Molded articles formed of silicon nitride based ceramic and process for producing same

Claim 2

A molded body containing a silicon nitride-based ceramic containing Si and N in amounts providing an atomic ratio N/Si of 0.04 to 3.

Claim 3

A molded body as set forth in claim 1, and having a three-point bending strength of 20 Kg/cm 2 or more.

Claim 4

A molded body as set forth in claim 1, wherein said ceramic further contains at least one element selected from the group consisting of O, C and metals in amounts providing the following atomic ratios:

Claim 5

A molded body as set forth in claim 1, wherein said ceramic contains fine ceramic crystallites having a diameter of 2000 A or less.

Claim 6

A molded body as set forth in claim 1, wherein said ceramic is substantially amorphous in nature.

Claim 7

A molded body as set forth in claim 1, wherein said ceramic is obtained by solidifying and calcining a polysilazane having a number average molecular weight of 100-500,000 and a main skeletal structure having the following recurring units: wherein R l , R 2 and R 3 represent independently from each other hydrogen, a hydrocarbyl group, an alkylsilyl group, an alkylamino group or an alkoxy group.

Claim 8

A molded body as set forth in claim 6, wherein said polysilazane is: (a) one which has a number average molecular weight of 100-50,000 and contains the following recurring unit: wherein R and R 3 have the same meaning as above, (b) a reformed polysilazane having (A) a number average molecular weight of 200-500,000, (B) contents of Si, N and H of 50-70 % by weight, 20-34 % by weight and 5-9 % by weight, respectively; and (C) -SiH 2 - and -SiH 3 groups, the molar ratio of the former to the latter being 2.0:1 to 8.4:1, and is prepared by reacting a solution of a raw material having the following recurring unit: wherein R 1 and R 3 have the same meaning as above in an organic base-containing solvent at a temperature and for a period of time sufficient to polycondensate the raw material, (c) a cross-linked polysilazane having a number average molecular weight of 200-500,000 and an atomic ratio N/Si of at least 0.8 in which N are those which are directly bonded to the Si atoms and containing (A) a recurring unit of the formula -SiH 2 -NH- and (B) one or more cross-linkages of the formula -NH-, -NHNH- or -N(NH 2 )- crosslinking the (̵SiH 2 -NH)̵ n chains, (d) a polymetallosilazane having a metal/silicon atomic ratio of 0.001-30 and a number molecular weight of 200-500,000 and obtained by reacting a raw material having a molecular weight of 100-50,000 and the following recurring unit: wherein R 1 and R 3 have the same meaning as above with a metal alkoxide of the formula M(OR 4 ) n wherein M is a metal of the group Ila, III, VI or V of the Periodic Table, R 4 is hydrogen, an alkyl having 1-20 carbon atoms or an aryl and n is the valence of the metal M with the proviso that at least one of the n number of the R 4 is the alkyl or aryl, (e) one which is composed of the following two recurring units: wherein R 1 and R 3 have the same meaning as above and R 5 represents hydrogen, a hydrocarbyl group, an alkylsilyl group, an alkylamino group or an alkoxy group, and having a degree of polymerization of 5-300, or (f) a polyorganohydrosilazane having a molecular weight of about 200-100,000 and a composition :(RSiHNH)x (RSiH) 1 . 5 N i-x wherein R stands for alkyl, alkenyl, cycloalkyl, aryl, aralkyl, alkylsilyl, alkylamino, alkoxy or a group having a carbon atom directly bonded to the silicon atom of the above formula, and x is a number greater than 0.4 and smaller than 1.

Claim 9

A molded body as set forth in claim 1, further containing a reinforcing material.

Claim 10

A molded body as set forth in claim 8, wherein said reinforcing material is in the form of powder and is homogeneously dispersed in said molded body with said ceramic serving as a matrix.

Claim 11

A molded body as set forth in claim 9, wherein said powder is used in an amount of 0.1-60 % based on the total weight of said ceramic matrix and said powder.

Claim 12

A molded body as set forth in claim 9, wherein said reinforcing material is ceramic powder.

