Hexagonal boron nitride powder having specific bulk density and residual Fe particles, and method for producing same
A hexagonal boron nitride (h-BN) powder is disclosed in which primary particles of the powder exhibit a ratio (D/d) of long diameter (D) to thickness (d) in a range of 5 to 10. Agglomerated particle bodies made of the primary particles have an average particle diameter (D 50 ) in a range of 2 μm to 200 μm, inclusive, and the powder has a bulk density in a range of 0.5 g/cm 3 to 1.0 g/cm 3 . In an exemplary method for producing the h-BN, boron carbide is nitridizated in a nitrogen partial pressure of at least 5 kPa at 1800° C. to 2200° C., inclusive. B 2 O 3 (or precursor thereof) is added to the nitridization product to produce a mixture. The mixture is decarbonized in a non-oxidizing atmosphere at a 1500° C. to 2200° C., inclusive. The decarbonization product is pulverized and subject to particle-size classification, yielding H-BN powder. The method includes a depressurizing step, performed at 100 kPa or less either during nitridization or after decarbonization.
1. A hexagonal boron nitride powder, characterized in that:
primary particles of the powder exhibit a ratio (D/d) of long diameter (D) to thickness (d) in a range of 5 to 10;
agglomerated particle bodies made of the primary particles have an average particle diameter (D 50 ) in a range of 2 μm to 200 μm, inclusive; and
the powder has a bulk density in a range of 0.5 g/cm 3 to 1.0 g/cm 3 and impurity Fe at a concentration not greater than 500 ppm, the impurity Fe being as spherical particles having respective diameters not greater than 50 μm.
2. The hexagonal boron nitride powder of claim 1 , wherein the average particle diameter (D 50 ) and void ratio of the agglomerated particle body are in a range of 20 μm to 80 μm, inclusive, and not greater than 50%, respectively.
3. The hexagonal boron nitride powder of claim 2 , having a powder strength of at least 0.4, wherein:
powder strength is represented by a ratio of one average particle diameter to another average particle diameter of the agglomerated particle body;
the one average particle diameter is obtained by injecting hexagonal boron nitride powder at a pressure of 0.3 MPa in a dry condition and measuring particle diameters of the agglomerated particle bodies; and
the another average particle diameter is obtained by injecting hexagonal boron nitride powder at a pressure of 0.01 MPa in a dry condition and measuring particle diameters of the agglomerated particle bodies.
4. The hexagonal boron nitride powder of claim 2 , wherein the agglomerated particle body is produced by baking.
5. The hexagonal boron nitride powder of claim 4 , having a powder strength of at least 0.4, wherein:
powder strength is represented by a ratio of one average particle diameter to another average particle diameter of the agglomerated particle body;
the one average particle diameter is obtained by injecting hexagonal boron nitride powder at a pressure of 0.3 MPa in a dry condition and measuring particle diameters of the agglomerated particle bodies; and
the another average particle diameter is obtained by injecting hexagonal boron nitride powder at a pressure of 0.01 MPa in a dry condition and measuring particle diameters of the agglomerated particle bodies.
6. The hexagonal boron nitride powder of claim 1 , wherein the agglomerated particle body is produced by baking.
7. The hexagonal boron nitride powder of claim 6 , having a powder strength of at least 0.4, wherein:
powder strength is represented by a ratio of one average particle diameter to another average particle diameter of the agglomerated particle body;
the one average particle diameter is obtained by injecting hexagonal boron nitride powder at a pressure of 0.3 MPa in a dry condition and measuring particle diameters of the agglomerated particle bodies; and
the another average particle diameter is obtained by injecting hexagonal boron nitride powder at a pressure of 0.01 MPa in a dry condition and measuring particle diameters of the agglomerated particle bodies.
8. The hexagonal boron nitride powder of claim 1 , produced by a method comprising the steps of:
nitridizing boron carbide in a nitrogen atmosphere having a nitrogen partial pressure of at least 5 kPa and a temperature of 1800° C. to 2200° C., thereby forming a nitridization product;
to the nitridization product, adding B 2 O 3 and/or a precursor thereof, thereby forming a mixture;
decarbonizing the mixture in a non-oxidizing atmosphere at a temperature of 1500° C. to 2200° C., thereby forming a decarbonization product; and
pulverizing and classifying the decarbonization product according to particle size, thereby producing hexagonal boron nitride powder;
wherein, during nitridization or after decarbonization, depressurization is performed at a pressure less than 100 kPa.