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WO1990008102A1 - Procede et appareil pour produire des cristaux de carbure de bore - Google Patents

Procede et appareil pour produire des cristaux de carbure de bore Download PDF

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Publication number
WO1990008102A1
WO1990008102A1 PCT/US1989/005871 US8905871W WO9008102A1 WO 1990008102 A1 WO1990008102 A1 WO 1990008102A1 US 8905871 W US8905871 W US 8905871W WO 9008102 A1 WO9008102 A1 WO 9008102A1
Authority
WO
WIPO (PCT)
Prior art keywords
hot zone
furnace
boron carbide
nitrogen
feed tube
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.)
Ceased
Application number
PCT/US1989/005871
Other languages
English (en)
Inventor
William G. Moore
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dow Chemical Co
Original Assignee
Dow Chemical Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Dow Chemical Co filed Critical Dow Chemical Co
Priority to JP90503055A priority Critical patent/JPH03503158A/ja
Priority to KR1019900701997A priority patent/KR910700196A/ko
Priority to FI904446A priority patent/FI904446A7/fi
Publication of WO1990008102A1 publication Critical patent/WO1990008102A1/fr
Priority to NO90903938A priority patent/NO903938L/no
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/32—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air
    • C01B3/34—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents
    • C01B3/36—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents using oxygen or mixtures containing oxygen as gasifying agents
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/90—Carbides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/90—Carbides
    • C01B32/914—Carbides of single elements
    • C01B32/991—Boron carbide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer

Definitions

  • This invention relates to a method and apparatus for producing boron carbide crystals. More specifically, the invention is directed to the production of boron carbide crystals of a submicron size.
  • Boron carbide is a ceramic material having a high degree of hardness, good structural integrity at high temperatures, and chemical inertness. These properties make boron carbide a useful material for fabricating devices such as armor plating, sand blasting nozzles, bearings, dies, control rods for nuclear reactors, and refractory liners. In many of these applications it is desirable to use a high purity, monodispersed, boron carbide powder in which the crystals are less than one (1) micrometer in size. The narrow particle size distribution gives the product certain advantages. One advantage is optimum reactivity.
  • the material can be , hot-pressed to yield a uniform, fine-grained material that is free of pores, excess carbon, and low melting metallic carbide impurities.
  • the usual method for producing boron carbide crystals is to place a particulate mixture of a boric oxide compound and a carbon compound in a crucible and pass the crucible through the hot zone of a high temperature furnace.
  • a major problem with this method is that the mixture is heated to its reaction temperature at a rate which produces only a very broad range of crystals in the micron size range, and essentially no crystals that are smaller than one (1) micrometer in size.
  • the invention is directed to an apparatus and method for producing a quantity of boron carbide crystals in which a major portion of the crystals are of sub-micrometer size.
  • the apparatus used in the practice of this invention is a modified version of a graphite resistance push-type furnace that operates at extremely high temperatures.
  • the furnace unit includes a floor member and a roof member, with the space between these two members defining a hot zone. Heat is delivered to the hot zone by heater means located Inside the furnace unit adjacent to the roof member.
  • the furnace unit is a vertical feed tube, which Is positioned above the furnace hot zone.
  • the feed tube is designed for feeding a nitrogen-free particulate mixture of a boric oxide compound and a carbon compound into the hot zone.
  • a cooling fluid is circulated around the feed tube, which cools the tube enough to maintain the boric oxide feed compound below its melting point.
  • the furnace unit also includes a group of boat members designed to move along the floor of the furnace hot zone in a path that passes directly below the feed tube.
  • the temperature of the hot zone is maintained above 1570°C. At this temperature the boric oxide compound will react with the carbon compound to form boron carbide crystals. As each boat member moves underneath the the feed tube, the boat is filled with a load of the boron carbide crystals, which are carried in the boat to a collection point outside of the furnace hot zone.
  • Figure 1 is a front elevation view, mostly in schematic, of a high temperature furnace used in making boron carbide according to this invention.
  • FIG. 2 is a detail view, partly in schematic, of components of the furnace " shown in Fig. 1 which are used to feed a starting material for boron carbide into the furnace.
  • the high temperature furnace of this invention is generally designated by the letter F.
  • the outside of the furnace is defined by a metal shell 10.
  • the inside part of the furnace is defined generally by a roof section and a floor member.
  • the roof section consists of three decks, namely, an upper deck 11, intermediate deck 12, and lower deck 13» with the floor member . H being located below deck 13.
  • the roof section decks and the floor member are constructed of graphite.
  • the space between the shell and the roof section, and the shell and the floor member provides an insulation section 15.
  • the insula ⁇ tion section 15 is filled with lampblack 16.
  • the space between the deck 12 and floor member 14 defines the hot zone 17 of the furnace.
  • Heater boards 18, which are fabricated of graphite, are positioned directly above the hot zone 17 in a space 19 between the upper deck 11 and the intermediate deck 12. A DC current is passed through each board as the heating medium.
  • Above the hot zone 17 of the furnace is a
  • the lower part of the chute is defined by a sleeve 20, that fastens into the deck 12 and extends up through deck 11.
  • the upper part of the chute is defined by a
  • sleeve 21 of smaller diameter than sleeve 20.
  • the lower end of sleeve 21 is coupled to the upper end of sleeve 20 by a transition piece 22.
  • the top end of sleeve 21 is fitted with a packing gland 23 and gland nut 23a, which provide a seal assembly.
  • a cooling jacket is mounted lengthwise inside the sleeve 21 of the chute.
  • the jacket is defined by an inside tube 24, which is enclosed within an outside tube 25.
  • a vertical 5 feed tube 26 is mounted lengthwise inside tube 24, and an annulus between these tubes defines a passage 27 for circulating a cooling fluid along the outside of the feed tube.
  • the cooling fluid enters passage 27 through an inlet fitting 28.
  • the starting material for producing boron carbide is a particulate mixture of a boric oxide compound and a carbon compound.
  • a device for feeding the particulate mixture into the feed tube 26 is located above the upper end of the feed tube.
  • one type of feeder device that may be used is a screw feeder 31.
  • An outlet spout 31a on the screw feeder is connected to the top end of a glass sight tube 32 with a flexible coupling 33- At its bottom end the sight tube is connected to the top end of feed tube 26 by another flexible coupling 34.
  • the particulate mixture consisted of a physical blend of technical grade boric acid (U.S. Borax), size -200 mesh (less than 74 micrometers) and 50 percent compressed acetylene carbon black (Gulf Oil Co.). The mixture was blended for 30 minutes in a modified mortar mixer coated with an epoxy film. The mixture was prepared to give an excess of boron over carbon of approximately 20 percent, based on the reaction stoichiometry:
  • the mixture was heated in titanium pans for 3.5 hours at 350°C to dehydrate it to B 2 0 3 + C.
  • the pans measured 2 in. high x 24 in. wide x 72 in. (5 cm x 61 cm x 183 cm) long and they were closed with titanium covers having 1/2 in. (1.3 cm) dia. holes therein to allow water vapor to escape from the mixture during heating. After cooling the dried mixture is loosely agglomerated, but it can be easily broken up into ⁇ 10 mesh (1.68 mm) aggregates.
  • the mixture has a bulk density of about 15 lbs/cu. ft. (240.3 kg/m-3), since it contains a substantial amount of entrapped air.
  • the entrapped air includes about 80 percent N 2 , which is undesire-able because it can react to form boron nitride.
  • a vacuum is pulled on the mixture to deaerate it, and argon is used to fill the evacuated feed mixture.
  • the deaerating step thus reduces the N 2 concentration in the boron carbide product to about 0.3 to 0.4 percent.
  • the nitrogen content of the submicrometer boron carbide crystals can be as high as 1 to 3 percent.
  • the particulate mixture 35 is loaded into a hopper 36, which is mounted on the screw conveyor 31 at the end opposite from the outlet spout 31a.
  • argon as a purge gas, is directed into the hopper through a purge line 37, and into the screw conveyor through a purge line 38.
  • the screw shaft 31b in the conveyor is driven by a motor 39, which has a variable speed drive.
  • the argon purge gas provides an inert environment for the reaction of the boric oxide and carbon compounds in the mixture 35.
  • the mixture 35 moves from the conveyor 31 into the feed tube 26, it passes through the glass sight tube 32.
  • the sight tube thus provides a "window" for the furnace operator to periodically view the flow of the reactive mixture into the furnace, and take corrective action if it becomes necessary.
  • the mixture is delivered into the feed tube at a rate of not more than 0.3 lbs/min. (0.7 kg/min), and preferably 0.1 to 0.2 lbs/min. (0.2-0.4 kg/min).
  • water or some other suitable cooling fluid
  • Cooling the feed tube as described herein keeps the temperature inside the tube below 300°C, which is the softening point of boric anhydride. If the particulate mixture is not cooled as it moves through the feed tube, it will rapidly convert to a semi-liquid phase and plug off the tube. From the feed tube 26, the particulate mixture 35 falls downwardly through the hot zone 17 of furnace F and into a product boat 40, which is being pushed along the floor 14 of the furnace. As shown in Figure 1, there is a continuous string of the product boats, and they are moved by a suitable conveyor system (not shown).
  • the boats are pushed through the hot zone 17 at a rate of about 2 in. to 3 in. per minute (5 to 18 cm/min.).
  • the temperature is about 1500°C.
  • the temperature increases to about 2000°C at the point where the particles fall into the product boats.
  • each product boat 40 passes directly below the discharge end of the feed tube, it is filled with a load of boron carbide crystals, and the product is carried to a collection point (not shown) outside of the hot zone.
  • the hot zone 17 is filled with carbon monoxide and argon gas, to provide a desireable inert environment for the reaction of the starting material to boron carbide.
  • the argon is introduced into the hot zone at two points; one point is through the feed inlet pipe 26, and the other point is at the left end of the zone, as indicated by arrow 42.
  • the argon stream entering the hot zone from. the left end also serves another purpose. This stream moves in a direction countercurrent to the path followed by the product boats 40 as they leave the hot zone.
  • the gas stream thus acts as a barrier to prevent the particles in the mixture 35 from being swept out of the hot zone before the boron carbide reaction is completed.
  • a key to obtaining boron carbide crystals in a sub-micrometer size is to be able to heat the starting material above its initiation reaction temperature very rapidly. In the practice of this invention, therefore, it is critical that the temperature of the hot zone be maintained above 1570°C. Another critical factor is the time it takes to heat the particles above the reaction temperature. In the operation described herein the temperature of the hot zone will be 1600°C to 2100°C and the rate at which the particles are heated as they move through the hot zone is at least 200°C per second.
  • the amount of boron carbide crystals produced was about one (1) pound per hour (0.46 hg/hr), of which about 90 percent by weight of the crystals were of sub-micrometer size. The actual size was 0.1 to 0.3 micrometers.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Carbon And Carbon Compounds (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Ceramic Products (AREA)