Claim 13

A molded body as set forth in claim 8, wherein said reinforcing material is in the form of powder bound with said ceramic serving as a binder.

Claim 14

A molded body as set forth in claim 12, wherein said powder is used in an amount of 40-99.9 % based on the total weight of said ceramic binder and said powder.

Claim 15

A molded body as set forth in claim 8, wherein said reinforcing material is in the form of fibers dispersed in said molded body with said ceramic serving as a matrix.

Claim 16

A molded body as set forth in claim 14, wherein said fibers are used in an amount of 5-75 % by volume.

Claim 17

A molded body as set forth in claim 8, wherein said reinforcing material is a mixture of fibers and powder, said fibers being dispersed in said molded body with said ceramic serving as a matrix, and said powder being dispersed in said ceramic matrix.

Claim 18

A molded body as set forth in claim 16, wherein said fibers are used in an amount of 5-75 % by volume.

Claim 19

A molded body as set forth in claim 16, wherein said powder is used in an amount of 0.1-60 % based on the total weight of said ceramic matrix and said powder.

Claim 20

A molded body as set forth in claim 16, wherein said reinforcing material is ceramic powder.

Claim 21

A process for producing a molded article, comprising the steps of: filling a mold cavity with a raw material containing a polysilazane having a number average molecular weight of 100-500,000 and a main skeletal structure having the following recurring units: wherein R 1 , R 2 and R 3 represent independently from each other hydrogen, a hydrocarbyl group, an alkylsilyl group, an alkylamino group or an alkoxy group; heating said raw material at a temperature from room temperature to about 400 °C to solidify said polysilazane in said mold cavity; and calcining said solidified product to obtain a molded article formed of a silicon nitride-based ceramic.

Claim 22

A process for producing a molded article, comprising the steps of: filling a mold cavity with a raw material containing a polysilazane having a number average molecular weight of 100-500,000 and a main skeletal structure having the following recurring units: wherein R 1 , R 2 and R 3 represent independently from each other hydrogen, a hydrocarbyl group, an alkylsilyl group, an alkylamino group or an alkoxy group; heating said raw material at a temperature from room temperature to about 400 °C to solidify said polysilazane in said mold cavity; and calcining said solidified product to obtain a molded article formed of a silicon nitride-based ceramic.

Claim 23

A process as set forth in claim 20, wherein said polysilazane is one

Claim 24

(a) which has a number average molecular weight of 100-50,000 and contains the following recurring unit: wherein R 1 and R 3 have the same meaning as above; (b) which has a number average molecular weight of 200-500,000, contents of Si, N and H of 50-70 % by weight, 20-34 % by weight and 5-9 % by weight, respectively; and -SiH 2 - and - SiH 3 groups, the molar ratio of the former to the latter being 2.0:1 to 8.4:1, and is prepared by reacting a solution of a raw material having the following recurring unit: wherein R 1 and R 3 have the same meaning as above in an organic base-containing solvent at a temperature and for a period of time sufficient to polycondensate the raw material; (c) which has a number average molecular weight of 200-500,000 and an atomic ratio N/Si of at least 0.8 in which N are those which are directly bonded to the Si atoms and contains a recurring unit of the formula -SiH 2 -NH- and one or more cross-linkages of the formula -NH-, -NHNH- or -N(NH 2 )-crosslinking the (̵SiH 2 -NH)̵ n chains; (d) which has a metal/silicon atomic ratio of 0.001-30 and a number molecular weight of 200-500,000 and is obtained by reacting a raw material having a molecular weight of 100-50,000 and the following recurring unit: wherein R 1 and R 3 have the same meaning as above with a metal alkoxide of the formula M(OR 4 ) n wherein M is a metal of the group Ila, III, VI or V of the Periodic Table, R 4 is hydrogen, an alkyl having 1-20 carbon atoms or an aryl and n is the valence of the metal M with the proviso that at least one of the n number of the R 4 is the alkyl or aryl; (e) which is composed of the following two recurring units: wherein R 1 and R 3 have the same meaning as above and R 5 represents hydrogen, a hydrocarbyl group, an alkylsilyl group, an alkylamino group or an alkoxy group, and has a degree of polymerization of 5-300; or (f) which has a molecular weight of about 200-100,000 and a composition: (RSiHNH)x (RSiH) 1.5 N 1 -x wherein R stands for alkyl, alkenyl, cycloalkyl, aryl, aralkyl, alkylsilyl, alkylamino, alkoxy or a group having a carbon atom directly bonded to the silicon atom of the above formula, and x is a number greater than 0.4 and smaller than 1.

