GRAPHITE TECHNOLOGY. Progress Report No. 6 for the period February 1, 1958 to April 1, 1958. Appendix: DIFFERENTIAL THERMAL ANALYSIS OF CARBONS CONTAINING PITCH AND RESIN BINDERS
A sufficient number of carefully prepared specimens of the arbitrary 'standard'' pitch-bonded coke mix have now been made and carbonized to permit selection of the optimum proportions of each and proper mixing, molding, carbonizing, and measuring methods. These were tested sufficiently to show that most of the variability in properties (density, electrical resistivity, flexural strength, dynamic modulus) arises from changes in binder rheology and from local variations in the rapidity of the coking mechanism. It is nevertheless possible to establish confidence levels, in laboratory production of small molded specimens, of approximately 99% for the green state and 95% for the carbonized state (except, of course, in flexural strength values). Highest reproducibility is attained when the mix is carefully desolvated before molding, but best properties were achieved with mixes in which some aging of the pitch had occurred. The increase in green and carbonized densities with time of aging at 125 deg C was found to be linear. The carbonizing cycle for pitchbonded structures which, without being unduly long, produces good reproducible density and strength in pitch-bonded coke specimens is one which provides relatively slow heating in the range 450 to 550 deg C. As a result of density measurements and mercury porosimetry, furfuryl alcohol monomer has been chosen as the synthetic resin to be used in later studies. Its advantages over pheaolic resins and molding powders is demonstrable in the high real density of the coke bridges formed by it, and by the low variations in coke bodies bonded with it. The completion of allowed binder studies using differential thermal analysis shows that this technique gives rapid and valid testimony regarding those properties of the binder pertinent to its role in carbon technology. Measurements of the properties of a molded commercial graphite were made, primarily to refine high- temperature measuring techniques. These indicate that macro-stresses exist in large specimens which are partially relieved by a single thermal cycle to above 2500 deg C in the specimens cut from it; the relief is attended by permanent increase in the specimen length and decrease in its room-temperature dynamic modulus and electrical resistivity. Specimens having unusual anisotropies were easily detected by unusual ratios of modulus, resistivity, and water absorption to their density. Listed in the report are the unusual relations obtained when dynamic flexural modulus was measured as a function of temperature to above 2600 deg C. These show the creep threshold'' temperature increases with continued thermal cycling to a limiting value near 2500 deg Cs the change appears to be associated with crystallite growth and reorientation. (For preceding period see NP-6622.) (auth)
- Research Organization:
- Illinois Inst. of Tech., Chicago. Armour Research Foundation
- DOE Contract Number:
- AF33(616)-5185
- NSA Number:
- NSA-12-009723
- OSTI ID:
- 4338080
- Report Number(s):
- NP-6706; Project No. G-033
- Resource Relation:
- Other Information: Project No. G-033. Orig. Receipt Date: 31-DEC-58
- Country of Publication:
- United States
- Language:
- English
Similar Records
GRAPHITE TECHNOLOGY. Progress Report No. 8 for the Period June 1 to August 1, 1958
MODIFIED-GRAPHITE TECHNOLOGY. Quarterly Report No. 1
Related Subjects
ABSORPTION- ALCOHOLS- CRYSTALS- FURFUROL- HIGH TEMPERATURE- MERCURY- PHENOLS- POROSITY- POWDERS- REFINING- STRESSES- TEMPERATURE- WATER
AGE- CARBON- CARBONIZATION- CASTING- COAL- COLOR- DENSITY- ELECTRICITY- GRAPHITE- MEASURED VALUES- MECHANICAL PROPERTIES- MIXING- PINCH- QUANTITY RATIO- RESINS- SAMPLING- SEPARATION PROCESSES- SOLVENTS- TESTING- THERMAL RADIATION