US3692478A - Method of manufacturing silicon carbide whiskers - Google Patents

Method of manufacturing silicon carbide whiskers Download PDF

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Publication number
US3692478A
US3692478A US7593A US3692478DA US3692478A US 3692478 A US3692478 A US 3692478A US 7593 A US7593 A US 7593A US 3692478D A US3692478D A US 3692478DA US 3692478 A US3692478 A US 3692478A
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substrate
whiskers
nucleant
growth
powder
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US7593A
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English (en)
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Wilhelmus Francisc Knippenberg
Gerrit Verspui
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
    • C30B11/04—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method adding crystallising materials or reactants forming it in situ to the melt
    • C30B11/08—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method adding crystallising materials or reactants forming it in situ to the melt every component of the crystal composition being added during the crystallisation
    • C30B11/12—Vaporous components, e.g. vapour-liquid-solid-growth
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10S117/90—Apparatus characterized by composition or treatment thereof, e.g. surface finish, surface coating
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S264/00—Plastic and nonmetallic article shaping or treating: processes
    • Y10S264/19—Inorganic fiber

Definitions

  • the invention relates to the manufacture of whiskers.
  • Whiskers are to be understood to mean herein crystals having a maximum average thickness of 100 ,um. the length of which is at least 10 times larger than the thickness.
  • whiskers can be formed by growing in a gaseous phase on a substrate, a strong anisotropic crystal growth being promoted by nucleation of the substrate, that is to say such a treatment that crystallisation nuclei are formed on places on the substrate surface separated from each other.
  • elongated crystals can be obtained in all kinds of dimensions by using a substance, a so-called nucleant, which stimulates the formation of a local crystallisation nucleus. This is in particular the case in the manufacture of crystal whiskers by VLS-growth.
  • VLS (Vapour-Liquid-Solid) crystal growth has already been described in Transactions of the Metallurgical Society of A.I.M.E. 233. (1965), 1053.
  • a substance to be crystallized or its components
  • a substance nucleant locally provided on a substrate and in which the substance to be crystallized is soluble, and said substance is deposited via the drops on the substrate in the form of elongated crystals.
  • This method is, of course, useful for growing whiskers and, as is known, has been applied for manufacturing whiskers of different substances.
  • a substrate is nucleated by sputtering or vapour-deposition of a substance, from which upon heating prior to or during the crystal growth very fine drops are formed which can each be active separately, as a liquid phase necessary for VLS-growth.
  • nucleant only fulfils a function at the beginning of the crystal growth and is certainly not active as a liquid phase in a VLS-growth during the whole crystal growth.
  • a dense uniform population of the substrate with drops of equal size is not obtained as such in all circumstances.
  • powdered particles which are in contact with each other may flow together, so that in addition to drops which correspond in volume to that of the provided grains, larger drops will also be formed.
  • nucleation is effected by vapourdeposition of a substance, suitable for VLS-growth, followed by heating, the vapour-deposited layer will divide in individual drops but usually the sizes of these drops will vary and, moreover, may form an irregular, poorly dense pattern of crystallisation nuclei on the substrate.
  • the invention relates to a method of growing crystals in the form of whiskers on a substrate in a gaseous atmosphere containing the substance to be crystallized or its components, in which strong anisotropic crystal growth is stimulated by nucleation of the substrate, characterized in that the crystals are grown on a substrate which is rough at least superficially due to the presence of crystallites projecting from the surface the lateral dimensions of said crystallites at said surface approximately corresponding in size to the thickness of the crytsals to be grown.
  • the nucleant may be applied in an elementary form but in that case variations in the choice of the crystallisation circumstances in connection with the volatility of the nucleant, that is to say in the choice of the temperature, the partial pressure of the substance to be crystallized or its components and the overall pressure of the gas atmosphere, are limited.
  • nucleant in the form of a compound which can be converted into a nucleant by disproportioning or other chemical reaction because in that case various substances of a varying volatility are available as a result of which there is a greater possibility of adapting the crystallisation conditions in a correct manner.
  • the formed continuous layer will be divided into separate drops upon heating and form a dense uniform pattern of drops Wind: is determined by the uniformly rough structure of the substrate surface.
  • nucleant or a compound thereof is provided on the substrate in a finely divided form by spraying or smearing.
  • a pattern of drops is formed which is determined by the lateral dimensions of the crystallites in the plane of the substrate surface. This result is even promoted by providing the nucleant in the form of powder of slightly varying grain size and particularly having a gram size which corresponds at most to the said transverse dimensions of the crystallites.
