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Recently, the study on the application of atmospheric plasma treatment has gradually increased because it requires high cost vacuum systems, and the flexibility of application to a continuous process. This paper reports on the new application of medium frequency atmospheric plasma to the continuous surface cleaning of aluminum wire for magnet wire manufacturing. Magnet wire is widely used for transformers and motors. It is composed of a metallic conductor of copper or aluminum, and various types of enamel coated layers as insulator. Copper has been mainly used as a conductor of magnet wire. The use of aluminum conductor has gradually increased, replacing the copper and thus, reducing the wire weight. In order to be used as a conductor of magnet wire, the copper or aluminum wire should be drawn to a proper size. After that, the drawn wire is coated with enamel varnish, and is finally annealed at a temperature of approximately 400°C. In this process, in order to obtain enough bonding strength between conductor and enamel, the drawn wire should have a clean surface without lubrication oil residuals from the wire drawing process. As the lubrication oil for aluminum wire drawing is highly viscous and insoluble in water, tri-chloroethane (1,1,1-TCE), one of the most powerful cleaning agents has been most widely used. However, the manufacture and use of 1,1,1-TCE is restricted by law due to its environmental impact on the ozone layer. This study was performed to solve the environmental problems of conventional chemical cleaning agents such as 1,1,1-TCE by applying a medium frequency atmospheric plasma treatment. Medium frequency and high voltage power supplier (20 kHz, 7∼1.5 kV) was used as a plasma power source, and a tube type electrode was prepared for continuous wire cleaning process. For the evaluation of cleaning effect, not only naked eye inspection, but also surface tension test and peel strength tests were performed. The results were quite good. The wire, which was exposed to corona discharge in the tubular electrode for 0.3–1.2 s, had better surface cleanness than that of wires treated with 1,1,1-TCE. This cleaning effect comes from the reactive oxygen ions generated in the plasma.

A new family of superconducting cuprate oxides based on mercury and thallium, Hg 1− x Tl x Ba 2 ( Ca 0.86 Sr 0.14 ) 2 Cu 3 O 8+ δ (x=0.25, 0.50, 0.75; denoted as Hg, Tl-1223), have been synthesized. All the diffraction lines of the samples were well indexed on the tetragonal “1223” (space group: P4/mmm) structure. X-ray powder diffraction data and EPMA results suggest that the compounds form complete ranges of solid solution. The superconducting transition temperatures for the as-synthesized samples are at about 124 to 128 K. After annealing in an argon atmosphere at 400°C for 6 h, the T c 's of the samples with x =0.25 and 0.50 have been found to increase to 132 K. The Tl substituted compounds are quite stable up to 550°C whereas pristine HgBa 2 (Ca 0.86 Sr 0.14 ) 2 Cu 3 O 8+δ starts to decompose below 300°C. The intra-grain critical current density of Hg, Tl-1223 largely enhances as the thallium content increases. The Tl in Hg, Tl-1223 plays significant roles not only to stabilize the Hg-1223 phase but also to enhance the pinning properties.

A new mercury-based superconductor Hg[sub 0.5]Tl[sub 0.5]Ba[sub 2](Ca[sub 1[minus]x]Sr[sub x])[sub 2]Cu[sub 3]O[sub 8+[delta]] (x = 0.14, denoted as Hg,Tl-1223) was prepared by solid state reaction of HgO, Tl[sub 2]O[sub 3], Ba[sub 2]CuO[sub 3+x], and Ca[sub 1[minus]x]Sr[sub x]CuO[sub 2]. X-ray powder diffraction analysis revealed that the Hg,Tl-1223 is isostructural with pristine HgBa[sub 2](Ca[sub 1[minus]x]Sr[sub x])[sub 2]Cu[sub 3]O[sub 8+[delta]]. The crystal symmetry is tetragonal with a space group of P4/mmm, and lattice parameters of a = 3.8649(1) [angstrom] and c = 15.9573(2) [angstrom]. The [Tc] for the as-synthesized sample is about 128 K. After annealing the sample in an argon atmosphere at 400 C for 6 h, the [Tc] has been found to increase to 132 K. In contrast to other mercury-based superconductors, HgBa[sub 2]Ca[sub n[minus]1]Cu[sub n]O[sub 2n+2+[delta]] (n = 1, 2, 3), the Hg,Tl-1223 compound is quite stable even at 500 C in oxygen and argon atmospheres. The Tl substitution at the Hg site appears to stabilize the Hg,Tl-1223 phase and enhance pinning. The critical current density of the Hg,Tl-1223 obtained from the magnetic hysteresis loops is approximately twice larger than that of pristine HgBa[sub 2](Ca[sub 1[minus]x]Sr[sub x])[sub 2]Cu[sub 3]O[sub 8+[delta]].

