DE1210372B - Heat-resistant and oxidation-resistant materials containing molybdenum disilicide - Google Patents
Heat-resistant and oxidation-resistant materials containing molybdenum disilicideInfo
- Publication number
- DE1210372B DE1210372B DEA41393A DEA0041393A DE1210372B DE 1210372 B DE1210372 B DE 1210372B DE A41393 A DEA41393 A DE A41393A DE A0041393 A DEA0041393 A DE A0041393A DE 1210372 B DE1210372 B DE 1210372B
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- Prior art keywords
- resistant
- silicon
- percent
- weight
- molybdenum disilicide
- 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.)
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Links
- 239000000463 material Substances 0.000 title claims description 27
- 230000003647 oxidation Effects 0.000 title claims description 5
- 238000007254 oxidation reaction Methods 0.000 title claims description 5
- YXTPWUNVHCYOSP-UHFFFAOYSA-N bis($l^{2}-silanylidene)molybdenum Chemical compound [Si]=[Mo]=[Si] YXTPWUNVHCYOSP-UHFFFAOYSA-N 0.000 title description 14
- 229910021343 molybdenum disilicide Inorganic materials 0.000 title description 14
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 16
- 229910052710 silicon Inorganic materials 0.000 claims description 14
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 13
- 239000010703 silicon Substances 0.000 claims description 12
- 229910052757 nitrogen Inorganic materials 0.000 claims description 10
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 8
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 8
- 150000004767 nitrides Chemical class 0.000 claims description 6
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 5
- 229910017464 nitrogen compound Inorganic materials 0.000 claims description 5
- 150000002830 nitrogen compounds Chemical class 0.000 claims description 5
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims 1
- 229910052750 molybdenum Inorganic materials 0.000 claims 1
- 239000011733 molybdenum Substances 0.000 claims 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 11
- 239000000377 silicon dioxide Substances 0.000 description 5
- 235000012239 silicon dioxide Nutrition 0.000 description 5
- 239000000440 bentonite Substances 0.000 description 4
- 229910000278 bentonite Inorganic materials 0.000 description 4
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 229910021332 silicide Inorganic materials 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- GPBUGPUPKAGMDK-UHFFFAOYSA-N azanylidynemolybdenum Chemical compound [Mo]#N GPBUGPUPKAGMDK-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical compound [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000010309 melting process Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- -1 silicon oxynitride Chemical class 0.000 description 1
- 239000011863 silicon-based powder Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
- C04B35/597—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon oxynitride, e.g. SIALONS
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/082—Compounds containing nitrogen and non-metals and optionally metals
- C01B21/0821—Oxynitrides of metals, boron or silicon
- C01B21/0823—Silicon oxynitrides
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
- C04B35/58085—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicides
- C04B35/58092—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicides based on refractory metal silicides
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- C—CHEMISTRY; METALLURGY
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- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
- C04B35/584—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride
- C04B35/591—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride obtained by reaction sintering
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/64—Burning or sintering processes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/10—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor
- H05B3/12—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material
- H05B3/14—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material the material being non-metallic
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- Structural Engineering (AREA)
- Inorganic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Ceramic Products (AREA)
Description
Hitzebeständige und oxydationsfeste Materialien, die Molybdändisilicid enthalten Die vorliegende Erfindung bezieht sich auf ein hitzebeständiges und oxydationsfestes Material', welches Molybdändisilicid und gegebenenfalls eine Oxydkomponente enthält. Geformte Körper aus solchem Material sind unter anderem als elektrische Widerstandselemente für ein Temperaturgebiet von 1400 bis 1700'C benutzt worden. Derartige Elemente bieten mancherlei Vorteile, aber sie zeigen eine vermehrte Brüchigkeit beim Abkühlen, nachdem sie einige Zeit in dem Temperaturbereich gehalten worden sind, in welchem die Oxydkomponente eine Rekristallisation oder einen- Schmelzprozeß erfährt. Ein Gebiet von besonderer Bedeutung für die vorliegende Erfindung stellen gesinterte Körper dar, bei denen die Oxydkomponente geschmolzenen Bentonit enthält. Es wurde,gefunden, erhöhtem Maße brüchig daß derartige sind, Körper wenn sie in aus besonders einem Temperaturgebiet von etwa 1300 bis 1500'C abgekühlt werden.Heat-Resistant and Oxidation-Resistant Materials Containing Molybdenum Disilicide The present invention relates to a heat-resistant and oxidation-resistant material which contains molybdenum disilicide and optionally an oxide component. Shaped bodies made of such a material have been used, among other things, as electrical resistance elements for a temperature range from 1400 to 1700 ° C. Such elements offer several advantages, but they exhibit increased brittleness on cooling after having been held for some time in the temperature range in which the oxide component undergoes recrystallization or a melting process. An area of particular concern to the present invention is sintered bodies in which the oxide component contains molten bentonite. It has been found that such bodies are more fragile when they are cooled in a temperature range from about 1300 to 1500 ° C. in particular.