  • the substrates should be constructed from a material which is resistant to the gas atmosphere in which and the temperature at which the crystal growth is carried out.
  • Substrates which consist at least superficially of polycrystalline material of the above crystallite size can be manufactured by sublimation or by gas reactions in which, of course, parameters, such as vapour pressure and temperature, should be suitably chosen so as also to obtain the required roughness.
  • Substrates are preferred, however, which consist of powder agglomerates which can be obtained by sintering, pressing or adhering with a binder in any suitable form, since in the manufacture thereof the crystallite dimensions and the surface roughness can easily be controlled by the choice of the grain size and the grain shape of the starting material.
  • the manufacture of cohering powder agglomerates provides a favourable possibility of forming nucleated substrates in one operation by starting from a powdered substrate material, in which the nucleant or a compound which can be converted to a nucleant is distributed evenly in the form of a powder having a grain size corresponding to the thickness of the crystals to be formed.
  • a particular advantage of powder agglomerates as substrates is that it can simply be obtained by means of a suspension of the raw materials on a support.
  • EXAMPLE 1 A plate of 25 x x 2 mm. is formed by sintering silicon carbide powder having a grain size of 1 am. at 2200 C. for 30 minutes. The plate is then atomized on one side with iron powder having a grain size smaller than 1 ,am. and the excessive iron powder is wiped oif.
  • a substrate 1 thus formed which is nucleated with iron powder 2 in a graphite crucible 3 is placed on a bed of quartz powder 4.
  • the assembly is arranged in a quartz tube 5, through which hydrogen is led at a rate of 1 litre per minute and heated at 1280 C.
  • Whiskers of silicon carbide diameter 1 m., length 2 cm., grow on the substrate in 10 hours.
  • the yield is mgms. of whiskers per plate.
  • EXAMPLE 2 Aluminum oxide powder (pro analysis) having a grain size of 0.01 to 0.1 ,um. is mixed with ethyl acetate and compressed to tablets of 10 x 100 x 1 mm.
  • a few of these tablets 11 serving as substrates and aluminum oxide crucibles 12 filled with aluminum 13 are placed on a bed of quartz grains 14 in an aluminum oxide boat 15.
  • the assembly is surrounded by a tube of aluminum oxide 16 through which a hydrogen current of 1 litre per minute is led, and heated by means of an oven at 1300 C.
  • the substrate is nucleated via the gaseous phase with aluminum.
  • the substrate is dense and uniformly populated with whiskers.
  • the yield is 200 mgms.
  • the substrate used in this example is a commercial product consisting of a graphite plate provided with a grown pyrographite layer of known orange peel structure having projecting graphite cones of approximately 10 am. diameter (Chernie, Ingenieurtechnik, nr. 39, vol. 14 (1967), 833).
  • a plate of 100 x 20 mm. of this material is smeared with powder of carbonyl nickel having a grain size smaller than 1 m.
  • this plate 21 nucleated with nickel is laid on a graphite crucible 22 as a cover in which crucible quartz powder 23 is present.
  • the assembly is arranged in a tube 24 of quartz and a flow of 75% nitrogen with 25% hydrogen is led through at a rate of /2 litre per minute.
  • whiskers of silicon nitride, diameter 10 m, length 10 mm. grow on the lower side of the substrate 21 in a uniformly dense population.
  • EXAMPLE 4 Onto a quartz plate the surface of which is provided with an adhesive layer consisting of a rubber adhesive, a powdered mixture of sand and gold in a weight ratio of 1:10 having a grain size of 30 m is spread and nonadhered powder particles are flicked off. In this manner a monograin layer of sand and gold is formed on the quartz plate.
  • the resulting substrate nucleated with gold is arranged in a quartz tube.
  • a gas-current consisting of hydrogen with 2 mol percent SiCL of 20 litres per hour is led through.
  • EXAMPLE 5 Zirconium oxide powder, having a grain size 1 m is mixed with 1% by weight of Fe O grain size 0.1 m. A suspension of the mixture obtained is spread on a quartz plate in the form of a thin layer.
  • the resulting substrate is arranged in a quartz tube, and a gas current consisting of hydrogen with 3% propane is led through said tube at a rate of 1 litre per min.
  • the iron oxide is converted in a uniformly dense nucleation of iron by the hydrogen upon heating at 1280 C. Furthermore, silicon monoxide is developed from the quartz so that a crystallisation atmosphere containing silicon and carbon is formed, as a result of which whiskers of silicon carbide, having diameters of 0.1 ,uIIL, lengths of 1 cm., grow at the locations of the iron nuclei.
  • a method of growing crystals in the form of whiskers which comprises forming a substrate by sintering silicon carbide powder having a uniform grain size at a temperature of about 2200 C. to form a plate thereof; atomizing the plate on one side with iron powder to nucleate it, said iron powder having a grain size which is smaller than the silicon carbide powder, and wiping ofl any excessive iron powder from the plate; placing the thus formed substrate in a graphite crucible resting on a bed of quartz powder, arranging the crucible with the substrate resting on the quartz powder in a quartz tube, and flowing hydrogen gas heated to a temperature of 1280" C. through the quartz tube; whereby whiskers of silicon carbide having a diameter of 1 micrometer and a length of 2 centimeters are grown on the substrate in response to strong anisotropic crystal growth stimulated by the nucleated substrate.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
US7593A 1969-02-01 1970-02-02 Method of manufacturing silicon carbide whiskers Expired - Lifetime US3692478A (en)

