CA1231514A - Method of making yttrium silicon oxynitrides - Google Patents
Method of making yttrium silicon oxynitridesInfo
- Publication number
- CA1231514A CA1231514A CA000455790A CA455790A CA1231514A CA 1231514 A CA1231514 A CA 1231514A CA 000455790 A CA000455790 A CA 000455790A CA 455790 A CA455790 A CA 455790A CA 1231514 A CA1231514 A CA 1231514A
- Authority
- CA
- Canada
- Prior art keywords
- mixture
- yttrium silicon
- silicon oxynitride
- si3n4
- sio2
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Ceramic Products (AREA)
Abstract
ABSTRACT
A method of making a powder additive consisting of yttrium silicon oxynitrides, preferably of the Y10Si6O24N2 or YSiO2N phases, is disclosed.
Stoichiometric amounts of Y2O3, SiO2, and Si3N4 are mixed and arranged in intimate reactive contact, the amounts being to form a desired oxynitride according to the formula YaSibOcNd, where a, b, c and d represent the required element parts of the compound in equilibrium with the mixture elements. The mixture is heated in an inert atmosphere to a temperature and for a time sufficient to convert the stoichiometric amounts of the mixture to the desired yttrium silicon oxynitride. The heat agglomerated mixture is then ground to a powder.
A method of making a powder additive consisting of yttrium silicon oxynitrides, preferably of the Y10Si6O24N2 or YSiO2N phases, is disclosed.
Stoichiometric amounts of Y2O3, SiO2, and Si3N4 are mixed and arranged in intimate reactive contact, the amounts being to form a desired oxynitride according to the formula YaSibOcNd, where a, b, c and d represent the required element parts of the compound in equilibrium with the mixture elements. The mixture is heated in an inert atmosphere to a temperature and for a time sufficient to convert the stoichiometric amounts of the mixture to the desired yttrium silicon oxynitride. The heat agglomerated mixture is then ground to a powder.
Description
~3~5~
METHOD OF MAKING YTTRIUM SILICON OXYNITRIDES
The invention relates to the art of making silicon oxynitrides and, more particularly, yttrium silicon oxen rides.
Until recently, the prior art had not made y trim silicon oxynitrides independently so that they could be used as a powder additive for a variety of subsequent chemical processes. Oxynitrides, if formed at all, were formed as a commingled byproduct of heating, such lo as by hot pressing a ternary system of silicon nitride, and two oxides used as hot pressing aids (see US. patents 4,102,698; 4,341,874; and 4,350,771). In each of these patents, a compact of the ternary powder system is sistered to a relatively high density during which lo secondary phases form, which may include oxynitrides. Of course, the process was not aimed at producing an oxynitride that could be extracted for other uses. The high density of the resulting product made it very difficult to separate out any oxynitrides that had been formed and even more difficult to convert the high density sistered product into a reground powder. But, more importantly, the purity and type of second phases produced as a result of such sistering could not ye accurately controlled, and the chemistry constraints imposed by the presence of excess silicon nitride inhibited the formation of desired or selected yttrium silicon oxynitride A recent effort (see USE patent 4,331,771) has been made to produce bonded silicon oxynitrides for utility as a structural material. In this effort, silicon powder and oxides are reacted in the presence of an oxygen/nitrogen atmosphere. The method is designed to provide for a strong and dense oxynitride body required by the utilization of the body, which strength can be obtained only by the presence of impure substances in the oxynitride body.
Whit is needed is a method by which a low density, pure form of the o~ynitride can be made economically for other uses with minimal regrinding ~L231J lo There is a need for a method by which stoichiometrlc amounts of the ingredients needed for a specific oxynitride can be chemically reacted to form the specific compound without byproducts and contaminating chemical reactions.
The invention is a method of making yttrium silicon oxynitrides of the formula YaSibOCNd, by the steps comprising (a) mixing together, in intimate reactive contact, stoichiometric amounts of Yo-yo, Sue, and Sweeney to form a desired yttrium silicon oxynitride where a, by c, and d represent the required element parts of the compound in equilibrium with the mixture element parts (when necessary this requires taking into account the amount of Sue that is present as an oxide coating on the Sweeney); (b) hefting the mixture in an inert atmosphere to a temperature level and for a time sufficient to convert the stoichiometric amounts of the mixture to the desired yttrium silicon oxynitride; and (c) grinding said heat agglomerated mixture to a powder.