Es war bisher nicht möglich, den Grund für dieses Prüchigwerden eindeutig festzustellen; es kann jedoch angenommen werden, daß diese Erscheinung in gewissem Zusammenhang mit der Tatsache steht, daß das Silicid in der Oxydkoinponente gegen Rekristallisationsvorgänge besonders empfindlich ist.So far it has not been possible to unambiguously identify the reason for this examination determine; however, it can be assumed that this phenomenon is to a certain extent It is related to the fact that the silicide in the oxide component is against Recrystallization processes are particularly sensitive.
Überraschenderweise wurde nun gefunden, daß ein Zusatz von Stickstoff in geeigneter Form die Neigung zum Brüchigwerden verhindert. Um dieses vorteilhafte Ergebnis zu erzielen, soll der Stickstoff in Form einer solchen Stickstoffverbindung zugesetzt werden, die hohen Temperaturen in Gegenwart von Luft widersteht. Dies sind in erster Linie gewisse Nitride.Surprisingly, it has now been found that the addition of nitrogen in a suitable form prevents the tendency to become brittle. To this beneficial To achieve this result, the nitrogen should be in the form of such a nitrogen compound can be added that can withstand high temperatures in the presence of air. this are primarily certain nitrides.
Bei der Verwendung gemäßigter Temperaturen, wie beispielsweise höchstens 1500'C, ist es möglich, das gewünschte Ergebnis dadurch zu erzielen, daß man den Stickstoff in Form von Siliciumnitrid der Formel Si.N4 zusetzt. Aber diese Verbindung ist in oxydierender Atmosphäre bei Temperaturen über 1400'C nicht beständig.When using moderate temperatures, such as a maximum of 1500 ° C., it is possible to achieve the desired result by adding the nitrogen in the form of silicon nitride of the formula Si.N4. But this compound is not stable in an oxidizing atmosphere at temperatures above 1400'C.
Das hitzebeständige oxydationsfeste Material gemäß der Erfindung, welches vorzugsweise als elektrisches WiderstandselementbeiTemperaturen oberhalb 1400'C benutzt werden soll und welches aus Molybdändisilicid, Nitrid und einer Siliciumoxyd enthaltenden Komponente besteht, jedoch von Siliciumcarbid frei ist, enthält als neues kennzeichnendes Merkmal mindestens 0,01 Gewichtsprozent Stickstoff in Form .einer Stickstoffverbindung, die bei hohen Temperaturen an der Luft beständig ist, wobei jedoch etwa anwesendes Siliciumnitrid der Formel Si"N4 höchstens 1 Gewichtsprozent des Materials ausmachen soll.The heat-resistant, oxidation-resistant material according to the invention, which is preferably to be used as an electrical resistance element at temperatures above 1400'C and which consists of molybdenum disilicide, nitride and a silicon oxide-containing component, but is free of silicon carbide, contains at least 0.01 percent by weight of nitrogen as a new characteristic in the form of a nitrogen compound which is stable at high temperatures in air, but any silicon nitride of the formula Si "N4 present should not make up more than 1 percent by weight of the material.
Es sind bereits Formkörper aus Siliciden und Nitriden bekanntgeworden, welche stets Siliciumcarbid als Hauptbestandteil der Masse enthalten. Demgegenüber handelt es sich bei der Erfindung um solche Massen, die keinerlei Siliciumearbid enthalten, sondern praktisch nur aus Molybdändisilicid, Nitrid und Bentonit aufgebaut sind.Moldings made of silicides and nitrides have already become known, which always contain silicon carbide as the main component of the mass. In contrast In the case of the invention, it is a matter of such masses that do not contain any silicon carbide contained, but practically only made up of molybdenum disilicide, nitride and bentonite are.
