Jan Ziaja

Plasma metallization textiles as shields for electromagnetic fields

The aim of this paper is electromagnetic testing of innovative shielding textiles in the frequency range from 30 MHz up to 1300 MHz. These new materials were obtained using plasma metallization process. The metallic film was deposited by magnetron sputtering in argon atmosphere from Zn-target on the polypropylene (PP) nonwovens. The microstructure of Zn-films was studied by scanning microscopy (SEM). Obtained metallic layers were characterized by good adhesion to PP and shielding effectiveness (SE) over 50 dB. It was indicated that 3D structure of the textile surface influences the value of SE.

Preparation and Properties of Polymer Composites Filled with Low Melting Metal Alloys

Composites of polymers and low melting point metal alloys are little known classes of materials. In this work thermoplastic composites filled with differing contents of Woods metal or Cerromatrix alloys have been studied in respect to their microstructure, mechanical, thermal, and electrical properties. It was found that the type of filler employed had significant influence only on the mechanical and thermal properties of composites. The results of volume resistivity show that all composites conduct electrical current well, even when metal loading is below 10vol.%. Low percolation threshold is caused by a unique interpenetrating network structure created by polymer and metal co-continuous phases.

Metallic and oxide Zn and Ti layers on unwoven fabric as shields for electromagnetic fields

The paper presents results of measurement of electromagnetic wave shielding effectiveness by shields based on polypropylene unwoven (PP) with metallic, or oxide layer. Thin films on PP fabric were made by means of pulsed magnetron sputtering. Deposited materials were Zn and Ti, fitted on magnetron gun of the WMK-100 Type in argon and oxygen background. Manufactured shields were characterised by good adhesion and shielding effectiveness (SE) over 35 dB in frequencies range from 10 MHz to 1.3 GHz.

Composites Made of Polypropylene Nonwoven Fabric with Plasmas Layers

Engineering of materials used for shielding from electromagnetic fields is currently one of the most extensively developing field of applications of composite materials (Bula et al., 2006; Jaroszewski & Ziaja, 2010; Koprowska et al., 2004, 2008; Sarto et al. 2003, 2005; Wei et al., 2006; Ziaja et al., 2008, 2009, 2010). The choice of suitable materials for the shields and their appropriate arrangement have an essential meaning. Development of lightweight and resistant to environmental exposure shielding materials is possible by using substrates of polypropylene and plasma technology (Ziaja&Jaroszewski, 2011).

Investigations of the field emission current from bismuth ceramic cathodes

In this work the investigations of the emission current from Bi/sub 2/Sr/sub 2/Ba/sub 2/Cu/sub 3/O/sub x/ and Bi/sub 2/Sr/sub 2/BaCu/sub 2/O/sub x/ ceramic cathodes are presented. Experiments were carried out in the vacuum chamber at pressure within the range of 10/sup -8/ Tr (10/sup -6/ Pa), with DC high-voltage power supply and high-class digital electrometer. Current-voltage and Fowler-Nordhelm characteristics for the superconducting cathodes at liquid nitrogen temperature were obtained for various distances between electrodes. Current vs. temperature characteristics were also measured. For some measurements the transparent anode technique was employed in order to provide information about emission origin point. Emission current was registered for the electron emission originating from a single emission center. Superconducting state did not influence current-voltage dependences. It was observed for superconducting cathodes that emission current abruptly changes in the vicinity of the superconducting transition temperature T/sub c/. Emission current was stable and practically constant for the temperatures below T/sub c/ and became unstable and noisy for the temperatures above T/sub c/. Emission current rate depends on the temperature range of the superconducting transition /spl Delta/T/sub c/. Superconducting parameters of the cathodes: critical temperature T/sub c/, temperature range of the superconducting transition /spl Delta/T/sub c/ and critical current density j/sub c/ were also measured. It was found that sorbtion phenomena on the surface of cathodes during cooling and heating influence emission current values and play a major role in the emission phenomena.

Application of magnetron-sputtering-obtained Ce-Zr-O2-x-oxide thin layers to gas detection

Thin layers of Ce-Zr-O2-x with varied chemical and phase composition were deposited by magnetron sputtering with pulse power supply system. The phase transition in the function of temperature and additionally during hydrogen treatment were studied. The variation of resistivity of such layers was found during changing of the gas atmosphere. By comparison, the properties of thin films prepared by sol-gel method were also studied.

Field emission current from high-T/sub c/ ceramic cathodes

In this work, the results of the emission phenomena investigations are presented. Experiments were conducted for high-T/sub c/ superconducting ceramic materials YBaCuO and BiPbSrCaCuB compositions. The Fowler-Nordheim characteristics and the current-temperature dependences were observed for superconducting and nonsuperconducting cathodes. It was noticed that the emission current value abruptly changes in the vicinity of the critical temperature. All measurements were done in the vacuum chamber under a pressure of 10/sup -6/ Pa. X-ray diffraction analyses and scanning electron microscopy (SEM) examinations of ceramic electrodes were also performed.