It it preferable to heat the mixture to the temperature range of 1500 to 1550C for at least 6 hours to produce low density YloSi6O24N2 (hereafter Lo phase), and to heat the mixture to the temperature range of i600 to 165~C for at least 6 hours to produce DOW density YSiO2N phase (hereafter Ye phase The lower temperature and longer times of heating result in a low density (preferably no greater than Al gm/cm3) for the heated powder. As heating progresses in the nitrogen atmosphere, reaction gases may form (such as So) and form part of the atmosphere. Excess Sue may be needed in the initial charge to account for the So volatilization A preferred method for carrying out the subject invention is as follows.
.~. .
~3LSl~
Yttrium silicon oxynitride, according to the formula YaSibOCNd~ is made by mixing together stoichiometric amounts of YO-YO, Sue, and Sweeney to form a specific yttrium silicon oxynitride compound. The subscripts a, b, c, and d represent the required element parts of the compound equilibrated with the mixture element parts. A preferred oxynitride, having the formula YloSi6O24N2~ can be prepared by the nominal mixing together of 10 parts of YO-YO, 9 parts Sue, and 1 part Sweeney, heating the mixture in a nitrogen atmosphere to a temperature level of 1500-1550C for a period in excess of 6 hours, preferably 7 hours, to a density of about 2 gm/cm3, and then regrinding the heat agglomerated mixture to a powder again. It is desirable that the regrinding be minimal as facilitated by the low density of heated mass and thereby avoid grinding contaminant. The resultant powder is thus useful as a relatively pure chemical additive in the desired crystalline form and phase.
Alternatively, the phase of Y5iO2N may be formed 20 by mixing together 2 parts of YO-YO, 1 part Sue, 1 part Sweeney, and heating the mixture in a nitrogen atmosphere to a temperature level of 1600-1650C for a period in excess of 6 hours,, preferably 8 hours, to a density of approximately 2,0 gm/cm3.
In the above modes, a specific temperature range and s~oichiometric amount was required to make the method operate properly. The purity preferred for the yttrla powder was 99.99~ or greater, for the Sue it was 9g.5~ or greater t and for the Sweeney it was 99.0% or greater. Each of the ingredients preferably should have a particle size of: silicon nitride less than 10 microns and an average particle size of 2-3 microns, YO-YO of 10 microns or less and an average particle size of about 2 microns, and Sue of less than 10 microns and an average of about 2-3 microns. Mixing may be carried out in a milling apparatus which provides homogeneity with little change in particle size.
I, .. .
Preferably, the milled mixture is compacted for ease of handling and placement in a furnace and to ensure intimate reactive contact during firing Ever, the mixture may also be placed in a furnace dish and heated if.
the loose aggregate form with some sacrifice in chemical conversion efficiency.
The mixture or compact is heated in an inert atmosphere without mechanical pressure to convert the ingredients to the oxynitride compound. The furnace is preferably evacuated to a pressure of less than 1 micron and heated at a fast rate, i.e., fry (cry) to 1200F (649C) and preferably even faster (such as cry). The furnace is then filled with gaseous nitrogen mixture, the total 2 and ~2 content of such gaseous mixture being lest than about 4 Pam. The temperature of the furnace is then increased up to the desired target level of, for example, 1500-1550C for making the Lo phase, or to the level of 1600-1650C for making the Ye phase. Some of the Sue may volatilize and form So vapor and may have to be accounted for in the initial charge.
The heat agglomerated mixture is then communed to a loose powder form preferably using a conventional ball milling apparatus. In this apparatus, a batch of the heated agglomerated mixture is broken down by milling media in the form of Sweeney cylinders (1/2" diameter by 1/2" length). The milling may be carried out with a small addition of acetone for 1-6 hours and then heated to remove the acetone.
The invention is illustrated by the following Example:
Example -To form the YloSi6024N2 phase, a 100 gram batch or mixture was prepared consisting of 4.773 grams of Sweeney powder, 76.82 grams of YO-YO powder, and 180399 grams amorphous Sue (without taking into consideration Sue present as an oxide on the Sweeney The mixture was lightly compacted into a BY container, using about 10 psi.
