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High media roughness associated with perpendicular recording introduces the phenomenon of widely separated single needle-like corrosion growths after temperature-humidity stress. Previous generation longitudinal recording media demonstrated clusters of corrosion growths around a central media defect, which were detectable by reflected light. However, because of the isolated nature of this new type of corrosion, traditional ellipsometry is no longer effective. As a result, we have developed a method for quantifying scattered isolated corrosion growths on perpendicular recording media disk surfaces, using existing optical surface technology. Our method can detect corrosion densities down to 5000 corrosion sites/[mm.sup.2], given corrosion size at least 0.3 [micro]m in length and 7 nm in height. The amount of corrosion reveals itself as an increase in laser light scatter across a disk surface referenced to its original prestress scatter. Scanning electron microscopy and atomic force microscopy analysis of the corrosion growths verified that the scatter measurements correlate to physical properties such as density and size of corrosion needles. Index Terms--Corrosion, magnetic disk recording, optical scattering.

An investigation into the effects of sinter-forging rates on critical current density behaviour in external fields on contact resistance for Bi-2223 currents, is described.

A study reports on the development of long-length, multifilamentary Bi-2223, silver-sheathed tapes of up to 250m on a laboratory scale using the powder-in-tube approach. An optimized processing technique was used to achieve critical current density between 12,000-18,000A/cm2. Coils subsequently fabricated were stacked together to construct an experimental magnet. Experimental methodology, results and conclusions are presented.

A study investigated phase transformation and phase assemblage in Ag/Bi-2223 tapes annealed at different temperatures using a two-step sintering. One of the experimental results confirm previous research findings that a quench in between thermal cycles circumvents decomposition and recovery process of Ag/Bi-2223 process. The total heat treatment time can be reduced to 30h. Findings also suggest that by-products of phase decomposition at certain temperature ranges are adequately fine enough to function as pinning centers, although more work is required to clarify the pinning mechanism.

A high-gradient magnetic separator for paramagnetic materials has been designed. Bi-2223/Ag high-temperature superconducting tapes was used in constructing the separator because they provide the high magnetic fields required in separating paramagnetic materials. Its magnet system is made up of 12 units with a magnetic field of 3 T. The transport current density is higher than 10 raised to the fourth power A per square cm when operated at 30 degrees K.

The microstructure and J(sub c) of Ag/Bi-2223 tapes was studied under cryogenic processing conditions to determine the effect of deformation rate and silver hardness. Improved grain connectivity, alignment, Ag/core interface and critical current density resulted from cryogenic deformation. A significant increase in the hardness of silver sheath resulted during cryogenic mechanical deformation at room temperature. A 20% reduction rate of the maximum J(sub c) appeared for the tape thickness for cryogenically processed Ag/Bi-2223.

A hot-pressing technique was used to fabricate Bi-2223/Ag multifilamentary tapes to investigate its effect on grain connectivity and flux pinning. After hot pressing, the critical current density in tapes was doubled. In a 19-filament tape, Jc increased from 26,000A/cm2 to 56,000A/cm2. Improved grain connectivity, reduced secondary phases and increased core density resulted from hot-pressing as shown by microstructural analysis. In addition, the fraction of strong links improved from 47% to 68% in a 19-filament tape.

Maximum values (f2223max and I(sub Cmax)) versus sintering time were exhibited by Bi-2223 volume fraction and the critical current in Bi-2223/Ag tapes. By further heating the Bi-2223 phase decomposed and the lc decreased. An optimal processing to substantially reduce the processing time in Ag-sheathed Bi-2223 tapes was introduced based on the investigation of the effect of processing on Bi-2223 phase formation kinetics. The results showed that the Bi-2223 phase formation rate decreased after 10-15h sintering.

The effect of processing on microstructure and on Jc in PIT tapes was investigated by means of an optimized PIT processing route which is introduced and discussed from experiments. The highest Jc performance of 51,000A/cm2 had been obtained for 69-filamentary tapes at 77K and self field. The results showed that Jc is influenced on Pb distribution of Pb-2212, phase composition for the precursor powder, the core thickness and the deformation reduction rate.

The effect on Bi-2223 phase formation in other Ag alloy sheaths in PIT tapes was reported. In addition, electromagnetic, mechanical and physiochemical properties in Ag-alloy sheathed PIT tapes was studied. The results showed that in monofilamentary Ag-X alloy tapes, the reactivity of X towards oxygen influenced the formation of Bi-2223. Even small alloying additions caused a significant change in the phase kinetics of Bi-2223 and the microstructure of the oxide core. However, no significant effects in the phase formation of Bi-2223 were noted in the multifilamentary tapes.

A special non-inductive sample was made which permits the (Bi,Pb)2Sr2Ca2Cu3O(sub 10+x) Ag clad high temperature superconducting wire critical current to be unaffected by the magnetic field generated. This allows the determination of the degeneration caused by the winding procedure. The torsion test findings reveal that the torsion strain of the HTS wire during normal HTS coil winding procedure could be neglected.

