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Infrared Spectra of Internal Modes in Gd2(MoO4)3 near the Ferroelectric Phase Transition Temperature
Akira Sakai,Ken Honma 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
In order to investigate the phase transition mechanism of the improper ferroelectric Gd2(MoO4)3, we observed infrared spectra above and below the phase transition temperature with special attention to the internal modes of the MoO4 molecules. At room temperature, the crystal orientation of the single domain was determined by the angular dependence of the transmittance of the spectrum peak. At the phase transition temperature, the doubly degenerate E mode split into two modes. The degree of splitting increased with decreasing temperature. The results are compared with the results of MoO4 internal modes observed by using Raman scattering measurements.
Near-Field Raman Spectra of GMO Single Crystal
Akira Sakai,Naoto Sasaki,Takanori Ninomiya 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
In order to observe the lattice vibration in nano-scale, we have developed a new type of scanning near-eld Raman scattering system by combining scanning atomic force microscopy with microprobed Raman scattering spectroscopy. A special designed cantilever with aperture of about 150 nm in diameter was used both as an illumination nano-source and a nano-detector of scattering light. Near-eld Raman spectra of the 1 internal modes of MoO4 molecules in the GMO single crystal were observed at its cleavage surface at room temperature. The spectrum is compared with that obtained by a conventional Raman microscope. With using the piezoelectric stage, the sample was scanned in nano-scale and near-eld Raman spectra were observed as a function of position on the surface.
Raman Scattering Study of Antiferroelectric Phase Transition in Cu(HCOO)2-4H2O
Takuya Mizushima,Akira Sakai,Chikako Moriyoshi,Kazuyuki Itoh,Takeru Omura 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
Micro-Raman scattering spectra of copper formate tetrahydrate, Cu(HCOO)24H2O, were observed above and below the antiferroelectric phase transition temperature with special attention to internal modes of HCOO and H2O molecules. In the antiferroelectric phase, the symmetric stretching vibration in HCOO at 1375 cm1 splits into two modes and the degree of splitting increases with decreasing temperature. The splitting is caused by doubling of the unit cell, rather than inequivalence of the molecular site due to the reduction in symmetry. Two Ag spectra observed in b(aa)b and a(cc)a geometries show the different temperature dependence in the frequency regions of H2O symmetric stretching and C-H symmetric stretching vibrations. The dierence is discussed in terms of the two-dimensional arrangement of H2O layers in the crystal.
The Fluidity of Cement Pastes with Fly Ashes Containing a Lot of Unburned Carbon
Lee, Seung-Heun,Kawakami, Akira,Sakai, Etsuo,Daimon, Masaki The Korean Ceramic Society 2003 한국세라믹학회지 Vol.40 No.3
Fly ashes containing 6.1~16.5 wt% of unburned carbon were treated thermally at 500$^{\circ}C$ for 3 h and thus, the content of unburned carbon was decreased below 2.1 wt%, the range of particle size distribution became narrower and the mean particle size became smaller. Besides, the properties of particles in fly ashes were improved, particularly the particle shape became close to a spherical type. The fluidity of cement pastes containing fly ashes treated previously at 500$^{\circ}C$ for 3 h was increased much than that of cement pastes containing original fly ashes. When the added amount of superplasticizer was over the saturation amount, there was no correlation between the amount of unburned carbon in fly ashes and the apparent viscosity of cement pastes actually. On the contrary, when the added amount of superplasticizer was below the saturation amount, there was a correlation.
A Study on the Atomizing Mechanism for the Swirl Nozzle
Lee, Sang Woo,Sakai, Jun,Ishihara, Akira 충남대학교 농업과학연구소 1987 農業技術硏究報告 Vol.14 No.1
Two nozzles with different size (Figure 2) were particularly designed to supply air through the swirl core into the central part of the liquid stream in the same parallel direction to produce a well-mixed air and water in the whirl chamber as spray liquid in bubble formation. Atomization was attempted to improve by using both the preliminary break-up process with less viscosity and less surface tension in the whirl chamber and the effects of increased frequency of the band of drops with the raised ambient air density in front of the nozzle orifice. The volumetric ratio between spray liquid and air on four levels was used to investigate the effects of air as a component of the mixture on atomization. The results of the experiment were summarized as follows; Droplet size became progressively finer as the operating pressure was increased in the range of 0.70 kg/㎠ to 6.33 kg/㎠, which was similar to the previous works. The new atomizing mechanism so-called 'air-center nozzle' gave a narrower range in droplet size distribution with smaller volumetric median diameter (VMD) than that of the existing spray system at a given pressure, which showed the possibility of improvement of atomization in a certain limit. The volumetric median diameter produced by the new atomizing mechanism was decreased from the central region toward the exterior edges across the spray pattern.