John Tanaka

Ternary hydrides of calcium and strontium with iridium, rhodium and ruthenium

Abstract The ternary hydrides, Ca 2 IrH 5 , Sr 2 IrH 5 , Ca 2 RhH 5 , Sr 2 RhH 5 , Ca 2 RuH 6 , and Sr 2 RuH 6 have been prepared. In each case the alkaline earth hydride was reacted with a Group VIII metal at high temperatures under a hydrogen atmosphere. X-Ray powder data showed that the two metal atoms are arranged in the fluorite structure. Powder neutron diffraction showed that the hydrogens octahedrally coordinate the Group VIII metal atom. Random vacancies of hydrogen sites were indicated for the iridium compound. The elemental analyses and magnetic susceptibility data support the structural assignments.

Space charge in polyethylene/ionomer blends

Measurements of thermally stimulated currents were made on ionomer/polyethylene blends. The objective of this work was to study space charge formation in these materials. Two ionomers were compared; both ionomers contained methacrylic acid, neutralized by zinc in one and by sodium in the other. A large current peak centered near 60/spl deg/C was observed in all blends and associated with the motion of space charges injected into the blends during poling. All blends accumulated large negative space charge concentrations. The approach to the equilibrium space charge distribution (negative and spatially uniform in all blends) is much more rapid in the blends containing the sodium ionomer than in the blends containing the zinc ionomer. >

A Study of the Gaseous Degradation Products of Corona-Exposed Polyethylene

The gaseous degradation products of low density polyethylene exposed to corona discharges were investigated. Temperature and applied voltage were varied independently in order to determine the effect of each on the chemical processes involved in the degradation. Based upon statistical analysis of the results, temperature was found to have an anomalous effect on the accumulation of organic gas products in that increased temperature resulted in lesser amounts of these gases being found.

What is TSC

The technical background for the thermally stimulated current (TSC) technique is presented. The effect of metal polymer contacts on the TSC method is discussed. The transitions in amorphous polymers are described. The dynamic properties of polyethylene using TSC method are given.<<ETX>>

Degradation Product Analysis for Polymeric Dielectric Materials Exposed to Partial Discharges

Partial discharge phenomena appear to play an important role in insulation failure, and thus the analysis of products resulting from such degradation may lead to an understanding of insulation breakdown mechanisms and more accurate determination of insulation lifetimes. Progress in the area of degradation product analysis is reviewed for solid and liquid insulating materials.

Ternary hydrides of calcium and strontium with palladium

Abstract New ternary hydrides of the stoichiometry SrPd 2 H, Sr 2 PdH 4 , and Ca 3 Pd 2 H 4 have been prepared. These compounds were formed by reacting the respective alkaline earth binary hydride with palladium under approximately 625 mm of hydrogen pressure at temperatures ranging from 750 to 850° for 8–10 hr. Differential thermal analyses were used as a guide in evaluating optimum reaction temperatures and decomposition behavior of the reactants and products. The SrPd 2 H was also formed by intermetallic hydrogenation. X-Ray diffraction data for each ternary were indexed as cubic. Electrical resistance measurements for each of the ternary hydrides indicated metallic behavior. Magnetic data showed that the ternary systems were diamagnetic or weakly paramagnetic.

Space charge induced in stressed polyethylene

Measurements of space charges induced by poling have been made on XLPE (cross-linked polyethylene) samples cut from AC cables aged under different conditions. The approximately 220- mu m-thick samples were obtained by peeling. Gold electrodes were evaporated on the samples, the samples were poled at approximately 0.12 MV/cm (2.75 kV per sample) for three hours at 70 degrees C, and the space charge was determined by the thermal pulse technique. The amount of space charge induced in different samples by identical poling conditions was larger in the samples with the longer exposure to AC stress. The total amount of space charge which could be induced by poling was also found to correlate with other parameters, such as AC breakdown strength. In addition, the space charge dissipation rate was monitored for several weeks after poling. Samples aged at room temperature with both electrodes grounded retained more than half their original space charge after one week. It is noted that it is highly probable that the determination of space charges will be a powerful method for estimating the degree of degradation of aged cables.<<ETX>>

Analysis of cables with visible halos

Halos found in polyethylene cables removed for failure analyses are characterized. The halos are produced by some volatile materials. Water analysis shows a higher water content within the halo than in areas where the halo does not exist. Some organic volatiles introduced at the time of manufacture remain. Acetophenone is variable depending on the particular failure sample. Other organics, some dicumylperoxide decomposition products and some not, are also identified. None of these could be specifically correlated with the presence or absence of the halo. The character of the halos was found to change slowly with time after the cable was removed from the ground. The questions raised by these findings are discussed.

Chemical Changes Created by High Energy Ions in Polyethylene

Argon and oxygen ions were accelerated with energies of 50 to 150 keV and rastered across high density polyethylene. The free radicals formed in the ion-implanted polyethylene were studied using an electron spin resonance spectrometer. The free radicals formed were stable in air and even survived solvent separation of the undamaged polymer from the ion damaged polymer. Chemical characterizations indicated that pregraphitic or graphitic-like particles are formed with defect sites which are, in effect, free radicals stabilized by a polyaromatic system.

Effect of DC tests on induced space charge

Poling-induced space charges in peeled samples of AC-aged, DC-tested cables were studied using the thermal pulse technique. Samples were poled at approximately 0.12 MV/cm for 3.5 h at 70 degrees C using the same polarity as that used for the DC tests. Previous work seemed to indicate that DC testing could have permanent effects which could be detected by the amount of poling-induced charge. An attempt was made to examine this by using three samples with about the same length of AC aging but with different amounts of DC testing. The sample with one DC test and the sample with 23 DC tests were appreciably oxidized, whereas the sample with 11 DC tests was not oxidized. In addition, when the sample was pulsed from the face exposed to the positive poling electrode, a negative space charge was observed. When it was pulsed from the opposite face, a positive space charge was observed. The space charge decay was found to be asymmetric. AT 70 degrees C, the negative space charge decays faster than the positive space charge. At 60 degrees C, the decay was observed to be about the same on both sides. When the poling field is small, both sides have a positive space charge. For larger poling fields, the space charge in the film close to the positive electrode is negative.<<ETX>>