HPBN development

Introductory remarks on the physical and mechanical properties of hot-pressed boron nitride (HPBN) were given first. Types of HPBN include HD 0092 (HBC), TS1251, and modified HPBN (SS3500, SS3900). The object of the work was to improve properties affecting thermal stresses and not affect dielectric and ablation characteristics. Experimental procedures were listed. Figures and tables showed the following for TS1251 and SS3500: ultrasonic modulus of HPBN vs temperature, average ultimate tensile strength vs temperature (perpendicular and parallel to pressing), stress--strain comparisons, comparisons of compressive strength vs temperature (perpendicular and parallel to pressing), thermal expansion of HPBN (parallel and perpendicular to pressing), thermal conductivity of HPBN, average dielectric properties of HPBN, ablation test data for HPBN, material models for HPBN, typical flight thermal stress comparison. It was concluded that materials with limited metallic inclusions are preferred, modifying present HPBN improves properties considerably without affecting ablation and dielectric properties, thermal stress factors for SS3500 are considerably improved over TS1251, and thermal stress analyses indicate that the SS3900 HPBN could improve the thermal stress ratio over SS3500. This report appears to be a set of slides or similar material for a talk, and contains no text as such