Abstract

Dans un procédé et un appareil pour produire des cristaux de carbure de bore, une majeure partie des cristaux sont de taille sub-micrométrique, et les cristaux présentent une faible teneur en azote combiné. Un mélange particulaire exempt d'azote d'un composé d'oxyde borique et d'un composé de carbone (35) est déposé dans la zone chaude d'un four à haute température (17) par un tube d'amenée vertical (26) refroidi par du liquide. Le tube d'amenée est introduit dans le plafond (11) du four. Les particules tombent du tube d'amenée dans les coupelles (40) qui quittent la zone chaude pour aller vers un point de collecte, le long du plancher (14) du four. A mesure que le mélange tombe à travers la zone chaude, il est rapidement chauffé par des éléments chauffants (15) au-dessus de la température de réaction d'amorçage du carbure de bore. On obtient un produit dans lequel la plupart des cristaux de carbure de bore sont d'une dimension inférieure à un (1) micron.
PCT/US1989/005871 1989-01-11 1989-12-27 Procede et appareil pour produire des cristaux de carbure de bore Ceased WO1990008102A1 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
JP90503055A JPH03503158A (ja) 1989-01-11 1989-12-27 炭化硼素結晶を製造するための方法および装置
KR1019900701997A KR910700196A (ko) 1989-01-11 1989-12-27 탄화붕소 결정 생산 방법 및 장치
FI904446A FI904446A7 (fi) 1989-01-11 1989-12-27 Menetelmä ja laite boorikarbidikiteiden valmistusta varten
NO90903938A NO903938L (no) 1989-01-11 1990-09-10 Fremgangsmaate og apparat for fremstilling av borkarbidkrystaller.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US29568289A 1989-01-11 1989-01-11
US295,682 1989-01-11

Publications (1)

Publication Number Publication Date
WO1990008102A1 true WO1990008102A1 (fr) 1990-07-26

Family

ID=23138787

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1989/005871 Ceased WO1990008102A1 (fr) 1989-01-11 1989-12-27 Procede et appareil pour produire des cristaux de carbure de bore

Country Status (8)