Claim 25

(a) which has a number average molecular weight of 100-50,000 and contains the following recurring unit: wherein R 1 and R 3 have the same meaning as above; (b) which has a number average molecular weight of 200-500,000, contents of Si, N and H of 50-70 % by weight, 20-34 % by weight and 5-9 % by weight, respectively; and -SiH 2 - and - SiH 3 groups, the molar ratio of the former to the latter being 2.0:1 to 8.4:1, and is prepared by reacting a solution of a raw material having the following recurring unit: wherein R 1 and R 3 have the same meaning as above in an organic base-containing solvent at a temperature and for a period of time sufficient to polycondensate the raw material; (c) which has a number average molecular weight of 200-500,000 and an atomic ratio N/Si of at least 0.8 in which N are those which are directly bonded to the Si atoms and contains a recurring unit of the formula -SiH 2 -NH- and one or more cross-linkages of the formula -NH-, -NHNH- or -N(NH 2 )-crosslinking the (̵SiH 2 -NH)̵ n chains; (d) which has a metal/silicon atomic ratio of 0.001-30 and a number molecular weight of 200-500,000 and is obtained by reacting a raw material having a molecular weight of 100-50,000 and the following recurring unit: wherein R 1 and R 3 have the same meaning as above with a metal alkoxide of the formula M(OR 4 ) n wherein M is a metal of the group Ila, III, VI or V of the Periodic Table, R 4 is hydrogen, an alkyl having 1-20 carbon atoms or an aryl and n is the valence of the metal M with the proviso that at least one of the n number of the R 4 is the alkyl or aryl; (e) which is composed of the following two recurring units: wherein R 1 and R 3 have the same meaning as above and R 5 represents hydrogen, a hydrocarbyl group, an alkylsilyl group, an alkylamino group or an alkoxy group, and has a degree of polymerization of 5-300; or (f) which has a molecular weight of about 200-100,000 and a composition: (RSiHNH)x (RSiH) 1.5 N 1 -x wherein R stands for alkyl, alkenyl, cycloalkyl, aryl, aralkyl, alkylsilyl, alkylamino, alkoxy or a group having a carbon atom directly bonded to the silicon atom of the above formula, and x is a number greater than 0.4 and smaller than 1.

Claim 26

A process as set forth in claim 20, wherein said raw material further contains a ceramic powder so that said ceramic powder is dispersed in a matrix of said silicon nitride-based ceramic.

Claim 27

A process as set forth in claim 22, wherein said ceramic powder is formed of a metal nitride, a metal carbide or a metal oxide.

Claim 28

A process for the production of a fiber-reinforced preceramic, comprising the steps of: impregnating fibers with a liquid contaning a polysilazane having a number average molecular weight of 100-500,000 and a main skeletal structure having the following recurring units: wherein R 1 , R 2 and R 3 represent independently from each other hydrogen, a hydrocarbyl group, an alkylsilyl group, an alkylamino group or an alkoxy group; and solidifying said polysilazane to form a prepreg.

Claim 29

A process for the production of a fiber-reinforced preceramic, comprising the steps of: impregnating fibers with a liquid contaning a polysilazane having a number average molecular weight of 100-500,000 and a main skeletal structure having the following recurring units: wherein R 1 , R 2 and R 3 represent independently from each other hydrogen, a hydrocarbyl group, an alkylsilyl group, an alkylamino group or an alkoxy group; and solidifying said polysilazane to form a prepreg.

