Showing papers by "Tokyo Institute of Technology published in 1973"

Pressure effects on electrical conduction in glasses

Abstract: Electrical conduction in various inorganic glasses was studied as a function of hydrostatic pressure up to 2000 atm and phenomenologically classified into electronic, ionic and mixed types. In electronically conducting glasses such as AsSe chalcogenide glasses and Fe2O3P2O5 glass, the conduction is enhanced by application of pressure. On the other hand in ionically conducting glass such as Na2OB2O3 glass, the conduction is suppressed through the concept of an activation volume. The compatibility of electronic and ionic conduction processes in glasses such as Ag-doped AsSe glasses and Bi2O3B2O3 glass, which have more complex conduction processes, was discussed from these aspects.

Total Reflection Raman Spectra; Raman Scattering due to the Evanescent Wave in Total Reflection.

Abstract: Several methods of infrared spectra have been devised for surface chemistry, including the attenuated total re­ flection (ATR) method, which was developed by Fahrenfort and by Harrick. The former calculated the relation between the reflectivities and values of the absorption coefficient at angles of incidence above the critical angle. The latter calculated the penetration depth of incident light into the optically rare medium and suggested that this method is sensitive to molecular absorption on the surface. Some workers applied the ATR methods to studies of electrode reactions in situ and adsorptions. In the infrared region water has strong absorption which is apt to disturb studies of adsorbed species. Therefore we developed a Raman spectra method corresponding to the ATR method. It observes Raman scattering due to evanescent wave in total reflection, which may be called Total Reflection Raman Spectra. We measured the de­ pendence of this intensity on the angle of incidence, which agrees with the inclination of the calculation.

Soft Modes and Superlattice Structures in NaNbO3

Abstract: From the study of superlattice reflections in X-ray diffraction, phase transitions at 365°C, 480°C, 520°C, 572°C and 643°C in NaNbO 3 are definitely identified by some distinct changes of the positions and intensities. The anisotropic diffuse X-ray scatterings have been studied with a special respect to the phase transitions. The modes of vibration which are responsible for the diffuse scatterings are found to be \(\varGamma_{25}\) and M 3 modes at R and M points, respectively. It is found from anomalous increases of the diffuse intensities that the M 3 mode condenses at 643°C and E g mode, into which two of the \(\varGamma_{25}\) mode transform, condenses at 572°C. The behaviors of the zone boundary phonons in NaNbO 3 are compared with those in KMnF 3 . The correlation of superlattice structures with the instability of the zone boundary phonons is discussed.

Anomalous Effects of a Localized Inner-Shell Hole upon Soft X-Ray Spectra in Metals. I. Generalized Power Law

Abstract: Theoretical study of Mizuno and Ishikawa on emission spectra is extended beyond the behavior precisely at threshold. Following them, the perturbation series of the spectral density functions are calculated up to the third-order term for L 23 spectra while up to the fourth-order for K, the perturbation being a static potential caused by a localized inner-shell hole that is present only before emission. In the present paper, however, the part, which goes to zero at threshold, of each of the terms is also calculated out explicitly without approximation. After rearrangement of the obtained ill-behaved perturbation series, it is found that spectral densities below threshold may be expressed in the form of a generalized power law: w (ω)=γ(ω)|ω F -ω| α(ω) . Here, ω is a frequency of emitted photon, ω F being the value at threshold. Both α(ω) and γ(ω) denote certain well-behaved functions which are regular in particular about ω=ω F .

Spontaneous Polarization Measurement in NaNO 2

Abstract: Spontaneous polarization of NaNO 2 was determined by reversing P s with a relatively low d c field of from 60 V/cm to 12 kV/cm and measuring the polarization reversal charge with an electrometer and a recorder. A clear jump in P s of 5.8 µC/cm 2 was observed at the Curie point T c . The dielectric constant e 22 in the ferroelectric phase obeys the Curie-Weiss law very well over a wide temperature range and P s is proportional to (1- T / T 0 ) 0.20±0.02 over 25°C below T c , where T 0 is the ferroelectric Curie-Weiss temperature. Below room temperature P s does not vary appreciably. The saturation polarization is estimated to be 11.9 µC/cm 2 . The electronic contribution to P s is discussed on the basis of a point-dipole approximation. It is probable that about one third of the total spontaneous polarization is contributed from the electronic polarization. The experimental technique is described in detail.