Ein derartiges Material besitzt gegenüber den bekannten siliciumcarbidhaltigen Massen wesentliche Vorteile. Siliciumcarbidhaltige Massen leiden nämlich an hoher Porosität. Dies bedeutet eine erhebliche Empfindlichkeit gegenüber Sauerstoff, besonders in der Hitze. Aus diesem Grunde läßt sich ein siliciumcarbidhaltiges Material in der Hitze nicht verformen. Überdies zeigt ein solches Material den erheblichen Übelstand, daß in gewissen Temperaturgebieten der Temperaturkoeffizient des elektrischen Widerstandes negativ wird. Diese Instabilität stellt einen erheblichen Nachteil bei Verwendung des Materials für elektrische Widerstände dar. Ganz allgemein halten siliciumcarbidhaltige Massen nur eine beträchtlich niedrigere Temperatur aus als die Massen gemäß der Erfindung.Such a material has compared to the known silicon carbide-containing Masses of substantial advantages. Silicon carbide-containing masses namely suffer from high Porosity. This means a considerable sensitivity to oxygen, especially in the heat. For this reason, a silicon carbide-containing material can be used in Do not deform the heat. Moreover, such a material shows the considerable inconvenience that in certain temperature areas the temperature coefficient of the electrical resistance becomes negative. This instability is a significant disadvantage in use of the material for electrical resistances. In general, silicon carbide-containing The masses only have a considerably lower temperature than the masses according to FIG Invention.
Aus diesen Gründen ist das Material gemäß der Erfindung den bekannten Massen wesentlich überlegen. Die Menge des Siliciumoxynitrids soll mindestens 0,05 Gewichtsprozent, vorzugsweise mindestens 0,2 Gewichtsprozent, betragen. Wenn ein Nitrid der Formel Si,N, in dem Material in merklicher Menge anwesend ist, ist das Material nicht genügend oxydationsfest. Es ist daher wichtig, daß die Menge an Si,N, so gering ist, daß seine Anwesenheit vernachlässigt werden kann; in jedem Fall soll sie unter 1 Gewirlitsprozent des Materials liegen.For these reasons, the material according to the invention is significantly superior to the known masses. The amount of silicon oxynitride should be at least 0.05 percent by weight, preferably at least 0.2 percent by weight. If a nitride of the formula Si, N, is present in the material in a significant amount, the material will not be sufficiently resistant to oxidation. It is therefore important that the amount of Si, N, be so small that its presence can be neglected; in any case, it should be less than 1 percent by weight of the material.
Auch wenn die gesinterten Körper außer Molybdändisilicid noch einen wesentlichen Anteil einer Oxydkomponente aufweisen, -welche Siliciumdioxyd enthält, bietet die vorliegende Erfindung einen weiteren Vorteil. Nachdem solche Körper längere Zeit bei Temperaturen innerhalb des Gebietes von 1400 bis 1700'C verwendet worden sind, vermindert sich ihre. mechanische Festigkeit in beträchtlichem Maße. Dies steht in gewissem Zusammenhang mit der Tatsache, daß bei hohen Temperaturen die Oxydkomponente das Kornwachstum der Silicidkomponente nicht verhindern kann, ein Vorgang, der das Material brüchiger macht. Überraschenderweise hat sich ergeben, daß der Zusatz von Siliciumoxynitrid, gemäß vorliegender Erfindung, diesen Übelstand beseitigt und zu Körpern aus Molybdändisilicid und einer Oxydkomponente führt, die auch nach dem Erhitzen für längere Zeit auf 1700'C ihre hohe mechanische Festigkeit behalten.Even if, in addition to molybdenum disilicide, the sintered bodies also have a substantial proportion of an oxide component, which contains silicon dioxide, the present invention offers a further advantage. After such bodies have been used for an extended period of time at temperatures within the range of 1400 to 1700'C , their decrease. mechanical strength to a considerable extent. This is somewhat related to the fact that at high temperatures the oxide component cannot prevent the grain growth of the silicide component, a process which makes the material more fragile. Surprisingly, it has been found that the addition of silicon oxynitride, according to the present invention, eliminates this drawback and leads to bodies made of molybdenum disilicide and an oxide component which retain their high mechanical strength even after heating for a long time at 1700.degree.