Applications Claiming Priority (1)

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NL6901661A NL6901661A (fr) 1969-02-01 1969-02-01

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US3692478A true US3692478A (en) 1972-09-19

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US (1) US3692478A (fr)
AU (1) AU1084970A (fr)
BE (1) BE745305A (fr)
CA (1) CA927720A (fr)
CH (1) CH558207A (fr)
DE (1) DE2003959A1 (fr)
ES (1) ES376059A1 (fr)
FR (1) FR2033816A5 (fr)
GB (1) GB1296198A (fr)
NL (1) NL6901661A (fr)
SE (1) SE348650B (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4532182A (en) * 1981-12-29 1985-07-30 Atlantic Richfield Company Silicon carbide whisker sheet composites
US4536379A (en) * 1983-06-02 1985-08-20 Graphite Sales, Inc. Production of silicon carbide
US4873069A (en) * 1987-03-09 1989-10-10 American Matrix, Inc. Method for the preparation of silicon carbide whiskers
US4911781A (en) * 1987-05-05 1990-03-27 The Standard Oil Company VLS Fiber growth process
US5404836A (en) * 1989-02-03 1995-04-11 Milewski; John V. Method and apparatus for continuous controlled production of single crystal whiskers

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4532182A (en) * 1981-12-29 1985-07-30 Atlantic Richfield Company Silicon carbide whisker sheet composites
US4634608A (en) * 1981-12-29 1987-01-06 Atlantic Richfield Company Method of making silicon carbide whisker sheet composites
US4536379A (en) * 1983-06-02 1985-08-20 Graphite Sales, Inc. Production of silicon carbide
US4873069A (en) * 1987-03-09 1989-10-10 American Matrix, Inc. Method for the preparation of silicon carbide whiskers
US4911781A (en) * 1987-05-05 1990-03-27 The Standard Oil Company VLS Fiber growth process
US5404836A (en) * 1989-02-03 1995-04-11 Milewski; John V. Method and apparatus for continuous controlled production of single crystal whiskers

Also Published As

Publication number Publication date
FR2033816A5 (fr) 1970-12-04
CA927720A (en) 1973-06-05
AU1084970A (en) 1971-08-05
DE2003959A1 (de) 1970-08-06
BE745305A (fr) 1970-07-30
CH558207A (de) 1975-01-31
NL6901661A (fr) 1970-08-04
GB1296198A (fr) 1972-11-15
SE348650B (fr) 1972-09-11
ES376059A1 (es) 1972-05-16

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