A saturable magnetic core electrical fault current limiter employing a high temperature superconducting (HTS) direct current bias winding was proposed for electrical applications. The HTS winding was developed with a silver-clad (Bi,Pb)2Sr2Ca2Cu3O10+x HTS wire. The device's limiting properties were examined and its use in an electrical power transmission system was discussed.

Magnetoresistivity, alternating current susceptibility and magnetization measurements were employed for the comparative analysis of Bi-2212 single crystal, Bi-2212 tape and Bi-2223 tape. An enhanced flux pinning in the spiral grown crystals compared with those grown a layer-by-layer mechanism was observed through magnetization measurements. Results indicate that spiral growth- or mechanical deformation-induced defects function as pinning centers in Bi-based materials.

An electronic resonant circuit is proposed based on an inductor consisting of a silver-clad (Bi,Pb)2Sr2Ca2Cu3O10=x high temperature superconducting (HTS) wire. Tests were conducted using a dedicated electronic controller and a resonant circuit based on the HTS inductor was evaluated. The results show that the HTS inductor is capable of high voltage generation through a low voltage source.

A study was conducted on the influence of mechanical deformation on the critical current density and irreversibility characteristics of Bi-(Pb)-Sr-Ca-Cu-O superconducting tapes. Results reveal that hot pressing enhances critical current density in the low field region by improving grain connectivity and grain alignment. Hot deformation, however, was found to benefit only weak links.

Bulk samples of (Bi,Pb)2Sr2Ca2Cu3O10 were sintered for different times and then isothermally pressed at 850-degrees celsius under a constant pressure of 15 MPa for 1 hour. Critical temperature, mass density and critical current density were measured using EDS, XRD and scanning electron microscopy. The removal of voids in the materials under pressure and high temperature resulted in a significant increase in mass density.

A study was conducted on the influence of sintering temperature on Jc and phase composition of silver-sheathed Bi-2223 single and multifilamentary tapes. Results reveal that the Jc was more sensitive to Bi-2212 phase content in the multifilamentary tapes than in single core tapes. Sintering for 100 hours resulted in a Jc of 4.5x10(super 4) A/Cm2 for single core tapes and 3.3x10(super 4) A/cm2 for 19 core multifilament tapes.

Magnetic and transport measurements were performed on several silver-sheathed Bi-2223 tapes fabricated via the powder-in-tube method. Specifically, several tapes were heated, cooled and deformed by uniaxial pressing to investigate the inter- and intragranular mechanisms on the H-T plane that degrade critical current density. The results indicate that the critical current density obeys a power law at low fields.

The characterization of multifilamentary, silver-sheathed (Bi,Pb) 2Sr2Ca2Cu3O(10+z) (2223) tapes prepared using the powder-in-tube process was carried out. The tapes, which reach lengths of up to 46 m., were also wound into a solenoid coil with 306 turns. Prior to and after this, observations of critical current, current density, uniformity and grain growth were made. The results showed that controlling the melt process and atmosphere leads to higher critical current densities in thin 2223 tapes.

The fabrication of high-temperature superconducting coils (HTSC) for use in a fault current limiter is discussed. Specifically, a prototype fault current limiter wound from silver-sheathed (Bi,Pb)SrCaCuO-2223 wires was implemented based on the magnetic core saturable reactor principle. The prototype demonstrated low normal impedance and low energy loss 'with the HTSC dc bias,' indicating a quick return to normal operation once a fault is gone.

Transmission electron microscopy is used to analyze the effect of silver (Ag) on the superconducting properties and phase formation of Ag-clad Bi2223 superconducting tapes. The influence os Ag is studied with respect to the interface microstructure, bend strain tolerance, magnetoresistance, pinning energy and phase growth. Results indicate that the presence of Ag lowers the tapes' annealing temperature while accelerating the formation of the Bi-2223 phase. However, it also causes gain misorientations and reduces the tapes' superconductivity.

The phase formation-decomposition-recovery process for producing high-temperature superconducting Bi-2223 wires is introduced. It includes a controlled melt stage and results in silver-clad (Bi,Pb)2Sr2Ca2Cu3O(10+y) wires with a critical current density of 9 kA/cm2 at 1 T and 77 K. Such wires have a strong grain coupling due to the interfacial flux pinning, as borne out by comparisons with normal processed samples.

Magnetic hysteresis, flux creep activation energy as well as critical current densities for transport and magnetization were experimentally obtained from silver-clad Bi2Sr2Ca2Cu3Ox tapes. The high-temperature superconductors were measured at 4.0 T and 76 K under different applied fields and temperatures, respectively. They demonstrated improved critical current densities and irreversibility lines after undergoing a short-melting process.