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The present invention provides methods for making a microporous ceramic material using a metal silicon powder and including a reaction sintering process of the silicon. A material for forming a microporous ceramic material used in these methods includes a metal silicon powder, a silicon nitride powd

The present invention provides methods for making a microporous ceramic material using a metal silicon powder and including a reaction sintering process of the silicon. A material for forming a microporous ceramic material used in these methods includes a metal silicon powder, a silicon nitride powder and/or a silicon carbide powder, and if desired, a yttrium oxide powder and/or an aluminum oxide powder. These methods can make a microporous ceramic material that can be used preferably as a gas or liquid filter, a catalyst carrier or a support of a gas separation membrane.

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What is claimed is: 1. A microporous ceramic substrate of a gas separation membrane, the substrate comprising primarily alpha-silicon nitride; containing essentially no needle-like beta-silicon nitride; having a maximum of micropore size distribution at or an average micropore size of 0.5 μm o

What is claimed is: 1. A microporous ceramic substrate of a gas separation membrane, the substrate comprising primarily alpha-silicon nitride; containing essentially no needle-like beta-silicon nitride; having a maximum of micropore size distribution at or an average micropore size of 0.5 μm or greater, but less than 2 μm; and having a porosity of 30% or greater, but less than 40%, and wherein the substrate is produced by a manufacturing process comprising the steps of: (A) preparing a starting material containing silicon nitride power and metal silicon powder at a mass ratio of 100 parts of silicon nitride to between 10 and 100 parts of metal silicon; and further containing yttrium oxide powder and aluminum oxide powder at a molar fraction of yttrium oxide to aluminum oxide (Y2O3/Al2O3) in a range from 0.9 to 1.1 and each at 2% by mass or greater, but less than 250% by mass of the amount of metal silicon powder, and yet not exceeding 20% by mass of the total amount of the starting material, (B) molding the starting material into a prescribed shape; and (C) subjecting the molded product of the prescribed shape to reaction sintering at a temperature from 1200° C. to 1500° C. in an atmosphere that allows nitrization. 2. A microporous ceramic substrate according to claim 1 having a three-point bending strength of 40MPa or greater when measured at 800° C. according to JIS (R1601). 3. A microporous ceramic substrate according to claim 1 containing yttrium oxide and aluminum oxide at a molar fraction Y2O3/Al2O3 in a range from 0.9 to 1.1. 4. A microporous ceramic substrate according to claim 1, wherein the molded product is heated from room temperature to a temperature of 700° C. or higher, but lower than 900° C. at a temperature increase rate of 5° C./minute or greater, but less than 7° C./minute; is further heated to a temperature of 1200° C. or higher at a temperature increase rate of 1° C./minute or greater, but less than 5° C./minute; and is stored at a temperature between 1200° C. to 1500° C. for 2 hours or more, but less than 10 hours. 5. A microporous ceramic substrate according to claim 1, wherein the average particle size of silicon nitride powder and that of metal silicon powder are both in a range from 1 μm to 50 μm; and the average particle size of yttrium oxide powder and that of aluminum oxide powder are in a range from 0.1 μm to 1 μm. 6. A microporous ceramic substrate according to claim 1, wherein the starting material is molded with applied pressure from 100 MPa to 200 MPa. 7. A microporous ceramic substrate according to claim 6 having a three-point bending strength of 50 MPa or greater when measured at 800° C. according to JIS (R1601).