Ultrasonic Velocities in BaTiO3

Abstract: The sound velocities in BaTiO 3 has been observed near its paraelectric to ferroelectric phase transition point. The anomalous part of the sound velocity of the longitudinal wave propagating along [100] direction depends on temperature as A [( T - T 0 )/ T 0 ] -ζ with ζ=0.41 and A =1.79×10 4 cm·sec -1 where T 0 is the paraelectric temperature. The critical index ζ is close to the theoretical value of 1/2 as predicted by Dvořak. On the other hand, the velocity of the transverse wave does not show any appreciable critical behavior. The value of A is also compared with the theory given by Dvořak. The observed curve for the longitudinal wave is in good agreement with the theoretical curve, while that for the transverse wave shows a notable discrepancy.

Plastic deformation anisotropy and work-hardening of composite materials

Abstract: An energy-balance method is applied to discuss plastic anisotropy and work-hardening rate of a composite material. It is found that aligned fibers introduce a strongly anisotropic mode of plastic deformation while randomly-oriented inclusions produce isotropic plastic deformation. The hardening rate due to randomly-oriented inclusions is shown to be independent of the inclusion shape, and to be equal to that due to spherical inclusions when the elastic constants of the inclusions are the same as those of the matrix.

The crystal structure of magnesite

Abstract: The crystal structure of synthetic magnesite has been studied by X-ray and infrared methods Magnesitl is trigonal R3c, with a : 4.637 A, c : 15.O23 A, and, Z : 6. Intensity data were collected with a Rigaku automated diffractometer and MoKa radiation. The structure was refined by the fullmatrix least-squares method using anisotropic thermal parameters. The final R index for 234 teflections is 0.037. The C-O and Mg-O bond lengths were 1.283 and 2.105 A, respectively. The interatomic angles of three kinds of O-Mg-O were 88.25, 91.75 and 180.000, respectively. It is clarified that the distortion of the Mg-Oo octahedron in magnesite is smaller than that of Ca-Oe in calcite. The force constants of the Urey-Bradley force field were calculated from the infrared absorption frequencies. For magnesite the stretching force constant K : 5.41, the bending force constant II : 0.46, the repulsive force constant F : 1.97, and the force constant for the out-of-plane vibratirtn i i : o. i j -Jta. Forcalcite theyareK : 5.51,H : 0.38, F : 1.88 and fo : o.64md/A'

13C Nuclear magnetic resonance spectroscopy of polypropylene, 2. 13C spin‐lattice relaxation study in solution

Abstract: Proton-decoupled partially relaxed FOURIER transform (PRFT) NMR of 13C in natural abundance was used to determine spin-lattice relaxation times (T1) of individual carbons of polypropylene and polyethylene in o-dichlorobenzene solution and molten polyethylene. It is shown that the relaxation times of polypropylene carbons are independent of the difference in stereochemical configuration. From the values of the nuclear OVERHAUSER enhancement factor it is shown that the excess energy from equilibrium of all 13C in polypropylene and polyethylene are absorbed into lattice mainly through 13C–1H dipolar interactions. It is shown that the effective rotational motion of the skeletal carbons in polypropylene is isotropic. The activation energies of skeletal and internal methyl motions in polypropylene, separately, and skeletal motion in polyethylen in solutions were estimated from the temperature dependence of the correlation time. The assignment of the two peaks appearing in methine carbon region of polypropylene was briefly discussed. Protonenentkoppelte PRFT-NMR Spektren von naturlich vorkommendem 13C wurden zur Bestimmung von Spin-Gitter-Relaxationszeiten (T1) bestimmeter Kohlenstoffatome des Polypropylens und Polyathylens in o-Dichlorbenzol-Losung und in geschmolzenem Polyathylen verwendet. Es wird gezeigt, das die Relaxationszeiten der Polypropylen-Kohlenstoffe von Konfigurations-Unterschieden unabhangig sind. Mit Hilfe der Werte des OVERHAUSER-Verstarkungsfaktors wird gezeigt, das die Uberschus-Energie aus dem Gleichgewicht aller 13C in Polypropylen und Polyathylen vom Gitter aufgenommen wird, und zwar hauptsachlich durch 13C–1H-dipolare Wechselwirkungen. Es wird auserdem die Isotropie der effektiven Rotations-Schwingung der Kohlenstoff-Skelette im Polypropylen aufgezeigt. Die Aktivierungsenergien der Skelett- und der internen Methyl-Schwingungen im Propylen selbst und die Skelett-Schwingungen im Polyathylen in Losung wurden aus der Temperaturabhangigkeit der Korrelationszeit abgeschatzt. Die Zuordnung der beiden Peaks, die im Bereich des Methin-Kohlenstoffs von Polypropylen erscheinen, wurde kurz diskutiert.