Die vorliegende Erfmdung bezieht sich insbesondere auf elektrische Widerstandselemente, die in der Hauptsache aus Molybdändisilicid und einer Siliciumdioxyd enthaltenden Oxydkomponente zusammen- gesetzt sind. Als stickstoffhaltiger Zusatz wird in erster Linie die Verwendung von Siliciumoxynitrid empfohlen. Aber die Erfindung ist nicht auf den Zusatz dieses Nitrids zu den Molybdändisilicid enthaltenden Ausgangsmaterialien beschränkt. Es können auch andere stickstoffhaltige Verbindungen, die in der Luft bei hohen Temperaturen beständig - sind, als Zusatzmittel verwendet werden.The present invention relates in particular to electrical resistance elements which are composed mainly of molybdenum disilicide and an oxide component containing silicon dioxide. The use of silicon oxynitride is primarily recommended as a nitrogen-containing additive. But the invention is not limited to the addition of this nitride to the starting materials containing molybdenum disilicide. There may be other nitrogen-containing compounds stable in air at high temperatures - are, be used as additives.
Im folgenden wird die Erfindung unter Bezugnahme auf ein Beispiel näher beschrieben. Beispiel Siliciumoxynitrid der Formel Si2N0 wird hergestellt, indem man eine Mischung von 200 g Siliciumpulver, das eine Korngröße von 75 Mikron aufweist, und 32 g Natriumhydroxyd 48 Stunden lang bei 1400'C in einer Atmosphäre aus Stickstoff und Argon im Verhältnis 1: 1 erhitzt. Das erhaltene Produkt wird dann in einer Mischung aus Fluorwasserstoffsäure der Formel HF und Salpetersäure der Formel HNO" ausgelaugt und enthält daraufhin lediglich Spuren von Silicium und Siliciumnitrid der Formel Si3N4. Man stellt nun eine Mischung aus 1 Gewichtsprozent des erhaltenen Oxynitrids und 94 Gewichtsprozent fein-# verteiltem Molybdändisilicid und Bentonit in Form einer wäßrigen- Aufschlämmung in einer Menge von 5 Gewichtsprozent, berechnet auf das Trockengewicht, her. Die Mischung- wird dann in Form von elektrischen Widerstandselementen ausgepreßt. Diese werden an- ' fänglich in Wasserstoff bei 1200'C 30 Minuten lang und dann in Luft bei 1550'C 2 Minuten lang gesintert. Nach der endgültigen Sinterung- besitzt das Material eine Biegefestigkeit von 42 kg pro Quadratmillimeter. Nachdem das Material in Luft bei 1430'C 5 Tage lang erhitzt worden war, hatte seine Festigkeit auf 34 kg pro Quadrafmillimeter abgenommen. Demgegenüber war bei dem entsprechenden Vergleichsmaterial aus Molybdändisilicid und Bentonit, das jedoch kein Siliciumoxynitfid enthielt, die Festigkeit unter entsprechenden Bedingungen von 42 Quadratmillimeter auf 8 kg pro Quadratmilliineter gesunken.The invention is described in more detail below with reference to an example. Example Silicon oxynitride of the formula Si2N0 is prepared by heating a mixture of 200 g of silicon powder with a grain size of 75 microns and 32 g of sodium hydroxide for 48 hours at 1400 ° C. in an atmosphere of nitrogen and argon in a ratio of 1: 1 . The product obtained is then leached in a mixture of hydrofluoric acid of the formula HF and nitric acid of the formula HNO "and then contains only traces of silicon and silicon nitride of the formula Si3N4. A mixture of 1 percent by weight of the oxynitride obtained and 94 percent by weight of fine divided molybdenum disilicide and bentonite in the form of a wäßrigen- slurry in an amount of 5 percent by weight, calculated on the dry weight forth. the Mischung- is then extruded in the form of electrical resistance elements. These are turned 'fänglich in hydrogen at 1200'C 30 minutes long long sintered and then in air at 1550'C for 2 minutes. After the final Sinterung- the material has a flexural strength of 42 kg per square millimeter. After the material had been heated in air at 1430'C for 5 days, its strength had to 34 kg lost per square millimeter With molybdenum disilicide and bentonite, which, however, did not contain silicon oxynite fide, the strength decreased from 42 square millimeters to 8 kg per square millimeter under the same conditions.
