Classifications

• • 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
  • C01B32/25—Diamond
  • C01B32/26—Preparation

Definitions

• the invention relates to a method of manufacturing synthetic diamond and a device for carrying out this method.
• the invention relates to a process for manufacturing synthetic diamond by recrystallization under pressure of carbon obtained by modification of its allotropic form.
• these pressure recrystallization techniques require the use of multiple presses called cubic presses, comprising several anvils each associated with hydraulic multiplication devices which make it possible to obtain the necessary high pressures.
• These cubic presses are associated with heating means capable of ensuring the rise in temperature and the melting of the metal containing carbon, these heating means being, inter alia, constituted by two of the aforementioned anvils, through which one circulates a very high alternating current to produce powers of several thousand Watts.
• Other types of presses, frame or column can be used, presses in which a punch and a die work along an axis.
• the main object of the invention is to remedy the drawbacks of the above-mentioned prior art by providing a method and a device of simple design, inexpensive and easy to implement.
• the subject of the invention is a process for manufacturing synthetic diamond, characterized in that it comprises the following stages which consist in: providing a mixture comprising carbon and a metal known as a catalyst metal, the carbon being in solution and / or added to the catalyst metal which has a density greater than that of carbon; - provide a container having a wall capable of containing said mixture and of being hermetically closed, this wall having a melting temperature higher than that of the mixture; preheat the container, at a temperature Tl, to expand its wall; heating the mixture to a temperature T2> T1 to liquefy it; pour the mixture in the liquid state into the preheated container to cause further expansion of the wall of the container; close the container tightly; centrifuge the liquid mixture in the container in order to separate the catalyst metal and the carbon, the catalyst metal being brought by its higher density towards the wall of the container while the carbon is brought towards the center and forms at this location a carbon nut , * cooling the container and the mixture until the mixture solidifies, to cause withdrawal of the container and the catalyst
• FIGS. 1 to 16 very schematically represent the different stages of the method according to the invention
• FIG. 17 is a section also schematically showing a device for implementing the method according to the invention
• FIGS. 1 to 16 an embodiment of the method according to the invention will be described below, which consists, according to a first step, of providing a mixture M (FIG. 1) comprising carbon and a metal called catalyst metal, this mixture being placed in a crucible 1.
• a mixture M (FIG. 1) comprising carbon and a metal called catalyst metal
• the carbon can be in solution in the catalyst metal, for example when a steel having a determined carbon content is used.
• This mixture is preferably in the form of a powder. This mixture can be prepared on the production site for the implementation of the process or be acquired from an external supplier.
• the catalyst metal has a density and a mass greater than that of carbon, for reasons which will be explained in more detail below.
• the catalyst metal is a fine carbon steel, typically comprising 2.5% carbon and designated under the reference ASP 60.
• the invention is not limited to this type of catalyst, but is also extends to other metals, such as nickel, having the desired density and mass characteristics.
• the crucible 1 is of conventional design and can for example be made of sintered aluminum oxide, for example AL2O3.
• the crucible 1 which is filled with said mixture is placed in an oven 2 (FIG. 2) which heats the assembly to bring said mixture M to the liquid state.
• oven 2 FOG. 2
• liquid state is meant here a state of the mixture sufficiently fluid so that it can be poured into a container.
• the oven 2 is a conventional oven with front access comprising an enclosure 4 which can be closed by a door 6 and in which is housed a sliding bottom 8 of the drawer type, on which the crucible 1 can be placed.
• Other types of oven for example a pot oven, can be used for the implementation of this heating step.
• the heating of the mixture M in the enclosure 4 of the oven 2 takes place under a neutral atmosphere, for example in the presence of an inert gas, such as Argon, in order to avoid any physico-chemical modification or alteration of the mixture M .
• an inert gas such as Argon
• a container 10 (FIG. 3) is provided with a wall 12 capable of containing the mixture M in the liquid state.
• the wall 12 is made of a material having a melting temperature higher than that of the mixture M.
• the wall 12 of the container 10 is made of a cast iron having the above qualities.
• the container 10 consists for example of a spherical body 14 delimited by the wall 12.
• the spherical body 14 has an internal diameter D.
• the container 10 has a filling opening 16 which is formed in the body 14 and which extends into an elongated cylindrical neck 18 made integrally with the wall 12 and extending from the body 14 along a first radial axis RI of said body.
• the container 10 is advantageously provided with means for guiding in rotation 20a, 20b and with means for driving in rotation 20c which will be described in more detail below.
• FIG. 4 After having provided the container 10, it is placed in an oven 22 (FIG. 4) in which this container is preheated to a temperature T1 in order to obtain (FIG. 5) a first expansion of the wall 12. Au during this preheating step, the wall 12 expands and the inside diameter of the body increases to an inside diameter D2.
• the oven 22 shown in Figures 4 and 5 is of the same type as the oven 2 in Figure 2 and whose same elements have been designated for all these figures by the same reference numerals.
• the container 10 is held in position by a positioning support 24 resting on the sliding bottom 8 of the oven 22.
• the container 10 is preheated to a temperature of the order of 850 ° C., also under a neutral atmosphere, in the presence of an inert gas, such as Argon.
• an inert gas such as Argon.
• one or more non-ferrous additives (ANF) intended are introduced (FIG. 6) into the container 10, prior to the preheating step previously described. to lower (in this example at least to 1300 ° C.) the solidification temperature of the liquid catalyst metal which will be poured into this same container 10 during a subsequent step and, on the other hand, to facilitate the separation of the carbon from the metal that contains it.
