RELATIONSHIP BETWEEN MAGNETIC PROPERTIES AND MICROSTRUCTURE OF FERRITES DURING SINTERING IN RADIATION AND RADIATION-THERMAL CONDITIONS

The studies of correlation between magnetic properties and microstructure were conducted on samples of lithium-substituted ferrite, sintered in radiation and radiation-thermal conditions. Radiation-thermal sintering was performed for compacts irradiated with a pulsed electron beam with energy of (1.5–2.0) MeV, beam current per pulse of (0.5-0.9) A, irradiation pulse duration of 500 μs, pulse repetition rate of (5–50) Hz, and compact heating rate of 1000 C/min. Sintering in thermal furnaces (T-sintering) was carried out in a preheated chamber electric furnace. The paper shows that magnetic induction does not depend on the ferrite grain size. In this case, the coercive force is inversely proportional to the grain size and depends on the intragranular porosity of ferrite samples. In contrast to thermal sintering, radiation-thermal sintering does not cause capturing of intergranular voids by growing grains and enhances coagulation of intragranular pores.

Modification of Silver Nanowire Coatings with Intense Pulsed Ion Beam for Transparent Heaters

In this report, an improvement of the electrical performance and stability of a silver nanowire (AgNW) transparent conductive coating (TCC) is presented. The TCC stability against oxidation is achieved by coating the AgNWs with a polyvinyl alcohol (PVA) layer. As a result, a UV/ozone treatment has not affected the morphology of the AgNWs network and the PVA protection layer, unlike non-passivated TCC, which showed severe degradation. The irradiation with an intense pulsed ion beam (IPIB) of 200 ns duration and a current density of 30 A/cm2 is used to increase the conductivity of the AgNWs network without degradation of the temperature-resistant PVA coating and decrease in the TCC transparency. Simulations have shown that, although the sample temperature reaches high values, the ultra-high heating and cooling rates, together with local annealing, enable the delicate thermal processing. The developed coatings and irradiation strategies are used to prepare and enhance the performance of AgNW-based transparent heaters. A single irradiation pulse increases the operating temperature of the transparent heater from 92 to 160 °C at a technologically relevant voltage of 12 V. The proposed technique shows a great promise in super-fast, low-temperature annealing of devices with temperature-sensitive components.

Low-Fluence Laser Induced Fragmentation and Desorption of 3,4,9,10-Perylenetetracarboxylic Dianhydride (PTCDA) Thin Film

Laser-induced fragmentation and desorption of fragments of PTCDA films vacuum-deposited on GaAs (100) substrate has been studied by time-of-flight (TOF) mass spectroscopy. The main effect caused by pulsed laser light irradiation (pulse duration: 10 ns, photon energy: 2.34 eV and laser fluence ranging from 0.5 to 7 mJ/cm2) is PTCDA molecular fragmentation and desorption of the fragments formed, whereas no desorption of intact PTCDA molecule was detected. Fragments formed are perylene core C20H8, its half C10H4, carbon dioxide, carbon monoxide and atomic oxygen. All desorbing fragments have essentially different kinetic energy. The mechanism of photoinduced molecular fragmentation and desorption is discussed.

Formation of periodic grain boundary in an Si thin film crystallized by a linearly polarized Nd:YAG pulse laser with an ultra sonic oscillator

ABSTRACTIn order to obtain a large silicon (Si) grain and to control the location of its boundary in a Si film melting-crystallized by a pulse laser, we have proposed to use periodic thermal distribution spontaneously induced by irradiation of a linearly polarized laser beam. We estimated the suitable amorphous Si (a-Si) thickness taking account of multiple reflection theoretically and confirmed it experimentally. Also, we proposed a novel technique to reduce the irradiation pulse number to control the grain boundary location stably in the crystallized Si film, in which the elastic wave was generated on the surface of a-Si film prior to melting-crystallization by using an ultra sonic oscillator. Owing to this technique, we can control the grain boundary location periodically with only 1 pulse irradiation in the crystallized Si film.

Studies on Ultra-short Laser Micro Structuring

A comparative study of the effect of ultrashort (0.5 ps) and short (30 ns) pulses on Laser transfer of Cr is presented in this paper. The dynamics of the process was investigated by stroboscopic schlieren imaging for time delays up to 3 νsec following the laser irradiation pulse. In contrast to the ns laser the directionality of the ejected material is very high in the case of the sub-ps laser process. The narrow angular divergence (3°) of the sub-ps pulses permits the direct dynamic transfer of the material and opens up new application possibilities for the fabrication of high spatial resolution microstructures.