Irradiation of a pulsed Nd:YAG laser at 532 nm to gold particles of less than 50 nm in aqueous solution was
found to cause the shape change and size reduction of the particles. Typically, the nonspherical gold particles
between 20 and 50 nm in diameter disappeared, whereas the number of gold particles of spherical shape less
than 10 nm increased. The size reduction ceased after 5 min irradiation. The maximum diameter in the size
distribution decreased to ca. 10 nm when the laser fluence was increased up to nearly 800 mJ cm-2. The
temperature of the gold particles was estimated from the absorbed laser energy by the particles and was
found to rise as high as the boiling point of gold; these results were supported by the measurements of the
blackbody radiation from the particles. The shape change and size reduction are considered to occur through
melting and vaporization of the gold particles. The high temperature, which causes melting and vaporization,
is a result of the strong absorption of the laser energy by the particles and the low heat transfer to the surrounding
water.
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The mass accommodation (condensation) coefficient R of water vapor into liquid water was theoretically studied via two complementary approaches: by molecular dynamics (MD) scattering simulation and by computational fluid dynamics simulation of the droplet train/flow reactor experiment. The MD scattering simulation predicts R ∼ 1 at 273 K. The fluid dynamics simulation quantitatively interprets the gaseous resistance in the droplet train flow tube, which demonstrated that the results of the droplet train/flow reactor experiment [Li et al., J. Phys. Chem. A 2001, 105, 10627] are consistent with a value for the water R in the range between 0.2 and 1. Both methods are thus seen to be consistent and provide values for the mass accommodation coefficient of water in the ideal situation free from surface impurities and nonequilibrium latent heat production.
The influence of ion modification using rare-earth cations on crystal structures, along with the insulating and ferroelectric properties of BiFeO3 (BFO) thin films was investigated. Rare-earth-substituted BFO films with chemical compositions of (Bi1.00−xREx)Fe1.00O3 (x=0–0.15, RE=La and Nd) were fabricated on (111)Pt∕TiO2∕SiO2∕(100)Si substrates using a chemical solution deposition technique. A crystalline phase of rhombohedral BFO was obtained by heat treatment in a N2 atmosphere at 500°C for 5min. The crystal anisotropy and the Curie temperature of BFO were degraded continuously with increasing contents of La3+ or Nd3+ cations. Ion modification using La3+ and Nd3+ cations up to x=0.05 lowered the leakage current density of the BFO film at room temperature from approximately 10−3 down to 10−6A∕cm2. A polarization (P)-electrical field (E) hysteresis loop measured at 10K revealed that the intrinsic remanent polarization of La3+- and Nd3+-substituted BFO films with x=0.05 (44 and 51μC∕cm2, respectively) was smaller than that of a nonsubstituted BFO film (79μC∕cm2), which is ascribed to the degradation of crystal anisotropy and the Curie temperature of the BFO crystal.
Ion modification techniques for improving the insulating and ferroelectric properties of BiFeO 3 (BFO) thin films are reported. Rare-earth-substituted BFO films with chemical compositions of Bi 1:00Àx RE x Fe 1:00 O 3 [RE = La and Nd] were fabricated on (111)Pt/TiO 2 /SiO 2 /(100)Si substrates using a chemical solution deposition technique. Well-saturated P-E curves were obtained for La 3þ -and Nd 3þ -substituted BFO films, while the curve of a nonsubstituted BFO film was distorted due to the leakage current. Remanent polarization (P r ) values measured at 10 K were respectively 44 and 51 mC/cm 2 , for La 3þ -and Nd 3þ -substituted BFO films, which are significantly superior to conventional Pb-free ferroelectrics.
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