A new mercury-based superconductor Hg 0.5 Tl 0.5 Ba 2 Ca 1- x Sr x Cu 2 O 6+ δ ( x = 0.14, denoted as Hg, Tl-1212) was synthesized from the reaction of HgO, Tl 2 O 3 , Ba 2 CuO 3+ x , and Ca 1- x Sr x CuO 2 . X-ray powder diffraction analysis showed that the thallium completely substitutes for the mercury sites in the rock-salt [HgO δ ] layer. The as-synthesized Hg, Tl-1212 has a T c of 122 K. Surprisingly the T c decreased to about 100 K upon annealing in an oxygen atmosphere at 350°C for 8 h while the argon annealing did not show any substantial change in T c under the same condition. The crystal symmetry was found to be tetragonal (P4/mmm) with lattice parameters a = 3.8496 (1) A and c = 12.6536 (4) A . The Hg, Tl-1212 is quite stable up to 450°C. The intra-critical current density of Hg, Tl-1212 is about twice larger than that of HgBa 2 Ca 1- x Sr x Cu 2 O 6+ δ ( x = 0.14). The substitution of Tl for Hg clearly stabilized the Hg, Tl-1212 phase as well as enhanced the pinning property.

A single-phasic polycrystalline sample of superconductor Bi 1.8 Pb 0.4- Sr 2 Ca 2 Cu 3 O y ( T c = 108 K) was obtained by reaction of prereacted Bi 1.8 Pb 0.2 Sr 2 Ca 2 Cu 3 O y with PbO under low oxygen pressure, which was fully characterized by X-ray diffraction and measurements of electrical resistivity and magnetic susceptibility. 17 O NMR measurements have been performed for the compound at 300 K. Spectrum of the Bi 1.8 Pb 0.4 Sr 2 Cu 3 O y compound contained two distinctive peaks in the paramagnetic region, in which a broad resonance at 2150 ppm and a relatively sharp peak at 1600 ppm were assigned as the oxygens of two outer CuO 2 planes and a central CuO 2 layer, respectively. In the diamagnetic region a series of peaks were observed about 350 ppm, which are more likely to be associated with the oxygen resonance of the SrO plane. The BiO resonance expected from the BiO plane appears to be smeared out, which might be attributed to the incommensurate modulation and nonperiodic oxygen position of the Bi 2 O 2 layers.

The corrosion behavior of a TiAlN coated surface in a hydrofluoric gas atmosphere was investigated for its application to the Teflon extrusion process. Teflon is a high temperature thermo-plastic that fills the need for molded parts, electrical insulation or extrusions requiring chemical resistance and good dielectric properties. Its properties are well suited for mechanical, electrical and chemical components and cable insulation. However, Teflon in the molten state is highly corrosive to most metals because of the hydrofluoric (HF) gas generated by decomposition of molten Teflon. Therefore, special corrosion resistant alloys must be used for parts of the equipment which come in contact with molten Teflon. Although a few super-alloys like ‘Hastelloy C-276’ or ‘Monel 400’ are suitable for Teflon processing, these materials have some problems, such as high cost, and poor formability, hardness and mechanical strength. We investigated coating TiAlN onto an extrusion die and nipple for Teflon cable insulation, and the material of the die and nipple was changed from Hastelloy C-276 to alloy steel. TiAlN coating has one of the highest working temperatures (800°C) due to the surface being covered with a stable and passive aluminum oxide layer. When TiAlN is exposed to a HF gas atmosphere in working conditions, it reacts with HF and forms aluminum fluoride (AlF 3 ), which is chemically very stable to various corrosives such as acid, alkaline, alcohol and even HF. The process was quite successful and we applied the new die and nipple made of alloy steel with TiAlN coating to Teflon cable extrusion. No corrosion occurred, and we achieved a higher quality surface of the extruded cable and a much longer life for the die and nipple. The TiAlN coated surface of the die and nipple after Teflon extrusion was investigated by SEM, ESCA and AES in order to confirm the formation of AlF 3 .