Nach weiterer Erhitzung auf 1500 bis 1700'C erfuhr das Material gemäß dem obigen Beispiel, das einen Zusatz von 1 Gewichtsprozent Siliciumoxynitrid aufwies, keine weitere Verminderung seiner mechanischen Festigkeit, und zwar selbst nicht nach einer Erhitzungsdauer von mehreren 1000 Stunden. - Der Stickstoffzusatz, gemäß der vorliegenden Erfindung, soll mindestens 0,01 Gewichtsprozent des Materials betragen. Eine obere Grenze für den Stickstoffzusatz kann nicht angegeben werden, da bestimmte Stickstoffverbindungen, wie Siliciumoxynitrid, selbst ein Material von außerordentlicher Hitzebeständigkeit und Korrosionsfestigkeit darstellen. Die Erfindung -umfaßt also auch Körper, die in erheblicher Menge, beispielsweise bis zu 70 Gewichtsprozent etwa, aus Siliciumoxynitrid bestehen und Molybdändisilicid und Siliciumdioxyd lediglich in geringeren Mengen enthalten.After further heating to 1500 to 1700 ° C. , the material according to the above example, which had an addition of 1 percent by weight silicon oxynitride, did not experience any further reduction in its mechanical strength, even after a heating period of several 1000 hours. - The addition of nitrogen, according to the present invention, should be at least 0.01 percent by weight of the material. An upper limit for the addition of nitrogen cannot be given since certain nitrogen compounds, such as silicon oxynitride, are themselves a material of excellent heat resistance and corrosion resistance. The invention thus also includes bodies which consist of silicon oxynitride in considerable amounts, for example up to 70 percent by weight, and only contain molybdenum disilicide and silicon dioxide in smaller amounts.
Im Hinblick auf die spezielle Ausführungsform der Erfindung, wie sie in dem vorgenannten Beispiel beschrieben ist, ist es günstig, zwischen 0,25 und 1 Gewichtsprozent von Siliciumoxynitrid einer Mischung aus Molybdändisilicid und Siliciumdioxyd zuzusetzen. Um jedoch den spezifischen elektrischen Widerstand zu erhöhen, können auch Oxyde, vorzugsweise Siliciumdioxyd, in Form von Glas in solch großer Menge zugegeben werden, daß das Material neben dem Molybdändisilicid und dem Nitrid auch, noch 0,5 bis 40 Gewichtsprozent Oxyd enthält.In view of the particular embodiment of the invention as described in the above example, it is beneficial to add between 0.25 and 1 percent by weight of silicon oxynitride to a mixture of molybdenum disilicide and silicon dioxide. However, in order to increase the specific electrical resistance, oxides, preferably silicon dioxide, can be added in the form of glass in such a large amount that the material also contains 0.5 to 40 percent by weight of oxide in addition to the molybdenum disilicide and the nitride.
Claims (3)
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| Application Number | Priority Date | Filing Date | Title |
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| SE1210372X | 1961-10-19 |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2406275A (en) * | 1942-04-07 | 1946-08-20 | Wejnarth Axel Richard | Electrical resistance element |
| US2412373A (en) * | 1943-11-27 | 1946-12-10 | Wejnarth Axel Richard | Electrical resistance elements durable at high temperatures and proof against chemical action, and process of making same |
| US2412374A (en) * | 1943-11-27 | 1946-12-10 | Wejnarth Axel Richard | Electrical resistance elements durable at high temperatures and proof against chemical action, and process of making same |
| US2445296A (en) * | 1942-10-20 | 1948-07-13 | Wejnarth Axel Richard | Process of manufacturing resistance elements durable at high temperature and proof against chemical action |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2406275A (en) * | 1942-04-07 | 1946-08-20 | Wejnarth Axel Richard | Electrical resistance element |
| US2445296A (en) * | 1942-10-20 | 1948-07-13 | Wejnarth Axel Richard | Process of manufacturing resistance elements durable at high temperature and proof against chemical action |
| US2412373A (en) * | 1943-11-27 | 1946-12-10 | Wejnarth Axel Richard | Electrical resistance elements durable at high temperatures and proof against chemical action, and process of making same |
| US2412374A (en) * | 1943-11-27 | 1946-12-10 | Wejnarth Axel Richard | Electrical resistance elements durable at high temperatures and proof against chemical action, and process of making same |
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