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H-K9L/BK7 glass

 H-K9L(N-BK7)composition: SiO2=69.13% B2O3=10.75% BaO=3.07% Na2O=10.40% K2O=6.29% As2O3=0.36%   

 (BK7) optical glass has excellent mechanical properties and very low air bubbles and impurities, good scratch resistance. Because of its chemical stability, no special treatment grinding and polishing. Used in optoelectronics, microwave technology, and many other areas of diffractive optical elements.

H-K9L(BK7) propetyValue
opticalRefractive index1.5168
Abbe number63.96
Mechanical propetyDensity2.51g/cm3
Knoop hardness HK 100610kg/mm2
Elasticity modulus82 x 103kN/mm2
Poisson ratio μ0.21
Thermal propety Softening ponit719°C 
Annealing point657°C 
Strain point624°C 
Thermal conductivity1.1W/m.°C 
Specific heat879J/kg.°C 
Thermal expansivity7.1×10E-6/K
Chemical propetyHydrolysis2Class
Acidproof1Class
Alkalineproof2Class