Silicon Nitride Powder Composition to Suppress Blackness
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Solution Overview
Problem
Silicon nitride powders can appear tinged with blackness due to variations in raw materials and production conditions, potentially affecting the properties and appearance of sintered compacts, with the specific causes unclear.
Innovation Solution
A silicon nitride powder formulation with controlled ratios of non-nitride silicon, oxygen, carbon, and iron, along with adjusted firing and milling processes, to achieve a white appearance and suppressed blackness, ensuring consistent properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional silicon nitride powder production methods are used, then production cost and process simplicity are maintained, but the powder appearance becomes inconsistent with blackness appearing in some production lots
Solution Approach 1:
The invention changes the chemical composition parameters of the silicon nitride powder by strictly controlling the ratios of non-nitride silicon to oxygen (R Si /R O ≤ 0.19) and non-nitride silicon to oxygen to carbon ((R Si ×R C )/R O ≤ 2×10 -4). This parameter control ensures white appearance and suppresses blackness while maintaining production feasibility
Solution Approach 2:
The invention focuses on controlling the local quality of specific impurities (non-nitride silicon, oxygen, carbon) within the silicon nitride powder. By targeting specific compositional aspects rather than overall process complexity, the invention achieves appearance consistency without requiring complete process redesign
2Strength
If the amounts of oxygen and carbon are reduced to improve strength, then sintered compact strength increases, but production complexity increases
Solution Approach 1:
The invention establishes specific parameter thresholds for impurity ratios (R Si /R O ≤ 0.19 and (R Si ×R C )/R O ≤ 2×10 -4) that simultaneously achieve both high strength and white appearance. This dual-parameter control approach consolidates multiple quality requirements into unified compositional specifications
Solution Approach 2:
The invention applies partial action by focusing control on the critical ratio parameters rather than requiring complete elimination of all impurities. This selective control approach achieves the necessary strength and appearance properties without the excessive complexity of total purification
3Strength
If the β-phase percentage is increased to 30-100% to improve bending strength, then bending strength increases, but the appearance consistency becomes problematic
Solution Approach 1:
The invention changes the controlling parameters from phase composition (β-phase percentage) to chemical composition (impurity ratios). By controlling R Si /R O and (R Si ×R C )/R O, the invention simultaneously achieves high bending strength through appropriate phase formation and consistent white appearance by suppressing blackness-causing impurities
Data Source
AI summary
[Problem] To provide a silicon nitride powder having an appearance that is white in color, with suppressed blackness. [Solution] A silicon nitride powder containing silicon nitride, non-nitride silicon, and oxygen, wherein a ratio (RSi/RO) of a mass ratio RSi of non-nitride silicon in the silicon nitride powder with respect to a mass ratio RO of oxygen in the silicon nitride powder is 0.19 or lower.