METHOD OF PRODUCING POROUS MATERIAL BASED ON SILICON NITRIDE Russian patent published in 2020 - IPC C04B35/591 C04B35/634 C04B38/06 

FIELD: chemistry.

SUBSTANCE: invention relates to production of permeable composite materials based on silicon nitride intended for use as air and fluid filters, porous membranes, sorbents, neutralizer bases, composite elements of catalysts and catalyst supports. Method is implemented in a mode of self-sustained combustion of powders of ferroalloys of ferrosilicon or ferrosilicoaluminium, or wastes of their production. Alloys are preliminarily mixed with a solution of polyvinyl alcohol, the mixture is moulded from workpieces which are subjected to cryostructuring by freezing at temperature below 0° with further defrosting for 4–5 hours at room temperature and drying at 60 °C in vacuum at residual pressure of not more than 0.01 MPa. Components of mixture are taken in ratio, wt. %: ferroalloy powder - 50–70, polyvinyl alcohol - 3–10, water is the rest. Ferroalloy particles are smaller than 100 mcm. Combustion is carried out at pressure of 1–10 MPa. Freezing is performed at minus 0.5–25 °C for 15–20 hours.

EFFECT: method extends the field of application of articles from cheap, accessible ferroalloys without electricity consumption, fastness of the synthesis process, enables to recycle wastes from ferroalloy production, provides high operational characteristics of porous material (compressive strength 37_0–38_3 MPa, porosity 35_5–50_0 %, resistance to dynamic and static loads of articles), obtaining optimum equal porosity of material.

6 cl, 3 ex, 3 dwg, 1 tbl