Claim 30

A process as set forth in claim 24, wherein said polysilazane is one

Claim 31

(a) which has a number average molecular weight of 100-50,000 and contains the following recurring unit: wherein R 1 and R 3 have the same meaning as above; (b) which has a number average molecular weight of 200-500,000, contents of Si, N and H of 50-70 % by weight, 20-34 % by weight and 5-9 % by weight, respectively; and -SiH 2 - and -SiH 3 groups, the molar ratio of the former to the latter being 2.0:1 to 8.4:1, and is prepared by reacting a solution of a raw material having the following recurring unit: wherein R and R 3 have the same meaning as above in an organic base-containing solvent at a temperature and for a period of time sufficient to polycondensate the raw material; (c) which has a number average molecular weight of 200-500,000 and an atomic ratio N/Si of at least 0.8 in which N are those which are directly bonded to the Si atoms and contains a recurring unit of the formula -SiH 2 -NH- and one or more cross-linkages of the formula -NH-, -NHNH- or -N(NH 2 )-crosslinking the (̵SiH 2 -NH)̵ n chains; (d) which has a metal/silicon atomic ratio of 0.001-30 and a number molecular weight of 200-500,000 and is obtained by reacting a raw material having a molecular weight of 100-50,000 and the following recurring unit: wherein R 1 and R 3 have the same meaning as above with a metal alkoxide of the formula M(OR 4 ) n wherein M is a metal of the group Ila, III, VI or V of the Periodic Table, R 4 is hydrogen, an alkyl having 1-20 carbon atoms or an aryl and n is the valence of the metal M with the proviso that at least one of the n number of the R 4 is the alkyl or aryl; (e) which is composed of the following two recurring units: wherein R 1 and R 3 have the same meaning as above and R 5 represents hydrogen, a hydrocarbyl group, an alkylsilyl group, an alkylamino group or an alkoxy group, and has a degree of polymerization of 5-300; or (f) which has a molecular weight of about 200-100,000 and a composition: (RSiHNH) x (RSiH) 1.5 N 1-x wherein R stands for alkyl, alkenyl, cycloalkyl, aryl, aralkyl, alkylsilyl, alkylamino, alkoxy or a group having a carbon atom directly bonded to the silicon atom of the above formula, and x is a number greater than 0.4 and smaller than 1.

Claim 32

(a) which has a number average molecular weight of 100-50,000 and contains the following recurring unit: wherein R 1 and R 3 have the same meaning as above; (b) which has a number average molecular weight of 200-500,000, contents of Si, N and H of 50-70 % by weight, 20-34 % by weight and 5-9 % by weight, respectively; and -SiH 2 - and -SiH 3 groups, the molar ratio of the former to the latter being 2.0:1 to 8.4:1, and is prepared by reacting a solution of a raw material having the following recurring unit: wherein R and R 3 have the same meaning as above in an organic base-containing solvent at a temperature and for a period of time sufficient to polycondensate the raw material; (c) which has a number average molecular weight of 200-500,000 and an atomic ratio N/Si of at least 0.8 in which N are those which are directly bonded to the Si atoms and contains a recurring unit of the formula -SiH 2 -NH- and one or more cross-linkages of the formula -NH-, -NHNH- or -N(NH 2 )-crosslinking the (̵SiH 2 -NH)̵ n chains; (d) which has a metal/silicon atomic ratio of 0.001-30 and a number molecular weight of 200-500,000 and is obtained by reacting a raw material having a molecular weight of 100-50,000 and the following recurring unit: wherein R 1 and R 3 have the same meaning as above with a metal alkoxide of the formula M(OR 4 ) n wherein M is a metal of the group Ila, III, VI or V of the Periodic Table, R 4 is hydrogen, an alkyl having 1-20 carbon atoms or an aryl and n is the valence of the metal M with the proviso that at least one of the n number of the R 4 is the alkyl or aryl; (e) which is composed of the following two recurring units: wherein R 1 and R 3 have the same meaning as above and R 5 represents hydrogen, a hydrocarbyl group, an alkylsilyl group, an alkylamino group or an alkoxy group, and has a degree of polymerization of 5-300; or (f) which has a molecular weight of about 200-100,000 and a composition: (RSiHNH) x (RSiH) 1.5 N 1-x wherein R stands for alkyl, alkenyl, cycloalkyl, aryl, aralkyl, alkylsilyl, alkylamino, alkoxy or a group having a carbon atom directly bonded to the silicon atom of the above formula, and x is a number greater than 0.4 and smaller than 1.

