非氧化物材料的处理.doc

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1、ProcessingofNon-OxideMaterialsOxynitrideGlassesandNitridesINTRODUCTIONMulfingerbubbledtheglassmeltswithN2orNH3gastoremovetheinvolvedwater,andnoticedthatthehardnessofthecooledmeltsorglasseswasincreased,whichwasattributedtothedecreasedamountof=Si-OHgroups,andals

2、opartiallytotheincorporationofnitrogensintotheglassnetwork(Mulfinger,1966).Ontheotherhand,glassyphasesofthesystemssuchasSi-Al-O-NandSi-Y-O-NwerefoundtobeformedinthegrainboundaryregionduringthesinteringofSijN4aidedwithAI2O3and/orY2O3(EvansandSharp,1971).Thesefi

3、ndingshavepromotedthedevelopmentofavarietyofoxynitrideglasses(Ferrandisetal.,1972;Jack,1976;Loehman,1980;JankowskiandRisbud,1980;Sakkaetal.,1983;HomenyandMcGarry,1984).Actually,wenowknowthatthereplacementof2-fdldcoordinatedoxygenatomsby3-foldcoordinatednitroge

4、natomsintheglassnetworkincreasestheconnectivityofthenetworkandimprovesthemechanicalproperties(elasticmodulus,hardnessetc.),andthermalproperties(glasstransitiontemperature,thermalexpansioncoefficientandsoon).Forthefabricationofoxynitrideglasses,besidesthebubbli

5、ngofthemeltswithnitridinggasses,theconventionalmeltingtechniquehasbeenadoptedtoincorporatethenitrogenintotheglassnetworkbyusingnitridessuchasSisNqandAINasrawmaterials.However,toohighmeltingtemperaturesrequired(oftenabove1700°C)causesthedecompositionofnitridesd

6、uringmelting,andlimitedthecontentoftheincorporatednitrogentoafewwt%(WusirikaandChyiing,1980).Twomethodshavebeenproposedtoovercomethisproblem・OneistheheattreatmentofthehighlyporousglassesundertheNH3atmosphere,bywhich3-7wt%nitrogenwasintroducedtothehigh-silicag

7、lassesat950-1050°C(ElmerandNordberg,1967).Theotheristhesol-gelmethod.Inaddition,metalnitrideshavebeenoftechnologicaiimportancebecauseofthehighmeltingpoints(commonly〜3000°C),extremehardness(8〜9orhigherontheMohscale),highchemicaldurabilityandsometimeslusteredcol

8、ors.Consequently,nitrideshavebeenappliedtohightemperaturestmcturematerials,cuttingtoolsandwear-resistantcoatings.Theyhavebeenproducedindifferentshapesbyseveralprocessingtechniques.