (DAC) was investigated up to ∼10 GPa under two conditions, i.e., with and without pressure-transmitting medium. When PMMA was loaded in the DAC without methanol-ethanol mixture, one of the most widely-used pressure-transmitting media, hydrostatic pressure condition was not fulfilled having a pressure gradient. However, the Brillouin frequency shift of the longitudinal acoustic mode of PMMA exhibited nearly the same pressure dependence regardless of the loading condition whether it was loaded with or without the methanol-ethanol mixture. This suggests that the equation of state (pressure-density relationship) of PMMA, which is calculated by using the Brillouin frequency shift, can be obtained reliably without any pressure medium at pressures less than the solidification pressure of the liquid.

The acoustic properties of 0.95(Na 1/2 Bi 1/2 )TiO 3 –0.05BaTiO 3 (NBT–0.05BT) single crystals were investigated in a hypersonic frequency range and compared to those of archetypal relaxor Pb(Mg 1/3 Nb 2/3 )O 3 (PMN). Temperature dependences of the Brillouin frequency shift of the longitudinal acoustic (LA) mode, as well as its half width, of NBT–5%BT and PMN exhibited diffuse and broad anomalies over a wide temperature range, which were related to the softening of the sound velocity and substantial increase in the hypersonic damping toward the dielectric maximum temperature. These broad acoustic anomalies of unpoled NBT–0.05BT suggest the existence of noncentrosymmetric polar nanoregions in the paraelectric phase which do not evolve into a long-range ferroelectric order. The calculated relaxation times of NBT–0.05BT exhibited much longer values compared to those of PMN, which suggests that the size of polar nanoregions of NBT–0.05BT is larger than that of PMN.

The elastic properties of a biocompatible silk film were investigated under temperature and pressure variations by using Brillouin spectroscopy. The Brillouin frequency shift decreased monotonically upon heating and showed a sudden change at the glass transition temperature. The existence of water molecules in the film increased the longitudinal modulus by approximately 10% and induced a relaxation peak in the hypersonic damping at ~60 ◦ C. The pressure dependences of the sound velocities of the longitudinal and the transverse acoustic modes and the refractive index were determined for the first time at pressures up to ~15.5 GPa. All these properties increased upon compression; these changes indicated that the free volume in the silk film collapsed at a pressure of about 3 GPa.

The temperature dependences of the acoustic properties and the dielectric relaxation times of polydimethylsiloxane were investigated by using high-resolution Brillouin and broadband dielectric spectroscopies. The longitudinal sound velocity showed a large increase upon approaching the glass transition temperature while the acoustic absorption coefficient exhibited a maximum at ~263 K. Comparison of these results with previous ultrasonic data revealed a substantial frequency dispersion of the acoustic properties of this silicone-based elastomer. The relaxation times derived from the acoustic absorption peaks were consistent with the temperature dependence of the dielectric relaxation time of the structural a process, indicating a strong coupling between the acoustic waves and the segmental motions of the main chains.

Acoustic anomalies of (1-x)(Na1/2Bi1/2)TiO3-xBaTiO3 (NBT-xBT) with x = 0.05 were investigated over a wide temperature range of from 900°C to −200°C by using Brillouin light scattering. The sound velocity of the longitudinal acoustic mode propagating along the [100] direction showed a substantial softening, while the acoustic attenuation coefficient of this mode exhibited a large increase in the paraelectric phase. These anomalies were attributed to the formation and growth of noncentrosymmetric polar regions in the paraelectric phase, which was supported by the appearance of the strong polarized central peak. The absence of any sharp or discontinuous changes in the acoustic properties seems to suggest that the polar regions remain short-ranged and do not form macroscopic polar domains at low temperatures, which may be attributed to the inherent A-site disorder induced by random substitutions of Bi, Na and Ba cations.

Recent environmental issues have driven the development of bioderived chemicals for new composite materials and recycling methods. This paper presents the use of tannic acid (TA)-based epoxy as a polymeric matrix for fabricating and recycling carbon-fiber-reinforced plastic (CFRP). TA plays a critical role in increasing the adhesion of the interface between a polymeric matrix and carbon fiber (CF), ultimately improving the mechanical properties of the CFRP. In addition, its char forming ability endows the CFRP with flame-retarding and smoke-suppressing properties. TA-based CFRP can be treated with supercritical deionized water (scDW) with no additives, producing carbon spheres from the degradation of the epoxy matrix and clean CFs. Each product can be applied as various materials for different purposes. In this paper, a new paradigm is suggested to fully recycle epoxy-based CFRP composites.