• NAF non-ferrous additives
• the amount of additive added is of the order of 2 to 3% by volume of the mixture M.
• FIGS. 7 and 8 illustrate the step of filling the container 10 with the mixture M.
• the door 6 of the oven 22 is opened and the sliding bottom 8 is pulled out to remove the preheated container 10 from the enclosure 4 of the oven.
• the container 10 is brought sufficiently outside the oven 22 to clear the opening 16 of this container ( Figure 7). Then, the crucible 1 containing the mixture M in the liquid state is also taken out of the oven 2 and is transported to the container 10. As shown in FIG. 8, the container 10 is filled with the mixture M so as to leave no free space in the container 10, after the hermetic closing operation
• the closing operation is illustrated in FIG. 9.
• the container 10 is closed hermetically using a Morse cone 26 which can be driven into a through upper opening 28, formed in the neck 18 transversely thereto.
• the liquid mixture M is centrifuged rapidly (FIGS. 11 and 12), before it begins to solidify, by first placing the filled and hermetically closed container 10 on the centrifuge device 30. , according to the invention.
• This separation phenomenon is obtained thanks to the fact that the catalyst metal has a density and a mass greater than that of carbon.
• the container 10 and its contents are allowed to cool, if necessary by assisting this cooling by spraying said device with the aid of a coolant until this assembly reaches the temperature. ambient.
• the wall 12, previously expanded to its diameter D3 will retract to resume its initial diameter Dl and thus apply a high and uniform pressure on the catalyst metal in the solidification phase, to the center of the sphere, where there is in particular the carbon N nut which undergoes sufficient pressure for the carbon to recrystallize in the form of a synthetic diamond.
• the container 10 is removed from the centrifuge device 30. Then, as seen in FIG. 13, the solidified mixture is separated from the container 10, by cutting or cutting the container 10, along a radial plane of the container, to release the solidified mixture in the form of a ball B which has in its center the synthetic diamond nut.
• the N nut of synthetic diamond trapped in the solidified catalyst metal is then extracted.
• This extraction step can consist, for example, in heating the ball B to a temperature below its melting temperature to then subject it to a thermal shock (FIG. 15) intended at least to weaken it and / or disintegrate it. at least partially.
• This extraction step can be finalized, if necessary, by applying a mechanical shock to ball B, for example using a simple hammer (figure 16), to burst ball B and recover the nuts N.
• the heating of the ball B can be carried out in an oven of the type of that of FIG. 2, heated in the example shown to a temperature of 800 ° C.
• the thermal shock applied to the ball may consist in particular of quenching in a tank C with cold water EF, during which the catalyst metal splits and cuts partially or completely.
• the device 30 comprises a cage 32 which is intended to receive the container 10, this container being movable in rotation in this cage 32 between a bottom 34 and a cover 36 of the cage 32 intended to cooperate respectively with the guide means and '' rotation drive 20a, 20b and 20c.
• the cover 36 which is articulated in the upper part of the cage 32, has in its central part a recess ent 38 of circular shape provided for receiving, free to rotate, the end of the neck 18 of the container 10, forming said guide means 20a.
• the cover 36 can be blocked on the cage 32.
• the cage 32 includes an extension 40 cooperating with an opening 42 formed in the cover 36, the extension 40 being able to be introduced into the opening 42 in the position closed cover.
• the blocking is achieved by means of a pin 44 driven into a clearance 46 provided for this purpose in the extension 40.
• the container 10 comprises, in its part diametrically opposite the neck 18, the guide and drive means 20b and 20c respectively.
• a cylindrical protuberance 48 preferably coming integrally with the spherical body 14 and extending externally from the spherical body 14 in the extension of the radial axis.
• This protuberance 48 is engaged freely in rotation in a cylindrical clearance 50 provided in the bottom 34 of the cage 32; it forms the rotating guide means 20b.
• This clearance 50 communicates with a passage 52 opening towards the outside of the cage 32.
• the bottom of the cage 32 supports and guides, free in rotation, a drive shaft 54 provided at a first end with a square 56 intended to engage in a recess (not referenced) formed in the protuberance 48.
• the axis 54 has at its second end a pinion with bevel gear 58 meshing with a pinion of the same type 60 driven by another axis 62 mounted also free to rotate in an extension 64 provided in a lower part of the cage 32.
• This second axis 62 extends perpendicularly to the first axis 54 and to the geometric axis of rotation Ri.
• the second axis 62 comprises, on the side opposite to the bevel gear 60, a notched straight gear 66 in engagement with a toothed belt 68 also engaged with another toothed pinion 70.
• the cage 32 is mounted to rotate freely in a frame 72 by means of two pivots 74 and 76 extending from two opposite lateral walls of the cage 32, along a second geometric axis R2 perpendicular to the axis Ri. These two pivots 74 and 76 are supported and guided in rotation inside the frame 72.
• the pivot 76 crosses the toothed pinion 70.
• a drive pulley 80 is driven on the pivot 76 and is driven in rotation by an electric motor 82, via another pulley 84 mounted on a motor shaft 86 of the electric motor 82, the two pulleys 80 and 84 being connected by a toothed belt 88.
• the electrical supply to the motor 82 causes the rotation ROT2 of the cage 32 around the axis R2 and the combined rotation ROTI of the container 10 around the axis Ri.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Inorganic Chemistry (AREA)
• Catalysts (AREA)

Applications Claiming Priority (3)

Publications (1)

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Family Cites Families (6)

• 1997
  • 1997-09-02 WO PCT/CH1997/000322 patent/WO1998009914A1/fr not_active Application Discontinuation
  • 1997-09-02 EP EP97936554A patent/EP0938450A1/de not_active Withdrawn

Non-Patent Citations (1)

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