Silicon Nitride Powder Composition for Low-Density, High-Strength Sintering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing silicon nitride sintered bodies are costly to produce and lack the balance of low density and high strength, limiting their application in lightweight, durable structures.
Innovation Solution
A silicon nitride powder with controlled carbon and oxygen content, along with specific surface area and phase composition, is manufactured using a direct nitriding method, promoting β-phase formation and preventing excessive densification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional manufacturing methods are used to produce silicon nitride sintered bodies, then manufacturing cost is reduced, but density increases and strength decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the carbon content (0.03-0.15 mass%) and oxygen content (0.05-0.8 mass%) in the silicon nitride powder, as well as controlling the β-phase content (10-50%) and specific surface area (5-15 m²/g). These parameter optimizations enable the sintered body to achieve both low density (relative density 94% or less) and high strength (bending strength 700 MPa or more), resolving the contradiction between strength and weight.
2Strength
If conventional manufacturing methods are used to produce silicon nitride sintered bodies, then manufacturing cost is reduced, but manufacturing cost increases
Solution Approach 1:
The patent optimizes key parameters including carbon content (0.03-0.15 mass%), oxygen content (0.05-0.8 mass%), β-phase content (10-50%), and specific surface area (5-15 m²/g). By controlling these parameters within specific ranges, the invention achieves high strength (bending strength 700 MPa or more) while enabling cost-effective manufacturing through optimized sintering conditions and material composition, avoiding excessive densification and associated costs.
3Ease of manufacture
If carbon content in silicon nitride powder is increased, then manufacturing cost is reduced, but β-phase generation is suppressed
Solution Approach 1:
The patent precisely controls the carbon content within the range of 0.03-0.15 mass%, which is sufficient to promote β-phase generation (achieving 10-50% β-phase content) during sintering. This optimized carbon level resolves the contradiction by maintaining compositional stability while enabling the desired phase transformation, avoiding both carbon deficiency (which suppresses β-phase) and excessive carbon (which would increase cost and cause other issues).
Solution Approach 2:
The patent utilizes phase transitions by controlling the transformation from α-phase to β-phase during sintering. By optimizing carbon content (0.03-0.15 mass%) and sintering conditions, the invention promotes the generation of β-phase (10-50% content) which has lower density and higher strength. This phase transition mechanism enables the sintered body to achieve low relative density (94% or less) while maintaining high strength, resolving the contradiction between phase composition stability and desired phase distribution.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enables the production of a silicon nitride sintered body with low density and high strength, suitable for lightweight structural applications at reduced manufacturing costs.
Implementation Method 1
since the mass proportion Cs of carbon contained in the surface portion of the powder is equal to or less than the predetermined value, β-phase of silicon nitride is likely to be generated when the powder is used as a sintering material
Implementation Method 2
carbon in the interior portion of the powder forms silicon carbide and is combined with silicon nitride
Data Source
AI summary
Provided is a silicon nitride powder containing silicon nitride and carbon, wherein a mass proportion Cp of carbon with respect to the entire powder is 0.05% or more, and wherein a mass proportion Cs of carbon contained in a surface portion of the powder with respect to the entire powder is 0.05% or less. Provided is a method for manufacturing silicon nitride powder, the method including: molding a kneaded material containing a silicon powder and an organic binder to obtain a molded body, degreasing the molded body by heating the molded body at 900° C. or more and less than 1100° C. for 1 hour or more; firing the molded body in a mixed atmosphere containing nitrogen and at least one selected from a group consisting of hydrogen and ammonia to obtain a fired product containing silicon nitride and carbon; and pulverizing the fired product.