Country Link
EP (1) EP0429557A4 (fr)
JP (1) JPH03503158A (fr)
KR (1) KR910700196A (fr)
AU (1) AU621989B2 (fr)
CA (1) CA2007460A1 (fr)
FI (1) FI904446A7 (fr)
IL (1) IL93018A0 (fr)
WO (1) WO1990008102A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002066374A1 (fr) * 2001-02-23 2002-08-29 Norsk Hydro Asa Procede pour effectuer des reactions thermiques entre plusieurs reactifs et four conçu a cet effet
CN113880093A (zh) * 2021-11-24 2022-01-04 郑州嵩山硼业科技有限公司 一种碳化硼生产工艺

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106810261A (zh) * 2017-04-12 2017-06-09 郑州嵩山硼业科技有限公司 一种使用中频炉冶炼碳化硼的方法
CN110357106B (zh) * 2019-08-26 2022-07-29 燕山大学 一种制备纳米孪晶碳化硼粉体的方法
CN114506846B (zh) * 2022-02-15 2023-06-06 厦门金鹭特种合金有限公司 一种超细碳化物的生产方法及生产装置

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1897214A (en) * 1930-05-14 1933-02-14 Norton Co Boron carbide and method of making the same
US2155682A (en) * 1935-11-21 1939-04-25 Norton Co Method of making abrasive metal carbides
US3377141A (en) * 1964-08-26 1968-04-09 Cabot Corp Process for producing metal carbides utilizing a solution treatment prior to reaction
US3379647A (en) * 1966-05-04 1968-04-23 Carborundum Co Metal carbide and boride production
US3535080A (en) * 1969-02-18 1970-10-20 Norton Co Apparatus and method for the continuous furnacing of borides,carbides and silicides
US4017587A (en) * 1969-10-03 1977-04-12 The United States Of America As Represented By The Secretary Of The Navy Boron carbide
US4137295A (en) * 1977-04-20 1979-01-30 Tamers Murry A Carbide production using molten metals as heat source
US4276275A (en) * 1979-05-23 1981-06-30 Yoshinori Ando Process for preparing ultrafine carbide powder
JPS63166709A (ja) * 1986-12-26 1988-07-09 Ibiden Co Ltd 炭化物の製造方法
US4804525A (en) * 1986-04-14 1989-02-14 The Dow Chemical Company Producing boron carbide

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS55113609A (en) * 1979-02-21 1980-09-02 Ibiden Co Ltd Manufacturing apparatus for beta crystallbase silicon carbide
US4529575A (en) * 1982-08-27 1985-07-16 Ibiden Kabushiki Kaisha Process for producing ultrafine silicon carbide powder

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1897214A (en) * 1930-05-14 1933-02-14 Norton Co Boron carbide and method of making the same
US2155682A (en) * 1935-11-21 1939-04-25 Norton Co Method of making abrasive metal carbides
US3377141A (en) * 1964-08-26 1968-04-09 Cabot Corp Process for producing metal carbides utilizing a solution treatment prior to reaction
US3379647A (en) * 1966-05-04 1968-04-23 Carborundum Co Metal carbide and boride production
US3535080A (en) * 1969-02-18 1970-10-20 Norton Co Apparatus and method for the continuous furnacing of borides,carbides and silicides
US4017587A (en) * 1969-10-03 1977-04-12 The United States Of America As Represented By The Secretary Of The Navy Boron carbide
US4137295A (en) * 1977-04-20 1979-01-30 Tamers Murry A Carbide production using molten metals as heat source
US4276275A (en) * 1979-05-23 1981-06-30 Yoshinori Ando Process for preparing ultrafine carbide powder
US4804525A (en) * 1986-04-14 1989-02-14 The Dow Chemical Company Producing boron carbide
JPS63166709A (ja) * 1986-12-26 1988-07-09 Ibiden Co Ltd 炭化物の製造方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP0429557A4 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002066374A1 (fr) * 2001-02-23 2002-08-29 Norsk Hydro Asa Procede pour effectuer des reactions thermiques entre plusieurs reactifs et four conçu a cet effet
CN113880093A (zh) * 2021-11-24 2022-01-04 郑州嵩山硼业科技有限公司 一种碳化硼生产工艺

Also Published As

Publication number Publication date
JPH03503158A (ja) 1991-07-18
IL93018A0 (en) 1990-11-05
AU5036490A (en) 1990-08-13
FI904446A0 (fi) 1990-09-10
AU621989B2 (en) 1992-03-26
CA2007460A1 (fr) 1990-07-11
EP0429557A1 (fr) 1991-06-05
EP0429557A4 (en) 1992-04-22
FI904446A7 (fi) 1990-09-10
KR910700196A (ko) 1991-03-14

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