'1 I
-- s The container was placed in a furnace evacuated to micron and heated to 1200F (649C) at a fast rate of cry or higher. The temperature was held for one hour and then relatively pure No gas was added to the furnace.
The container was then heated to 1550C at a rate of cry. The container was held at this temperature for six hours. The container, upon cooling, possessed about 100 grams of a YloSi6024N2 cake. The cake was then ground to a powder forum The resulting powder contains at least 99% of the Lo phase if it is to be useful as a crystalline chemical additive for cutting tool applications. However, for some applications, as low as 75~ conversion may be acceptable.
Deviation from the heating rate, time of heating, and equilibrium temperature conditions in the furnace will cause less than 100% of Lo phase to form.
To make a 100 gram batch of essentially single phase YSiO~, a mixture was prepared consisting of 22.0 grams of Sweeney, 8.7 grams Sue (assumes 2.3% Sue on Sweeney Sue as an oxide layer) and 69.3 grams of YO-YO. The mixture was again hand pressed into a furnace container, heated to 1650C for 6 hours, and cooled down reasonably fast.
The heating may be carried out according to a 5 typical nit riding cycle, but such cycle is not cost effective because extremely long periods of time are required and the conversion to oxynitrides is not as predictable.
METHOD OF MAKING YTTRIUM SILICON OXYNITRIDES
The invention relates to the art of making silicon oxynitrides and, more particularly, yttrium silicon oxen rides.
Until recently, the prior art had not made y trim silicon oxynitrides independently so that they could be used as a powder additive for a variety of subsequent chemical processes. Oxynitrides, if formed at all, were formed as a commingled byproduct of heating, such lo as by hot pressing a ternary system of silicon nitride, and two oxides used as hot pressing aids (see US. patents 4,102,698; 4,341,874; and 4,350,771). In each of these patents, a compact of the ternary powder system is sistered to a relatively high density during which lo secondary phases form, which may include oxynitrides. Of course, the process was not aimed at producing an oxynitride that could be extracted for other uses. The high density of the resulting product made it very difficult to separate out any oxynitrides that had been formed and even more difficult to convert the high density sistered product into a reground powder. But, more importantly, the purity and type of second phases produced as a result of such sistering could not ye accurately controlled, and the chemistry constraints imposed by the presence of excess silicon nitride inhibited the formation of desired or selected yttrium silicon oxynitride A recent effort (see USE patent 4,331,771) has been made to produce bonded silicon oxynitrides for utility as a structural material. In this effort, silicon powder and oxides are reacted in the presence of an oxygen/nitrogen atmosphere. The method is designed to provide for a strong and dense oxynitride body required by the utilization of the body, which strength can be obtained only by the presence of impure substances in the oxynitride body.
Whit is needed is a method by which a low density, pure form of the o~ynitride can be made economically for other uses with minimal regrinding ~L231J lo There is a need for a method by which stoichiometrlc amounts of the ingredients needed for a specific oxynitride can be chemically reacted to form the specific compound without byproducts and contaminating chemical reactions.
The invention is a method of making yttrium silicon oxynitrides of the formula YaSibOCNd, by the steps comprising (a) mixing together, in intimate reactive contact, stoichiometric amounts of Yo-yo, Sue, and Sweeney to form a desired yttrium silicon oxynitride where a, by c, and d represent the required element parts of the compound in equilibrium with the mixture element parts (when necessary this requires taking into account the amount of Sue that is present as an oxide coating on the Sweeney); (b) hefting the mixture in an inert atmosphere to a temperature level and for a time sufficient to convert the stoichiometric amounts of the mixture to the desired yttrium silicon oxynitride; and (c) grinding said heat agglomerated mixture to a powder.
