Abstract:The isothermal curing process of two photopolymers were studied using micro-Brillouin spectroscopy, which is a powerful tool for probing the local elasticity of condensed matters. The Brillouin frequency shift and the half width of the longitudinal acoustic mode showed significant changes during curing under ultraviolet (UV) irradiation, and became saturated after complete curing. These were closely correlated with the changes in the optical characteristics of the white light-emitting diodes, where the same ph… Show more
“…A conventional photon-counting system combined with a multichannel analyzer (1024 channels) was used to detect and average the signal. The details of the experimental setup can be found elsewhere [59,60].…”
The nature of precursor phenomena in the paraelectric phase of ferroelectrics is one of the main questions to be resolved from a fundamental point of view. Barium titanate (BaTiO3) is one of the most representative perovskite-structured ferroelectrics intensively studied until now. The pretransitional behavior of BaTiO3 single crystal grown using a solid-state crystal growth (SSCG) method was investigated for the first time and compared to previous results. There is no melting process in the SSCG method, thus the crystal grown using a SSCG method have inherent higher levels of impurity and defect concentrations, which is a good candidate for investigating the effect of crystal quality on the precursor phenomena. The acoustic, dielectric, and piezoelectric properties, as well as birefringence, of the SSCG-grown BaTiO3 were examined over a wide temperature range. Especially, the acoustic phonon behavior was investigated in terms of Brillouin spectroscopy, which is a complementary technique to Raman spectroscopy. The obtained precursor anomalies of the SSCG-grown BaTiO3 in the cubic phase were similar to those of other single crystals, in particular, of high-quality single crystal grown by top-seeded solution growth method. These results clearly indicate that the observed precursor phenomena are common and intrinsic effect irrespective of the crystal quality.
“…A conventional photon-counting system combined with a multichannel analyzer (1024 channels) was used to detect and average the signal. The details of the experimental setup can be found elsewhere [59,60].…”
The nature of precursor phenomena in the paraelectric phase of ferroelectrics is one of the main questions to be resolved from a fundamental point of view. Barium titanate (BaTiO3) is one of the most representative perovskite-structured ferroelectrics intensively studied until now. The pretransitional behavior of BaTiO3 single crystal grown using a solid-state crystal growth (SSCG) method was investigated for the first time and compared to previous results. There is no melting process in the SSCG method, thus the crystal grown using a SSCG method have inherent higher levels of impurity and defect concentrations, which is a good candidate for investigating the effect of crystal quality on the precursor phenomena. The acoustic, dielectric, and piezoelectric properties, as well as birefringence, of the SSCG-grown BaTiO3 were examined over a wide temperature range. Especially, the acoustic phonon behavior was investigated in terms of Brillouin spectroscopy, which is a complementary technique to Raman spectroscopy. The obtained precursor anomalies of the SSCG-grown BaTiO3 in the cubic phase were similar to those of other single crystals, in particular, of high-quality single crystal grown by top-seeded solution growth method. These results clearly indicate that the observed precursor phenomena are common and intrinsic effect irrespective of the crystal quality.
“…The elongation was the lowest at the curing time of 8 s; all other cases exhibited similar values. 28 The measured crease recovery did not exhibit a tendency according to the curing time, but the 95% confidence interval estimation result confirmed that the numerical difference is insignificant, owing to the small range of error limits. However, the 3DP textile exhibited a low strength at the curing time of 8 s. The material was harder at 16 s (or after a longer time) and a fracture occurred during the experiment, thus disabling the measurement of the crease recovery.…”
Section: Effects Of Curing Timementioning
confidence: 75%
“…The elongation was the lowest at the curing time of 8 s; all other cases exhibited similar values. 28 Figure 4.(a) Tensile strength, elongation, and (b) crease recovery of the three-dimensional printed (3DP) textile obtained with various curing times (3D printing conditions: sample A, curing time of the burn-in layer: 45 s; layer thickness: 10 µm; post-treatment: ethanol; sample sizes: 70 × 110 mm 2 ).…”
This study aimed to produce fabrics by the digital light processing (DLP) three-dimensional (3D) printing technology and using a polyurethane acrylate photopolymer as the printing material. The effect of the acrylate oligomer concentration on printing was evaluated. The DLP 3D printing conditions, such as the curing time and layer thickness, were controlled considering the physical properties, such as the tensile strength, elongation, and crease recovery of the 3D printed material. The optimal printing conditions were as follows: concentration of acrylate oligomer in the photopolymer: 10% (v/v); curing time per layer: 14 s; and layer thickness: 100 µm. These results are expected to guide further studies on the development of fabrics using DLP 3D printing technology.
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 <100> 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 <100> direction induced drastic changes in both mode frequency and damping at ~110 °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.
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