Harris A. Goldberg

Graphite fibers and filaments

Contents: Introductory Material on Graphite Fibers and Filaments.- Synthesis of Graphite Fibers and Filaments.- Structure.- Lattice Properties.- Thermal Properties.- Mechanical Properties.- Electronic Structure.- Electronic and Magnetic Properties.- High Temperature Properties.- Intercalation of Graphite Fibers and Filaments.- Ion Implantation of Graphite Fibers and Filaments.- Applications of Graphite Fibers and Filaments.- References.- Subject Index.

Synthesis of Graphite Fibers and Filaments

This chapter considers the methods by which the various types of fibers are produced. It is noted that ex-polymer fibers are produced by methods which lie in the area of applied polymer chemistry. Several reviews of their manufacture have been written. Therefore, only a brief description of their preparation is given here, enabling the reader to relate structural features to growth methods. The methods of growing CCVD filaments is considered in greater detail. The growth of the CCVD filaments in lengths of hundreds of millimeters has not been reviewed previously. It is emphasized that commercial carbon fibers are manufactured from polymers, and that one type (ex-PAN) dominates the commercial market, though low cost isotropic pitch fibers are also beginning to find wide application in high bulk, low performance applications. The present review of fiber growth would therefore seem to be out-of-balance with respect to current commercial utilization. However, the most interesting physical experiments have been carried out on the newer CCVD fibers, thereby providing the rationale for the balance we have chosen.

Synthesis And Properties of Multifunctional Polymers

Abstract : Recent work aimed at developing new polymers which exhibit useful optical, electro-optical, and piezoelectric properties is presented. The materials under study are polymers with methacrylate backbones and oxynitrostilbene side chains. The synthesis is outlined, and pyroelectric, electro-optic, and thermal property data are reported and discussed.

Naphthalocyanine chromophores for WORM-type optical data storage media

Hoechst Celaneses proprietary naphthalocyanine record-ing layer materials exhibit excellent performance for a write-once read many (WORM) optical data storage media. This pit-forming medium shows a CNR greater than 50 dB and a bit error rate less than 1 x 10 for data recorded at either 780 or 830 nm. The stability under accelerated aging conditions is superior to that for coririercial media.

Applicability of the microwave cavity perturbation method for conductivity measurements on carbon fibers

A microwave cavity perturbation technique has been used to measure the resistance per unit length of carbon fibers. These materials and other test materials used in these measurements such as copper, evenohm, and tungsten, have much higher conductivities than polymeric materials which have been investigated previously with this technique. The 1500–5000‐Ω resistance of the carbon fibers lay in the region near the limit of applicability of the perturbation technique, thereby affording a means of investigating this limit. The condition Rs/Zc>2 where Rs is the sample resistance and Zc is the characteristic impedance of the cavity, appears to be a useful condition for estimating the limit of applicability.

Ion Implantation of Graphite Fibers and Filaments

Ion implantation is an important technique for modifying material properties through the introduction of impurity atoms or the creation of lattice defects in a controlled way. The technique is important in the semiconductor industry for making p-n junctions by, for example, implanting n-type impurities into p-type host materials. From a materials science point of view, ion implantation allows essentially any element of the periodic table to be introduced into the near-surface region of essentially any host material, with quantitative control over the depth and composition profile of the impurity by proper choice of ion energy and fluence (i.e., the total number of implanted ions per unit area of sample). Furthermore an important application of ion implantation is in the synthesis of metastable alloys which could not be produced by other means.

Dynamic Laser Marking Experiments On An Organic Optical Storage Medium

Dynamic GaAlAs diode laser marking experiments on an optical data storage medium are reported. The medium comprises thin films of a proprietary organic recording layer that are spin coated onto both glass and plastic disk substrates. These amorphous films with high substrate incident reflectivities (R - 30%) are stable to both air and moisture. Writing experiments were performed in the substrate incident mode. Readable marks were made with 2 to 15mW of laser power at pulse widths down to 50 ns. The marks are pits with well-defined rims. The dependence of laser recording quality on both disk and marking parameters will be discussed.

Electro-optic and nonlinear optical polymers and devices

Early work at Hoechst Celanese1 demonstrated that methacrylate polymers with mesogenic side chains could be made with reasonably large electro-optic activity. The mesogenic side chains are polar so that a non-centrosymmetric structure can be obtained by heating a film near its Tg in a strong d.c. electric field and thus orienting the side chains. In Figure 1, the general structure of methacrylate based electro-optic polymers using polar nitro-stilbene chromophores is shown.

Accelerated Aging Studies for Organic Optical Data Storage Media

The excellent stability of Hoechst Celanese WORM media was demonstrated in accelerated aging studies. CNR data was measured as a function of exposure time for disks exposed to 65°/80% RH, 80°/80% RH, and 90°/80% RH. Disks were also exposed to a high intensity xenon lamp to compare the relative stability to visible and ultraviolet radiation. The stability of the polycarbonate substrate and the recording layer were investigated.

STM Analysis of Pit Formation In Organic Worm Media

Pits made in organic WORM media have been examined using an STM. The relationships of STM observations to media performance and properties are discussed.