Claim 33

A process as set forth in claim 24, wherein said liquid further contains finely divided ceramic powder dispersed therein.

Claim 34

A process for producing molded, ceramic article, comprising the steps of: providing a solution of a polysilazane having a number average molecular weight of 100-500,000 and a main skeletal structure having the following recurring units: wherein R l , R 2 and R 3 represent independently from each other hydrogen, a hydrocarbyl group, an alkylsilyl group, an alkylamino group or an alkoxy group; mixing said solution with a finely divided ceramic powder to form a slurry; molding said slurry to form a molded body with said polysilazane serving as a binder; and calcining said molded body to form a molded ceramic article.

Claim 35

A process for producing molded, ceramic article, comprising the steps of: providing a solution of a polysilazane having a number average molecular weight of 100-500,000 and a main skeletal structure having the following recurring units: wherein R l , R 2 and R 3 represent independently from each other hydrogen, a hydrocarbyl group, an alkylsilyl group, an alkylamino group or an alkoxy group; mixing said solution with a finely divided ceramic powder to form a slurry; molding said slurry to form a molded body with said polysilazane serving as a binder; and calcining said molded body to form a molded ceramic article.

Claim 36

A process as set forth in claim 27, wherein said polysilazane is one (a) which has a number average molecular weight of 100-50,000 and contains the following recurring unit: wherein R and R 3 have the same meaning as above; (b) which has a number average molecular weight of 200-500,000, contents of Si, N and H of 50-70 % by weight, 20-34 % by weight and 5-9 % by weight, respectively; and -SiH 2 - and - SiH 3 groups, the molar ratio of the former to the latter being 2.0:1 to 8.4:1, and is prepared by reacting a solution of a raw material having the following recurring unit: wherein R 1 and R 3 have the same meaning as above in an organic base-containing solvent at a temperature and for a period of time sufficient to polycondensate the raw material; (c) which has a number average molecular weight of 200-500,000 and an atomic ratio N/Si of at least 0.8 in which N are those which are directly bonded to the Si atoms and contains a recurring unit of the formula -SiH 2 -NH- and one or more cross-linkages of the formula -NH-, -NHNH- or -N(NH 2 )-crosslinking the + SiH2-NH)̵ n chains; (d) which has a metal/silicon atomic ratio of 0.001-30 and a number molecular weight of 200-500,000 and is obtained by reacting a raw material having a molecular weight of 100-50,000 and the following recurring unit: wherein R 1 and R 3 have the same meaning as above with a metal alkoxide of the formula M(OR 4 ) n wherein M is a metal of the group Ila, III, VI or V of the Periodic Table, R 4 is hydrogen, an alkyl having 1-20 carbon atoms or an aryl and n is the valence of the metal M with the proviso that at least one of the n number of the R 4 is the alkyl or aryl; (e) which is composed of the following two recurring units: wherein R 1 and R 3 have the same meaning as above and R 5 represents hydrogen, a hydrocarbyl group, an alkylsilyl group, an alkylamino group or an alkoxy group, and has a degree of polymerization of 5-300; or (f) which has a molecular weight of about 200-100,000 and a composition: (RSiHNH) x (RSiH) 1 .sN i-x wherein R stands for alkyl, alkenyl, cycloalkyl, aryl, aralkyl, alkylsilyl, alkylamino, alkoxy or a group having a carbon atom directly bonded to the silicon atom of the above formula, and x is a number greater than 0.4 and smaller than 1.