Magnetic and Mössbauer Studies of the Ordered Perovskites Sr2Fe1+xRe1-xO6

Abstract: Structural, magnetic, electrical properties and Mossbauer effect are investigated on Sr 2 FeReO 6 , SrFe 2/3 Re 1/3 O 3 and their solid solutions. Sr 2 FeReO 6 and SrFe 2/3 Re 1/3 O 3 (Sr 2 Fe 4/3 Re 2/3 O 6 ) are ordered perovskites of types Sr 2 [Fe][Re]O 6 and Sr[Fe][Fe 1/3 Re 2/3 ]O 6 respectively, both of which are tetragonal at room temperature. Sr 2 FeReO 6 is metallic (ρ∼10 -3 \(\varOmega\)-cm) and ferrimagnetic below 419 K, while SrFe 2/3 Re 1/3 O 3 is semiconductive (ρ r · t · ∼10 -1 \(\varOmega\)-cm, E ρ ∼0.09 eV) and ferrimagnetic below 475 K. The SrFe 2/3 Re 1/3 O 3 compound is diffcult to saturate in the magnetization. Mossbauer spectra showed that irons in these compounds are essentially trivalent. The spectra of SrFe 2/3 Re 1/3 O 3 are composed of two lines which can be attributed to the two kinds of Fe 3+ ions located on the two sublattices. Electrical and magnetic properties of Sr 2 FeReO 6 and SrFe 2/3 Re 1/3 O 3 are discussed, taking the crystallographic structured and ionic states of ...

Carbon‐13 spin‐lattice relaxation study of linear polymers in solution

Abstract: Proton-decoupled, partially relaxed, Fourier-transform NMR of 13C in natural abundance was used to determine spin-lattice relaxation times of individual carbons of polyisobutylene, polyacrylonitrile, poly(vinyl chloride), and poly(vinyl alcohol) in solution. It is shown that the relaxation times are independent of the difference in stereochemical configuration. From the values of the nuclear Overhauser enhancement factor it is shown that the relaxation times are independent of the difference in stereochemical configuration. From the values of the nuclear Overhauser enhancement factor it is shown that the excess spin energy from equilibration of all the 13C, even of quaternary carbons, in the polymers dealt with here is transferred to the lattice mainly through 13C-1H dipolar interactions. It is shown that the segmental motions responsible for the spin-lattice relaxation of the polymer skeleton in solution can be described by the isotropic model within a good approximation, except for poly(vinyl alcohol) at low temperature. The activation energies of skeletal and internal methyl motions are estimated from the temperature dependence of the correlation time. Differences in the 13C line widths for individual carbons of polyisobutylene are discussed briefly.

Crystallization of polypeptides in the course of polymerization, III. Further studies on the growth mechanisms of poly(L‐alanine) crystals