It it preferable to heat the mixture to the temperature range of 1500 to 1550C for at least 6 hours to produce low density YloSi6O24N2 (hereafter Lo phase), and to heat the mixture to the temperature range of i600 to 165~C for at least 6 hours to produce DOW density YSiO2N phase (hereafter Ye phase The lower temperature and longer times of heating result in a low density (preferably no greater than Al gm/cm3) for the heated powder. As heating progresses in the nitrogen atmosphere, reaction gases may form (such as So) and form part of the atmosphere. Excess Sue may be needed in the initial charge to account for the So volatilization A preferred method for carrying out the subject invention is as follows.
.~. .
~3LSl~
Yttrium silicon oxynitride, according to the formula YaSibOCNd~ is made by mixing together stoichiometric amounts of YO-YO, Sue, and Sweeney to form a specific yttrium silicon oxynitride compound. The subscripts a, b, c, and d represent the required element parts of the compound equilibrated with the mixture element parts. A preferred oxynitride, having the formula YloSi6O24N2~ can be prepared by the nominal mixing together of 10 parts of YO-YO, 9 parts Sue, and 1 part Sweeney, heating the mixture in a nitrogen atmosphere to a temperature level of 1500-1550C for a period in excess of 6 hours, preferably 7 hours, to a density of about 2 gm/cm3, and then regrinding the heat agglomerated mixture to a powder again. It is desirable that the regrinding be minimal as facilitated by the low density of heated mass and thereby avoid grinding contaminant. The resultant powder is thus useful as a relatively pure chemical additive in the desired crystalline form and phase.
Alternatively, the phase of Y5iO2N may be formed 20 by mixing together 2 parts of YO-YO, 1 part Sue, 1 part Sweeney, and heating the mixture in a nitrogen atmosphere to a temperature level of 1600-1650C for a period in excess of 6 hours,, preferably 8 hours, to a density of approximately 2,0 gm/cm3.
In the above modes, a specific temperature range and s~oichiometric amount was required to make the method operate properly. The purity preferred for the yttrla powder was 99.99~ or greater, for the Sue it was 9g.5~ or greater t and for the Sweeney it was 99.0% or greater. Each of the ingredients preferably should have a particle size of: silicon nitride less than 10 microns and an average particle size of 2-3 microns, YO-YO of 10 microns or less and an average particle size of about 2 microns, and Sue of less than 10 microns and an average of about 2-3 microns. Mixing may be carried out in a milling apparatus which provides homogeneity with little change in particle size.
I, .. .
Preferably, the milled mixture is compacted for ease of handling and placement in a furnace and to ensure intimate reactive contact during firing Ever, the mixture may also be placed in a furnace dish and heated if.
the loose aggregate form with some sacrifice in chemical conversion efficiency.
The mixture or compact is heated in an inert atmosphere without mechanical pressure to convert the ingredients to the oxynitride compound. The furnace is preferably evacuated to a pressure of less than 1 micron and heated at a fast rate, i.e., fry (cry) to 1200F (649C) and preferably even faster (such as cry). The furnace is then filled with gaseous nitrogen mixture, the total 2 and ~2 content of such gaseous mixture being lest than about 4 Pam. The temperature of the furnace is then increased up to the desired target level of, for example, 1500-1550C for making the Lo phase, or to the level of 1600-1650C for making the Ye phase. Some of the Sue may volatilize and form So vapor and may have to be accounted for in the initial charge.
The heat agglomerated mixture is then communed to a loose powder form preferably using a conventional ball milling apparatus. In this apparatus, a batch of the heated agglomerated mixture is broken down by milling media in the form of Sweeney cylinders (1/2" diameter by 1/2" length). The milling may be carried out with a small addition of acetone for 1-6 hours and then heated to remove the acetone.
The invention is illustrated by the following Example:
Example -To form the YloSi6024N2 phase, a 100 gram batch or mixture was prepared consisting of 4.773 grams of Sweeney powder, 76.82 grams of YO-YO powder, and 180399 grams amorphous Sue (without taking into consideration Sue present as an oxide on the Sweeney The mixture was lightly compacted into a BY container, using about 10 psi.
'1 I
-- s The container was placed in a furnace evacuated to micron and heated to 1200F (649C) at a fast rate of cry or higher. The temperature was held for one hour and then relatively pure No gas was added to the furnace.
