Methods of thermal conductivity measurement of high polymers are reviewed critically and a method devised by one of the authors is described somewhat in detail. Necessity of material standards for the measurement is also asserted. The investigations of the thermal conductivities of amorphous polymers including space network polymers and of semi-crystalline polymers in the temperature range from room temperature to their softening or melting point are summarized. The temperature dependence and some relationships, such as the change of temperature dependence of the conductivity around glass transition vs. glass transition temperature, the conductivity vs. crosslinking density, are described.
Tunable four-photon parametric fluorescence, which is valuable for investigating material nonlinearities and parametric devices, was studied theoretically and experimentally. Theoretical analysis leads to the conclusion that the emitted power depends directly on the focusing of the pumping beam, unlike the process of the three-photon parametric fluorescence which is independent of this beam focusing. The calculation of the phase-matching conditions for nonlinear crystals such as KDP, ADP, TiO2 and CdS shows that collinear phase-matching can be realized over the visible region using a ruby laser for pumping. Tunable emission was observed experimentally in the visible range from 4200 Å to 5300 Å with KDP, ADP and TiO2 crystals pumped by a Q-switched ruby laser. The magnitude of the third-order nonlinearities for these crystals were also evaluated experimentally, and compared with previous data derived by the three-wave mixing and the third harmonic generation methods.
Fabrication technologies and electrical performance of n type Germanium oscillators, 200 to 500 microns long and with carrier concentration of 1015cm-3 at 77°K are reported here. The n+-n-n+ structure was prepared by means of epitaxial solution regrowth. The observed waveform when the DC field is applied along the <100> direction is in good agreement with the result of one-dimensional computer simulation of accumulation mode operation. When the field was along <511>, <311>, <211>, <111>, <122> or <110>, no current oscillation was observed.
A new far infrared spectroscopic method using an InSb tunable detector-tuned by a magnetic field-is proposed. If a far infrared source, obeying the Rayleigh-Jeans relation, is used with a grating spectrometer, whose transmittance is independent of wavelength, the detector output produced by the spectrum of order m is proportional to m3 for a thermal detector, to m for an InSb non-tunable detector while it has a sharp peak at some fixed m for a tunable detector. This advantage of the tunable detector is illustrated by the measurement of absorption spectra of water vapor using various values of the magnetic field. It is proposed to change the spectral region covered by the detector synchronously with the motion of the grating, thus eliminating low-frequency-pass filters.
Equilibrium diagram and glass transition temperature in the system Te-GeTe-GeSe2 were obtained by differential thermal analysis. Temperature dependence of electrical conductivity and thermoelectric power on a few samples were obtained, and possibility of ionic conduction was discussed. Potential difference across a sample in memory state and memory waiting time were obtained as a function of current on a large number of samples. It became evident that there are two types of crystallization in memory phenomenon. One of them is caused only by Joule's heat and the other arises not only from Joule's heat but also other phenomena which are due to current. As one of these phenomena the effect of Peltier cooling was discussed.
Titania whiskers 7 were grown by a vapour phase reaction from a mixture of TiCl4 and SiCl4 of various concentration. The concentration range of SiCl4 under which the whiskers .grow was about 0.015 υ/o-0.8 υ/o. The temperature range for the growth was about 450°C_??_700°C. Growth rate, feature of aggregation etc. of the whiskers varied with the concentration of SiCl4. For instances, the growth rate at 620°C was about 3 μ/h at the concentration of 0.015 υ/o, 250 μ/h at 0.28 υ/o and 2 μ/h at 0.8 υ/o. Silica deposited from the vapour was guessed to be of amorphous phase.