Abstract: In order to establish the mechanism proposed previously for the formation of the extended chain crystals during the heterogeneous polymerization of the LEUCHS anhydride 4-methyl-2,5-oxazolidinedione (L-alanine NCA) in acetonitrile, oligo-L-alanines were prepared by purely organic chemical methods. Their solubility, conformations in various solvents and those in the crystallized states were studied and compared with those in the crystals formed directly in the course of the heterogeneous polymerization. It was found that the growing chain molecules became insoluble in acetonitrile and crystallized into the β-conformation when they attained a of 3. As the growing chains in the course of the heterogeneous polymerization attained of 10–13 (i.e. 7–10 from the basal plane of the original skeleton crystals) by further polymerization, they crystallized into the α-helical conformation. Due to the topochemical nature of the chain growth, this critical length for the formation of the α-helix is shorter than that found in solution for the corresponding oligomers already synthesized (i.e., > 10). It was also shown that the crystalline nuclei with the β-conformation, formed in the very early stages of the polymerization, remain throughout the polymerization. In order to examine the role of acetonitrile in this particular type of polymerization, the polymerization of L-alanine NCA was studied also in dioxane and propionitrile. The chains grown from the basal plane of the skeleton crystals with the β-conformation remain in some state like random coils until they attain the critical length for the formation of the α-helix. This critical length seems to depend on the solvation power (including the steric factor) of the solvent used. In the case of acetonitrile, the dipole-dipole interaction with polypeptides may play an important rǒle in this type of solvation. Zum Zweck der Prufung eines fruher vorgeschlagenen Mechanismus der Bildung von gestrecktkettigen Kristallen im Verlauf der heterogenen Polymerisation des LEUCHS schen Anhydrids von L-Alanin in Acetonitril wurden Oligo-L-Alanine hergestellt und deren Loslichkeit, Konformation und Kristallisationsverhalten in verschiedenen Losungsmitteln untersucht. Es zeigte sich, das die in Acetonitril wachsenden Ketten in Form der β-Modifikation auskristallisieren, sobald sie einen Polymerisationsgrad von 3 erreicht haben. Infolge der antiparallelen Anordnung der Ketten in der β-Modifikation scheint ein weiteres Wachstum der gebildeten Keime nicht moglich, so das auf der „Hauptkette” mit-Modifikation die Ketten zunachst im amorphen Zustand weiterwachsen. Sobald die wachsenden Ketten jedoch einen Polymerisationsgrad von 10–13 erreicht haben, beginnen sie in Form der α-Helix zu kristallisieren. Infolge des topochemischen Charakters der Reaktion ist diese kritische Kettenlange, die zur Ausbildung der α-Helix notig ist, geringer als fur die entsprechenden bereits synthetisierten Oligomeren in Losung. Die im Anfangsstadium der Polymerisation gebildeten Keime mit β-Modifikation bleiben im weiteren Verlauf der Polymerisation erhalten. Der Polymerisationsverlauf in den Losungsmitteln Dioxan und Propionitril wurde ebenfalls untersucht. Ein Vergleich der Ergebnisse zeigt, das der besonders gunstige Verlauf der Reaktion in Acetonitril durch eine Dipol-Dipol-Wechselwirkung zwischen Losungsmittel und Polypeptid bedingt sein konnte.

Non-polarized memory-switching characteristics of ZnTe thin films

Abstract: ZnTe thin films were prepared by the conventional vacuum-deposition method. Polycrystalline thin films could be deposited on a glass substrate at substrate temperature between 20 and 450°C. Epitaxial thin films could be obtained on GaAs and InAs single crystals at substrate temperatures higher than 200°C. Memory switching could be observed in metal-ZnTe-metal sandwich devices prepared on glass substrates. Both switching transitions, from off to on and on to off, could be performed without changing the bias polarity if a suitable value of series resistance was selected for each transition. Typical values of the series resistor were 20 KΩ for off to on and 200 Ω for on to off transitions. Transition from off to on is explained as a result of the formation of a filamentary path in the off state, followed by the formation of a metallic filament in the on state. Transition from on to off is considered a result of thermal rupture of the metallic filament.

Superresolution by Multiple Superposition of Image Holograms Having Different Carrier Frequencies

Abstract: A new technique of superresolution which makes use of a multi-exposed image hologram is described. The basic idea of this method is to use the hologram as storage medium for complex amplitude of the image of an object to be superresolved and to add up the complex amplitudes of the images of different spatial frequency ranges by multiple exposure on the hologram to synthesize the superresolved image. In this paper, a detailed analysis of the theory of this method, and the results of experiments for one-dimensional and two-dimensional objects, are presented. As a whole, the bandwidth of the optical system could be extended to the theoretically expected value.