Atomic Properties

Crystal structure

Rhombohedral

Molecular Weight

55.3 gm/mole

Heat of Formation ΔH°₂₉₈

-13.8 kcal/mol

Specific Gravity

2.54 gm/cc

Specific Heat

12.5 cal/mol°C

Lattice Energy

6.5 cal/mol°C

Lattice Constant

a_o = 5.60, c_o = 12.10

Neutron Cross Section

600 Barns

Oxidation Temperature

932°F (500°C)

Particle Shape

Blocky, Angular

Color

Black, sooty when powdered

Mechanical Properties

Knoop Hardness (100 gm load)

3200

Mohs Hardness

9.3+

Bending Strength

30....50 kg/mm^-2

Compressive Strength

200...300 kg/mm^-2

Young's Modulus

45,000 kg/mm^-2

Thermal & Electrical Properties

Melting Point

2450°C

Boiling Point

3500°C

Thermal Expansion

5 x 10^-6/°C

Thermal Conductivity 25°

.07...0.16 cal/cm-sec°C

Electrical Resistivity 25°

.01...10 ω-cm

Infrared Absorption Bands

9.5; 12.5 µ

EMF

80 µ . V ./°C

Typical Chemical Analysis

Total Boron

77.5%

Total Carbon

21.5%

Total Iron

0.2%

Total B+C

98%

ANSI/ISO Grit Sizes:

60, 70, 80, 90, 100, 120, 150, 180, 220, 240,

FEPA Grits

F4, F5, F6, F7, F8, F10, F12 F14, F18, F20, F22, F24, F30, F36, F40, F46, F54, F60, F70, F80, F90, F100, F120, F150, F180, F220, F230, F240, F280, F320, F400, F500, F600, F800, F1000, F1200

Ceramic Grades (Air classified)

-100, -200, -325, -400, -25 µ, -10 µ, -7 µ, -5 µ, -1 µ

Ceramic Group Sizes

63-50 µ, 50-40 µ, 40-28 µ, 28-20 µ, 20-14 µ, 14-10 µ, 10-7 µ, 7-5 µ, 5-3.5 µ, 3.5-2.5 µ, 60-150 mesh, 46-120 mesh