The acoustic properties of unpoled (Na1/2Bi1/2)TiO3-5%BaTiO3 (NBT-5%BT) lead-free single crystals were investigated over a wide temperature range from 740 °C to room temperature. Temperature dependences of sound velocities, acoustic attenuation coefficients, and independent elastic constants were determined by using Brillouin spectroscopy. Among the three symmetrized eigen elastic constants C44, (C11 − C12)/2, and C11 + 2C12, (C11 − C12)/2 was the smallest and showed the largest softening at high temperatures above the dielectric maximum temperature (Tm). The softening of (C11 − C12)/2 resulted in the substantial increase of the elastic anisotropy parameter defined as 2C44/(C11 − C12). This suggested that the local symmetry and the associated structural instability of local polar distortions were tetragonal. The onset temperature of quasistatic dynamics of polar nanoregions was ∼500 °C at which all four attenuation coefficients began to increase noticeably. The broad and diffused acoustic anomalies indicated that the low-temperature phase is a typical relaxor state without any long-range order. However, the noncubic local distortions at low temperatures seem to drive the average symmetry of NBT-5%BT to deviate from the cubic phase because the premise of three independent elastic constants for the ideal cubic phase was no longer valid below Tm.

The elastic properties of lead-free (Na1/2Bi1/2)TiO3-BaTiO3 single crystals near the morphotropic phase boundary were investigated by using Brillouin spectroscopy at room temperature. The measured longitudinal elastic constants of unpoled single crystals with a BaTiO3 content of 5% exhibited large changes depending on the scattering geometry, indicating that a substantial acoustic dispersion effect exists in this system. This was attributed to the relaxor nature due to inherent disorder in the A-site of the perovskite structure.

Acoustic properties of antiferroelectric (AFE) PbZr0.72Sn0.28O3 single crystals were investigated in a wide temperature range by Brillouin light scattering spectroscopy. The Brillouin frequency shift of the longitudinal acoustic (LA) mode exhibited three abrupt changes corresponding to the successive phase transitions between the paraelectric, intermediate, antiferroelectric (AFE2) and antiferroelectric (AFE1) phases upon cooling. The change in the LA mode frequency and the damping maximum of PbZr0.72Sn0.28O3 were much higher than those of pure PbZrO3. This was attributed to enhanced polarization fluctuations caused by increased ferroelectric distortions due to Sn substitution and the proximity to the tricritical point on the phase diagram of PbZr1-xSnxO3.

The acoustic properties of biaxially-oriented polyethylene terephthalate (PET) were investigated as a function of either temperature or pressure by using Brillouin spectroscopy. The Brillouin frequency shift of the longitudinal acoustic mode of both biaxially-oriented and amorphous PET materials showed a change in the slope near 80 °C, which was the approximate glass transition temperature. The acoustic damping of amorphous PET exhibited large values near the melting temperature compared to that of semicrystalline PET. This indicated stronger coupling between the acoustic waves and the structural relaxation process in the amorphous state. The pressure dependences of the sound velocities were investigated at pressures up to 8.5 GPa by using a diamond anvil cell. The pressure-density relationship could be obtained based on the Birch-Murnaghan equation of state.

We performed terahertz time-domain spectroscopy on glassy glucose, and successfully detected the boson peak, which is a universal feature of glassy materials. In addition, we have experimentally determined the infrared-vibration coupling coefficient (C IR (v)) using the vibrational density of states. The obtained C IR (v) shows linear frequency-dependence and the behavior deviates from the inorganic glass e.g. silica glass. In the temperature dependence, the complex dielectric spectra showed thermal hysteresis below about 240 K, which might be attributed to confined water molecules.

The polyethylene terephthalate (PET) substrate is one of the key materials comprising optical films, which are essential components in various optical devices, such as displays. The elastic properties of oriented PET were investigated via Brillouin light scattering spectroscopy. The high-frequency longitudinal and transverse sound velocities in the hypersonic region were determined using a special right-angle scattering geometry, where the information of the refractive index was not included in the calculation. When the propagation direction of the acoustic modes was changed in the plane with respect to the stretching directions, the longitudinal and transverse sound velocities exhibited periodic modulations, clearly revealing the acoustic anisotropy of the film arising from the stretching condition.

Antiferroelectric PbHf0.975Sn0.025O3 single crystals were studied at room temperature by Raman scattering at pressures up to 16 GPa using a diamond anvil cell. Two phase transitions were found to take place at pressures near 3 and 9 GPa, respectively, as revealed by subtle changes in Raman spectral features. A soft mode was observed at the pressure-induced phase transition occurring at 9 GPa. At pressures above ∼14 GPa, the Raman peaks become very weak and the background scattering becomes very strong. The characteristic parameters of the Raman structures were determined throughout the whole phase transitions sequence.

Background This study investigated the overall status of diabetes control and screening for diabetic microvascular complications in patients with type 2 diabetes mellitus attending primary care clinics in Korea. Methods In this cross-sectional observational study, 191 primary care clinics were randomly selected across Korea from 2015 to 2016. In total, 3,227 subjects were enrolled in the study. Results The patients followed at the primary care clinics were relatively young, with a mean age of 61.4±11.7 years, and had a relatively short duration of diabetes (mean duration, 7.6±6.5 years). Approximately 14% of subjects had diabetic microvascular complications. However, the patients treated at the primary care clinics had suboptimal control of hemoglobin A1c levels, blood pressure, and serum lipid levels, along with a metabolic target achievement rate of 5.9% according to the Korean Diabetes Association guidelines. The screening rates for diabetic nephropathy, retinopathy, and neuropathy within the past 12 months were 28.4%, 23.3%, and 13.3%, respectively. Conclusion The overall status of diabetes management, including the frequency of screening for microvascular complications, was suboptimal in the primary care clinics. More efforts should be made and more resources need to be allocated for primary care physicians to promote adequate healthcare delivery, which would result in stricter diabetes control and improved management of diabetic complications.

Brillouin spectroscopy has been widely used for the investigation of acoustic properties of condensed matters in the hypersonic region. A high-pressure Brillouin spectrometer was set up by combining a diamond anvil cell and a tandem multi-pass Fabry-Perot interferometer. It was successfully applied to liquid ethanol, and the pressure dependence of the sound velocity, the refractive index and other acoustic properties were derived based on the measurements. The detailed optical setup and experimental procedure are described.

The elastic properties of unpoled and prepoled (Na1/2Bi1/2)TiO3-xBaTiO3 (NBT-xBT) single crystals near the morphotropic phase boundary were investigated as a function of temperature using Brillouin light scattering. The acoustic mode frequency and the related acoustic damping of unpoled NBT-xBT showed very broad minimum and maximum, respectively, consistent with typical relaxor behaviors. The frequency softening of the longitudinal acoustic mode together with the increase in acoustic damping was largest along the &lt, 100&gt, direction, indicating that polarization fluctuations were most substantial along this crystallographic direction. The difference in acoustic behaviors between the unpoled NBT-xBTs with x = 0.05 and 0.08 were negligible, which means that the NBT-xBT system exhibits typical relaxor properties over a certain composition range of at least 5~8%. The obtained relaxation time of polar nanoregions in the paraelectric phase showed a gradual slowing-down character without any critical divergent behavior. The prepoling of NBT-xBT along the &lt, direction induced drastic changes in both mode frequency and damping at ~110 &deg, C when the poling field was larger than 1.4 kV/mm, corresponding to the depoling process from macroscopic/mesoscopic ferroelectric order to ergodic relaxor state upon heating. Phase coexistence of ferroelectric and relaxor states was observed at the intermediate poling field of 1.4 kV/mm.

PbHfO(3) is investigated theoretically and experimentally with respect to possible precursor effects starting in the paraelectric phase far above the cubic to tetragonal phase transition temperature. The theoretical modeling within the polarizability model predicts a giant softness of the system with spatially large polar and antiferrodistortive domain formation which compete with each other. These predictions are substantiated by the experiments, where the softness and the precursor effects are confirmed by birefringence, dielectric permittivity measurements and elastic properties by Brillouin scattering. The intermediate phase is found to have the polar nature confirmed by P-E hysteresis loop measurements, which is another manifestation of the competition between interrelated instabilities, namely a polar one and an antiferroelectric one.

We performed terahertz time-domain spectroscopy, low-frequency Raman scattering, and Brillouin light scattering on vitreous glucose to investigate the boson peak (BP) dynamics. In the spectra of $\ensuremath{\alpha}(\ensuremath{\nu})/{\ensuremath{\nu}}^{2}$ $\mathrm{[}\ensuremath{\alpha}(\ensuremath{\nu})$ is the absorption coefficient], the BP is clearly observed around 1.1 THz. Correspondingly, the complex dielectric constant spectra show a universal resonancelike behavior only below the BP frequency. As an analytical scheme, we propose the relative light-vibration coupling coefficient (RCC), which is obtainable from the combination of the far-infrared and Raman spectra. The RCC reveals that the infrared light-vibration coupling coefficient ${C}_{\mathrm{IR}}(\ensuremath{\nu})$ of the vitreous glucose behaves linearly on frequency which deviates from Taraskin's model of ${C}_{\mathrm{IR}}(\ensuremath{\nu})=A+B{\ensuremath{\nu}}^{2}$ [S. N. Taraskin et al., Phys. Rev. Lett. 97, 055504 (2006)]. The linearity of ${C}_{\mathrm{IR}}(\ensuremath{\nu})$ might require modification of the second term of the model. The measured transverse sound velocity shows an apparent discontinuity with the flattened mode observed in the inelastic neutron scattering study [N. Violini et al., Phys. Rev. B 85, 134204 (2012)] and suggests a coupling between the transverse acoustic and flattened modes.

We report on structural, electrical, and Raman investigations of phase changes induced in P(VDF-TrFE) films by electron beam irradiation. With increasing electron beam dose, the ferroelectric β-phase is weakened because of reductions in the coercive field, remnant polarization, and Curie temperature. Finally, highly dosed (9.38 × 1016 cm−2) P(VDF-TrFE) shows a paraelectric α-phase. A Vogel-Folcher type relaxor behavior becomes strong with the decreasing freezing temperature and the increasing activation energy. From the Raman scattering measurement, we observed that both the α- and the β-phases coexist irrespective of the electron beam irradiation and that the temperature dependences of the α- and β-phases are quite different. The ratio of the intensity of the α-phase to that of the β-phase sharply increases at a certain temperature, at which polar nanoregions may disappear.