How Silicon Nitride is Made
AMEDICA processes the world's only medical-grade Silicon Nitride.
Raw materials are received in lot sizes ranging from 50 kgs to 600 kgs.
Acceptable raw materials are subsequently weighed in appropriate portions, batched and attrition milled in water. These operations ensure that the necessary ingredients are thoroughly mixed, and that they achieve the requisite particle size and surface area.
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Components are generally dry machined using conventional CNC mills or lathes. These operations define the geometry of each component. Because they are performed in the pre-fired or "green" state, the machining operations account for shrinkage that will subsequently occur during firing.
Silicon nitride powders are then pressed into near-net-shape components using uniaxial dry pressing, isostatic pressing or a combination of the two. These operations compact the powder to approximately 50% of their final density.
Components are subjected to high temperature sintering, conducted at above 1600°C for the purpose of densifying the components.
Components are hot-isostatically pressed at temperatures above 1600°C and 138 MPa in nitrogen. This operation further increases the density of the components to ~100% of theoretical.
Components are then subjected to a cleaning operation using an abrasive blaster, and either grinded or polished to further define the geometry of the components and ensure that they meet customer tolerance requirements.
The finished parts will packaged so as to protect the product during shipment, and to maintain sterility if the product is to be sold sterile.
Machined, polished and engraved parts are inspected for accuracy and geometric conformance, utilizing both specialized equipment and a visual inspection to ensure accuracy, cosmetic appearance and compliance. Samples are also subjected to an Archimedes density test to ensure that each lot of components meets minimum acceptable specifications.
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After milling, each batch is screened and blended with a press lubricant in preparation for pressing.