The container was then heated to 1550C at a rate of cry. The container was held at this temperature for six hours. The container, upon cooling, possessed about 100 grams of a YloSi6024N2 cake. The cake was then ground to a powder forum The resulting powder contains at least 99% of the Lo phase if it is to be useful as a crystalline chemical additive for cutting tool applications. However, for some applications, as low as 75~ conversion may be acceptable.
Deviation from the heating rate, time of heating, and equilibrium temperature conditions in the furnace will cause less than 100% of Lo phase to form.
To make a 100 gram batch of essentially single phase YSiO~, a mixture was prepared consisting of 22.0 grams of Sweeney, 8.7 grams Sue (assumes 2.3% Sue on Sweeney Sue as an oxide layer) and 69.3 grams of YO-YO. The mixture was again hand pressed into a furnace container, heated to 1650C for 6 hours, and cooled down reasonably fast.
The heating may be carried out according to a 5 typical nit riding cycle, but such cycle is not cost effective because extremely long periods of time are required and the conversion to oxynitrides is not as predictable.
Claims (6)
1. A method of making yttrium silicon oxynitrides according to the formula YaSibOcNd, by the steps comprising:
(a) mixing together, in intimate reactive contact, stoichiometric amounts of Y2O3, SiO2, and Si3N4 to form a desired yttrium silicon oxynitride where a, b, c, and d represent the required element parts of the compound in equilibrium with the mixture element parts, said SiO2 may be present as an oxide coating on said Si3N4;
(b) heating the mixture in an inert atmosphere to a temperature level and for a time sufficient to convert the stoichiometric amounts of the mixture to the desired yttrium silicon oxynitride; and (c) grinding said heat agglomerated mixture to a powder.
(a) mixing together, in intimate reactive contact, stoichiometric amounts of Y2O3, SiO2, and Si3N4 to form a desired yttrium silicon oxynitride where a, b, c, and d represent the required element parts of the compound in equilibrium with the mixture element parts, said SiO2 may be present as an oxide coating on said Si3N4;
(b) heating the mixture in an inert atmosphere to a temperature level and for a time sufficient to convert the stoichiometric amounts of the mixture to the desired yttrium silicon oxynitride; and (c) grinding said heat agglomerated mixture to a powder.
2. The method as in claim 1, in which said atmosphere is comprised of nitrogen.
3. The method as in claim 1, in which said heating is carried out to form a yttrium silicon oxynitride of a density no greater than 2.1 gm/cm3.
4. The method as in claim 1, in which said heating is carried out for a time in excess of six hours.
5. The method as in claim 1, in which the yttrium silicon oxynitride to be formed is Y10Si6O24N2, and said mixture is formed by mixing 10 parts of Y2O3, 9 parts of SiO2, and 1 part of Si3N4, said mixture being heated to a temperature level of 1500-1550°C for a period in excess of six hours to a density of about 2.0 gm/cm3.
6. The method as in claim 1, in which the yttrium silicon oxynitride is comprised of YSiO2N, and said mixture is formed by mixing 2 parts of Y2O3, 1 part of SiO2, and 1 part of Si3N4, said mixture being heated to the temperature of 1600-1650°C for a period in excess of six hours in a nitrogen atmosphere.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US527,643 | 1983-07-19 | ||
| US06/527,643 US4501723A (en) | 1983-07-19 | 1983-07-19 | Method of making yttrium silicon oxynitrides |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1231514A true CA1231514A (en) | 1988-01-19 |
Family
ID=24102341
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000455790A Expired CA1231514A (en) | 1983-07-19 | 1984-06-04 | Method of making yttrium silicon oxynitrides |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1231514A (en) |
| IL (1) | IL72290A (en) |
| MX (1) | MX172891B (en) |
| ZA (1) | ZA844869B (en) |
-
1984
- 1984-06-04 CA CA000455790A patent/CA1231514A/en not_active Expired
- 1984-06-26 ZA ZA844869A patent/ZA844869B/en unknown
- 1984-07-02 MX MX201873A patent/MX172891B/en unknown
- 1984-07-03 IL IL72290A patent/IL72290A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| IL72290A0 (en) | 1984-11-30 |
| ZA844869B (en) | 1985-02-27 |
| MX172891B (en) | 1994-01-18 |
| IL72290A (en) | 1988-05-31 |
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