Accession Number : AD0674633

Title :   PREPARATION AND CHARACTERIZATION OF HIGH QUALITY SINGLE CRYSTAL REFRACTORY METAL CARBIDES.

Descriptive Note : Technical rept. Apr 67-Apr 68,

Corporate Author : WESTINGHOUSE ELECTRIC CORP PITTSBURGH PA ASTRONUCLEAR LAB

Personal Author(s) : Tobin,J. M. ; Fleischer,L. R.

Report Date : MAY 1968

Pagination or Media Count : 64

Abstract : A new and generally more applicable technique for growing large single crystals of transition element carbides was developed. Crystals of a nominal 0.25-inch diameter and 1.0-inch length were obtained in yields of over fifty per cent for HfC, ZrC, TaC and alpha-Ta2C. In the previously reported technique, the crystals of ZrC were grown during the process of direct reaction of the elements using a multiple-step increased temperature heating cycle. That technique was not readily adapted to the high yield preparation of crystals of the other three carbides. The new technique starts with the preparation of fully dense carbide rod and homogenized at the highest carbon content attainable for the carbide. The rods are given a critical strain in axial compression at very high temperatures. Subsequent annealing at a higher recrystallization temperature causes the growth of very large grains. The growth of the grains to full rod diameter and length occurs during isothermal annealing by means of solid state grain boundary movements under the influence of the strain energy absorbed by the carbides. Such grains have been shown to be single crystals of a high degree of crystalline perfection, free of strain and homogeneous. (Author)

Descriptors :   (*CARBIDES, *SINGLE CRYSTALS), (*CRYSTAL GROWTH, CARBIDES), HAFNIUM COMPOUNDS, TANTALUM COMPOUNDS, ZIRCONIUM COMPOUNDS, RODS, STRAIN(MECHANICS), ANNEALING, GRAIN SIZE, RECRYSTALLIZATION

Subject Categories : Ceramics, Refractories and Glass
      Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE