US3328841A

US3328841A - Flash heating apparatus for diamond synthesis from liquid carbon

Info

Publication number: US3328841A
Application number: US273785A
Authority: US
Inventors: Brayman Jacob
Original assignee: Barogenics Inc
Current assignee: Barogenics Inc
Priority date: 1963-04-17
Filing date: 1963-04-17
Publication date: 1967-07-04
Anticipated expiration: 1984-07-04

Description

' July@ 1961 1. BRAYMAN 3,328,841 FLASH HEATING APPARATUS vFOR DIAMOND l v SYNTHESIS FROM LIQUID CARBON Filed-April 17,l 1963 v l f 2 Sheets- Sheet 1' TEMPERATURE ('K) INVENTOR ancoa BRAYMAN BYM *007;2-1

FLASH HEATING APPARATUS FOR DIAMOND SYNTHESIS FROM LIQUID CARBON Filed April 17,. 1963 2'- Sheers-sneez a mvE'N'ron .mcoe annum A' BY l United States Patent O York Filed Apr. 17, 1963, Ser. No. 273,785 8 Claims. (Cl. 18-16.5)

This invention relates generally -to the synthesis of diamond from soft carbon. More particularly, this invention relates to means for directly converting sort carbon to diamond.

De Carli and Jamieson in an -article (1) entitled Formation of Diamond by Explosive Shock and published in Science (volume 133, No. 3467, pages 1821-1822, June 1961) have described the application to a graphite sample of a shock wave generated by a conventional explosive charge and of an estimated value of 300 kilobars. While the shock wave was observed to produce diamonds, the yield of diamonds was so minute as to be negligible, and the diamonds themselves were of such small size (l0 microns or less in diameter) as to have no practical utility.

More recently, F. P. Bundy in an article (2) entitled Direct Conversion of Graphite to Diamond in Static Pressure Apparatus and published in Science (volume 13'7, No. 3535, pages 1057-1058, Sept. 28, 1962) and in another -article (3) entitled New Phase Transitions in Extended Regions of Pressure and Temperature and publicized at the A.I.M.E. Symposium (Dallas, Tex., Feb. 24- 28, 1963) has disclosed the conversion to diamond of part of a small bar of graphite by the application to that bar of a static pressure of about 130 kilobars and by the flash heating ofthe bar to a temperature of about 3500 K.

Thus, it is now known that soft carbon can vbe converted into diamond directly, i.e., without the intervention of a molten metallic agent for dissolving the carbon.

An object of this invention is to diamondize soft carbon directly by apparatus having advantages over those now known to the prior art..

These and other objects are realized according to the invention by heating a charge including soft carbon to a temperature and under a pressure by which at least some of the carbon is rendered in the stable liquid state. The liquidized carbon is then cooled under pressure conditions which produce resolidication of at least part of the carbon in the form of diamond, and which also, permit recovery ofthe diamondized car-bon.

The charge itself may consist wholly of soft carbon (i.e. graphite or amorphous carbon) or may consist of soft carbon admixed with other substances. Ordinarily, the charge forms one component of a pressure-receiving container of which another component is a casing of pressure transmissible material disposed around the charge. To initiate the method, the container is placed in a press and the press is then actuated to exert on the exterior of the container a static pressure which is communicated through the pressure transmissive material of the casing to the central charge. Conveniently, the press may be of a type which uses tapered pressure-exerting elements or anvils to effect pressure-multiplication. Thus, the press may be, say, of the well known belt type or it may be, say, a cubic or tetrahedral press of the type disclosed in U.S. Patent 2,968,837 issued Jan. 24, 1961 in the name of Zeitlin et al. or, as an alternative example, it may lbe a cylindric-prismatic press of the type disclosed in U.S. Patent 3,080,609 issued on Mar. 12, 1963 in the name of Gerard et al. Where, however, the static pressure employed in the method is relatively low (e.g. on the order of kilobars or less), the press which is used need not necessarily be a pressure-multiplying press.

The charge is heated according to the present method Fice by a ash heating produced by a transient discharge of electric current through the container. An advantage of so ash heating the charge is that the period of heating is so short that the container casing and the press surfaces in cont-act with that casing do not become appreciably heated by conduction or radiation of heat from the charge.

As later described more fully, according to one way of practicing the method the diamondizing of the carbon and the subsequent cooling thereof is promoted by the application to the heated charge of a transient pressure which contributes to the total pressure on the carbon, and which also drives the liquied carbon into forcible contact with the cooler medium provided by the casing to thereby resolidify or freeze the carbon almost instantaneously. Preferably, but not necessarily, the transient pressure is generated by a transient discharge of electric current through the container to produce therein a high energy rate arc discharge through a non-metallic medium or, alternatively, the vaporizing of a metallic medium in the torm of, say, an exploding wire Moreover, pref. erably but not necessarily, the transient pressure is a wavepropagated pressure manifested by a pressure wave which desirably is but need not be a shock wave, i.e., a wave which travels through a medium under given pressure and temperature conditions lat a speed faster than sound.

For a better understanding of the invention, reference is made to the following description of representative methods and means embodying the invention and to the accompanying drawings wherein:

FIG. l is a phase diagram of carbon; and

FIG. 2 is a schematic view in `cross-section of one form of pressing means and pressure-receiving container for the invention.

The diagram of FIG. l is a phase diagram of carbon under various pressure (P) and temperature (T) conditions, pressure being plotted vertically in kilobars and temperature being plotted horizontally in degrees Kelvin. The FIG. 1 diagram is a modified version of a similar phase diagram shown in the aforementioned article (2).

In FIG. 1, the circle 20 at about 130 kb. and 4100 K. is the diamond-graphite-liquid triple point for carbon. The point 20 is connected by a downwardly extending graphite melting line 21 to a graphite-liquid-vapor triple point 22 at about 0.12 kb. and about 4100 K. A line 23 extending rightward from point 22 separates a liquid carbon phase region 24 above that line from a vapor carbon phase region 25 below the line. Note that the graphite melting line 21 extends from triple point 22 'down to zero pressure. This means that at pressures below about 0.12 kb., carbon will sublime from the solid state to the vapor state as the temperature is raised to that required to produce carbon vapor.

Above the triple point 20, the liquid phase region 24 for carbon is to the right-hand side of a diamond melting line 26. The boundary formed by the

lines

21 and 26 is referred to herein as the carbon melting boundary. For all P-T conditions to the left of the carbon melting boundary, carbon is stably in a solid state and can exist as a liquid only in an unusual sense such as by being dissolved in a molten metallic solvent or by pseudomelting. To the right of the carbon melting boundary, carbon is stably in a liquid state.

The area to the left of the carbon melting boundary is divided into P-T regions of interest as follows.

Extending downwardly and leftwardly from triple point 20 is -a line 30 known as the Simon-Berman line. Above line 30 and between that line and line 26 is a P-T region in which diamond is stable. Below the Simon- Berman line 30 and between such line and the graphite melting line 21 is a P-T region in which graphite is stable.

The diamond-stable region above line 30 is further subdivided into an upper region 31 and a lower region 32 by a line 35 extending from triple point 20 and known as the graphite melting line extension. The upper region 31 is an exclusive diamond region in that within that region diamond is stable but graphite cannot persist even in a metastable state for any significant time. Within the lower region 32, diamond is stable and graphite is metastable.

The graphite-stable region below Simon-Berman line 30 is shown in FIG. 1 as being sub-divided by (a) a line 37 from triple point 20 known as the diamond melting line extension, (b) a line 33 referred to herein as the fast graphitizing line. The two last named lines will later be ldiscussed in more detail.

The positions on the FIG. l diagram of the

lines

21 and 30 have been well established by a large amount of experimental work. The position, on the other hand, of the line 35 is based on a lesser `amount of experimental work and on a determination of that position by extrapolation from such Work. Because the position shown in FIG. 1 of the line 35 has so been determined by resort to extrapolation, that position is not necessarily representative of the exact actual bounds of the described

P-T regions

31 and 32 on the opposite sides of line 35. The presence, however, of these regions has been well confirmed by experimental evidence.

In FIG. l, the line 38 is based on experimental results reported in the aforementioned articles (2) and (3). The said line represents the approximate demarcation between a region to the left thereof where no observable graphitizing of diamond occurred within a period on the order of milliseconds and a region to the right thereof where complete graphitizing of diamonds took place within that period. Thus, considering the graphite-stable region bounded by

lines

30 and 21, while in theory it is the line 37 which separates an exclusive graphite region on the right thereof from a stable-graphite metastable-diamond region on the left thereof, as a matter of practice the bound between those leftward and rightward regions can better be considered as represented by the line 38. Such exclusive graphite region rightward of line 38 is designated in FIG. 1 by the reference numeral 42, and it is a region in which graphite is stable but in which diamond cannot persist for any significant length of time in even the metastable state.

Within the region under the Simon-Berman line 30 and to the left of the fast diamondizing line 38, diamond is metastable but has a tendency to graphitize at a rate dependent on the pressure and temperature to which the diamond material is subjected. Qualitatively speaking, that region can be sub-divided into

separate regions

44 and 43 which are respectively disposed leftward and right- Ward of the slow graphitization line 39. The latter line has been plotted on FIG. 1 mostly from experimental data given by F. P. Bundy in an article (4) entitled Diamond- Graphite Equilibrium Line From Growth and Graphitization of Diamond and published in the Journal of Chemical Physics (vol. 35, No. 2, pages 383-391, August 1961).

Within the region 44 bounded by

lines

30 and 39, diamond undergoes no observable graphitizing within a relatively long time period (eg. ten minutes). As the P-T point moves leftwardly from line 39, the graphitizing rate progressively drops off until at atmospheric pressure and room temperature (330 K.) the rate is essentially zero. It is this essentially zero graphitizing rate which accounts for the indefinitely long persistence of diamonds under ordinary conditions.

In the region 43, diamond graphitizes at an appreciable rate which increases in the direction generally indicated by the arrow 45. That is, the graphitizing rate increases with a decrease in pressure or with an increase of temperature or with the -occurrence of both. As indicated previously, in the vicinity of line 39 the graphitizing rate is relatively slow in that it requires a period on the order of minutes or tens of minutes to produce observable graphitization. It is only when `the P-T condition arrives at or near to the fast diamondizing line 38 that the graphitizing rate becomes so fast that observable graphitization takes place within a period on the order of milliseconds.

From the description heretofore given, it is evident that to effect conversion of soft carbon to diamond without intervention of a molten metallic solvent, it is necessary to subject the soft carbon to conditions of pressure and temperature corresponding to a point in the FIG. 1 diagram at which diamondizing takes place. Various exemplary ways of how this is done according to the present invention will now be given.

Referring to FIG. l, the point Y represents atmospheric pressure (one bar) and lroom temerature (about 300 Kelvin). Assuming that a pressure-receiving container with a charge therein comprised of graphite (or another 'form of soft carbon) has been placed in a suitable press, the first step of the method is to actuate the press to apply pressure to the container and the contained charge. According to Example I (a lfirst way of practicing the method), that pressing step develops on the charge a static pressure of about 10l kb. The application of such static pressure is represented in FIG. 1 by an upward movement along the line segment X from the point Y to the point A.

While under such static pressure, the charge is flash heated to a temperature at which the carbon in the charge is brought to a P-T -condition for which carbon is stably a liquid. Such flash heating occurs within a period on the order of from ones to tens of milliseconds, the heating step being represented in FIG. 1 by right- Ward horizontal movement along the static pressure line P1 from the point A to the point B in region 24. Note that, in the course of such movement, the P-T condition of the carbon progresses from the region to the left of line 21 in which carbon is stably solid to the region at the right of line 21 in which carbon is stably of a phase other than solid. Note, moreover, that, because the carbon is under suitable static pressure, the attained P-T point B is above the vapor region 25, wherefore the carbon does not sublime in the course of the crossing of line 21 `by the P-T condition of the carbon. In general, the static pressure applied to the charge during the flash heating should be enough to maintain the end point B above line 23 which separates the liquid region 24 from the vapor region 25. Otherwise, the value of static pres- Sure -used is discretionary.

The charge is heated so rapidly by the flash heating that the casing material around the charge has no opportunity to become appreciably heated by conduction or radiation of heat from the charge. Therefore, at the end of the ash heating step, the bulk of the casing material is much cooler than the charge material.

As described, the flash heating produces a liquication of the carbon in the charge. Thereafter, but before the car-bon has had an opportunity to undergo any appreciable cooling, the charge is subjected to a high-magnitude transient pressure which is preferably a wave-propagated pressure generated by a shock wave. A first effect of the shock wave on the charge is to greatly increase for an instant the total pressure on the charge. That increase in total pressure is represented in FIG. 1 -by upward movement from point B along the line M to the point C. As shown, point C has a pressure value well above the pressure characterizing the graphite-diamond-liquid triple point 20.

A second effect of the shock wave is to produce rapid cooling of the liquid carbon yby -fragmentizing the charge so as to drive the carbon in the form of molten droplets into the adjacent cooler casing material. When the molten carbon droplets are so forced into contact with the much cooler medium provided by the casing, the `droplets freeze almost instantaneously by virtue of loss of heat to the medium. Such freezing takes place so rapidly that aaaasiti it occurs while the carbon is still being subjected to the transient pressure developed by the shock wave. Therefore, the cooling step is suitably represented in FIG. 1 by leftward movement of the P-T condition of the carbon from Ipoint C along line N to the point D.

In the course of such leftward movement, the P-T condition of the carbon leaves the liquid region 24 and passes into region 31 within which the carbon resolidifes. As stated, the region 31 is an exclusive diamond region in that, while the diamond form of carbon is stable therein, the graphite form of carbon cannot persist therein even metastably. Accordingly, the carbon resolidifies in diamondized form.

Further leftward movement in FIG. 1 of the P-T condition of the cooling carbon brings that condition into the region 32 in which diamond is stable and graphite is metastable. In this latter region, no graphitizing occurs of the obtained diamond material, and, accordingly, the diamondized material is preserved for later recovery.

As the carbon cools, the transient pressure from the shock wave dissipates to thereby produce a fall in the total pressure on the carbon. That drop in total pressure is represented in FIG. 1 partly by the downward inclination from right to left of the line N and partly by the line L extending downward from point D. The subsidence of -both the cooling effect and the transient pressure effect of the shock wave renders the carbon in a P-T condition represented in FIG. 1 by the point E. Thereafter, the carbon cools in a manner represented by leftward movement in FIG. 1 from point E along line P1 back to the point A. Because the carbon was initially heated by flash heating, the cooling along line P1 takes place rapidly. Therefore, even though point E is in region 43 within which diamond graphitizes, t-he time period which elapses before the P-T condition of the carbon crosses line 39 is so short that there is no appreciable graphitizing in that period of the diamondized carbon. Once, of course, that the 'P-T` condition of the carbon crosses line 39 to enter the region 44 and thereafter a-ttain the point A, the graphitizing rate of the diamondized carbon is negligible.

The method is completed by removing the static pressure exerted on the container (the corresponding movement in CE-IG. 1 being from point A down along line segment X to point Y). Thereafter, the container is opened to recover therefrom the yield of diamond Inaterial.

In FIG. 1, the .lines M, N and L Aare to be taken more as qualitatively illustrating the pressure and temperature variation caused by the shock wave than as accurately indicating in a quantatative sense the transient P-T variation. The reason why those lines should so be considered is that there is no reliable means for measuring accurately the instantaneous pressure and temperature values caused by the shock wave.

The method may also be practiced in a way which is referred to herein as Example II, and which does not require the generation of a sho-ck wave. According to Example II, the container and the charge therein are first subjected by carbide pressure-mul-tiply-ing anvils to a static pressure which is above that characterizing the graphite-diamon-d-liquid triple point. The static pressure application 4is represented in FIG. 1 -by upward movement from point Y along line segments X and X to point A. Preferably, the static pressure is on the order of about 150 -kilobars since such Va pressure value can be exerted by carbide anvils without breakage thereof over a number of compressing cycles.

Next, while the full static pressure is maintained, the charge is flash heated as before to liquify the carbon by bringing the P-T condition thereof into the region 24 within which carbon is stably a liquid. This heating step is represented in FIG. 1 by rightward movement from point A along the horizontal static-pressure line P2 to the point B. As in the case of point B, the pressure value 6 characterizing point B is `sufficient lto preclude Vaporizing of the carbon at -the highest temperature attained thereby.

After the car-bon in the charge has been liquied by the 'flash heating, the charge is simply allowed to cool while full static pressure is maintained thereon. The cooling step is, therefore, -represented in FIG. 1 by a movement from point B' back along the static pressure line P2 to the point A. During this leftward movement, the P-T condition of the carbon leaves the liquid region 24 by passing as before into the region 31 within which carbon resolidies in the form of diamonds. Thus, diamondizing of the carbon takes pl-ace. Further cooling brings the P-T condition into region 32 `and back to point A' therein. The entire region 32 is, however, a P-T region in which diamond does not graphitize. Hence, in the course of cooling to the condition represented by point A', there is no loss of the diamond material obtained by the initial resolidioation of the carbon in region 31.

The `final step of the method accord-ing to Example II is, of course, to remove the static pressure from the container (the corresponding movement in FIG. 1 being from point A down along line segments X and X back to point Y). `Because in such movement, the P-T condition of the carbon passes directly from the non-graphitizing region 32 to the region 44 within which the graphitizing rate is negligible, no loss of diamond material is occasioned by the static pressure removal. As before, when the point Y is reached, the container is opened and the yield of diamond material is recovered.

In the method accord-ing to Example I-I, the maintenance of full static pressure during the cooling of the carbon serves alone to cause -the P-T condition of the carbon to follow a path in FIG. 1 which is well displaced from those P-T regions within which diamond .graphitizes In other words, Example II contrasts with Example -I in that, in the method as practiced according to Example II, 4graphitization is avoided irrespective of the rate at which the carbon cools. Therefore, in Example II, the rate need only be sufficiently rapid to avoid overheating of the anvils. It is desirable to use as slow a cooling rate .as will satisfy the last name-d requirement in order thereby to increase the particle size of the diamonds produced upon resolidication of the carbon. The cooling rate may, of course, be slowed down by increasing the time period over which the charge is heated whether by a transient discharge of current or by, say, a short application of steady state current.

Reference is now made to FIG. 2 which illustra-tes apparatus for carrying out the method according to Example I. In FIG. 2, a cubic pressure-receiving container 50 is shown as being contacted by pressure-multiplying anvils 51-54 of cemented carbide. The yanvils 51-54 form four of a set of six identical anvils hav-ing respective front faces of which each contacts a respective one of the six outside faces of container 50i. Those six anvils are components of a cubic pressure-multiplying press such as, say, a cubic press of the sort disclosed .in U.S. Patent 2,968,837 issued on Jan. 24, 19611 in the name of Zeitlin et al. Each .anvil front face is square and is 1.74" on a side, whereas the cubic container 50 is 3" on a side. Because each anvil face is smaller than the face contacted thereby of the container, the various anvils are separated from each other by inter-anvil gaps 59.

To provide for more effective -compression of container 50, the edges and vertices thereof may he reinforced by exible sheet coverings in the manner taught in co-pending `application S.N. 240,049 filed Nov. 26, 1962 in the r name of Brayman et al. and owned Iby the assignee of this is a 11/2" long, cylindrical mandrel 65 of silver chloride. As `taught in co-pending application S.N. 240,691 filed Nov. Z8, 1962 in the name of Zeitlin et al. and owned by the assignee of this application, now Patent No. 3,175,068, the mandrel has formed on its cylindrical surface a helical groove 66 which progresses axially from one end of the mandrel to the other. Within this groove is seated a continuous graphite wire 67 of 0.052 diameter. The graphite wire 67 may be fabricated by depositing a graphite paste in groove 66 and then allowing the paste to harden. As is evident, the wire 67 provides for the method the charge of soft carbon.

The wire 67 is contacted at opposite ends of mandrel 65 by a pair of 1A diameter copper conductor rods 71 and 72 at right angles to the mandrel axis and extending outwardly from wire 67 through, respectively, the upper block 61 and the lower block 62. The outer end of rod '71 is flush with the upper outside face of block 61 and is in electrical contact with the front face of anvil 51. Analogously, the outer end of rod 72 is flush with the lower outside face of block 62 and is in electrical contact with the fro-nt face of anvil 52.

The mandrel 65 has therein a central axial bore containing a 0.020 diameter (approximately) Nichrome exploding wire 75 -contacted at opposite ends by a pair of metal tabs 66, 67 lying flat against the opposite ends of the mandrel. The. tabs 66 and 67 are, in turn, respectively contacted by the inward ends of a pair of 1A" diameter, copper electrode plugs 78 and 79 extending axially in the mentioned bore in opposite directions away from the mandrel. The plugs are held in position within Vthe bore by two pyrophyllite sleeves `80 and 81 of which each surrounds a respective one of the plugs. As shown, the outer end of plug 78 makes electrical contact through a metal tab -82 with the left hand horizontal anvil 53, whereas the outer end of plug 79 makes contact through a metal ta-b 83 with the front face of the right-hand horizontal -anvil 54.

The Vertical anvils 51 and 52 are connected in a flash heating circuit of which other components are a switch S1 and a schematically 4represented capacitor storage bank 85 chargeable through the

terminals

86 and 87. The horizontal anvils are likewise connected in an electrical circuit, namely an exploding wire circuit of which `other components are a switch S2 and a schematically represented capacitor storage bank 90 chargeable through the

terminals

91 and 92. P-referably, the two circuits are electrically isolated from each other to the extent that each circuit offers a very high impedance to current flowing in the other. If desired, an auxiliary spark gap (not shown) may be incorporated for current control purposes in each circuit `between the capacitor bank thereof and one of the anvils connected in such circuit. In each circuit, the capacitor storage bank has an energy storage capacity of about 60,000 joules.

The switches S1 and S2 of the two circuits are each of the trigatron type or of the `thyratron type. Each of the switches is closed by a separate trigger signal from a common electronic timer T which causes-a closure of S2 `a predetermined time interval after the closure of S1. Devices suitable for use as timer T are well known in the electronic art. For a teaching on capacitor banks providing a large energy storage and on circuits suitable for the large transient discharge currents produced by such banks, reference is made to the text Exploding Wires edited by W. G. Chase and H. K. Moore (Plenum Press, New York, 1959).

The FIG. 2 apparat-us operates as follows to carry out the method according to Example I. First, the anvils which surround container 50 are simultaneously actuated to exert pressure on the container. Under this anvil pressure, the pyrohyllite around the edges of the container tends to flow into the inter-anvil gaps 59 to there form autogenous gaskets in a manner wel-l-known to the art. The same anvil pressure develops in the central part of the container a hydrostatic pressure which is communicated as a pressure of about l0 kb. to the graphite wire or charge 67.

Once the Igraphite charge is under static pressure, the timer T is actuated to send to switch S1 a trigger signal Serving to close the switch. Upon the closure of the switch S1, the previously changed capacitor bank produces a transient discharge of current at a high energy rate through the helical graphite wire 67 by way of the

anvils

51, 52 and the rods 71 and 72. The discharge current through graphite wire 67 produces the flash heating and liqui-fication of lthe graphite which has been previously described.

Because the graphite wire 67 is flash heated, the temperature of the wire reaches its peak (represented by point B in FIG. 1) within `a period on the order of ones or tens of milliseconds from the closure of switch S1. After a time delay approximating this period (i.e., before the graphite wire has had an opportunity to cool appreciably and, also, before the pyrophyllite in the blocks 71 and 72 has had time to heat appreciably), the timer T sends out a second trigger signal, this time to the switch S2 to produce closure of :the last-named switch. When switch S2 so closes, the previously charged capacitor bank produces a transient discharge of current at a high energy rate through the exploding wire 75 by way of the anvils 53, 541- and by way of the electrode plugs 78, 79 (and associated metal tabs). In response to this transient discharge of current therethrough, the wire 75 vaporizes and explodes to generate the previously described shock wave.

The shock wave serves (as earlier described) both to develop a transient pressure on the now liquied carbon and to fragmentize the mandrel 65 land the liquid charge of carbon. The shock wave furthermore drives droplets of liquid carbon from the fragmentized charge into forcible contact with the cooler pyrophyllite surounding the charge to thereby produce the described almost instantaneous freezing in the form of diamond material of the previously liquid carbon.

Upon sufficient cooling of the carbon, the anvils are retrac-ted from the container to receive the static pressure thereon and to permit removal of the container from the press. The anvil retraction operation completes the carrying out of the method insofar as the FIG. 2 apparatus is concerned.

While the foregoing has been a description of the use of the FIG. 2 apparatus in practicing the method according to Example l, it will be appreciated that the same apparatus may be employed in connection with the practice of the method according to Example II. When, however, the method is practiced according to the latter example, the exploding wire 75 and the circuit and circuit cornponents associated therewith are omitted, the timer T may also be omitted (i.e., switch S1 can in this instance be a conventional switch), and the anvils are actuated to exert on the graphite charge 67 a pressure of about 150 kilobars in contrast to the pressure of about 10 kb. exerted on the charge during the practice of the method according to Example I.

`The above described methods and means being exemplary only, it will be understood that additions thereto, omissions therefrom and modifications thereof can be made without departing from the invention, and that the invention comprehends embodiments differing in form and/or detail from those specifically disclosed. For example, in lieu of using rod conductor 72 (FIG. 2), the graphite wire 67 may be extended leftward to connect with the copper plug '78, and the flash heating circuit may be connected between the

anvils

51 and 53 to thereby use the latter anvil as a common anvil for both the flash heating circuit and the exploding wire circuit. In this manner one of the terminals on the outside of container 50 may be eliminated while, at the same time, the currents in the two circuits are maintained independent in the sense that neither circuit acts as a by-pass for current in the other circuit.

Accordingly, the invention is not to be considered as limited save as is consonant with the recitals of the following claims.

I claim:

1. A pressure receiving container comprising, a charge in said container, a casing of pressure-transmissive material disposed around said charge and providing the exterior of said container, means in said container .and responsive to electric current to exert a transient pressure on said charge, a plurality of at least three current terminals disposed at separate locations on the exterior of said container, means defining between a rst pair of said terminals a path through said container for heating current for said charge, and means defining between a second pair of said terminals a path through said container for current for said pressure-exerting means, said second pair of terminals excluding at least one of the terminals in said rst pair thereof.

2. A container as in claim 1 in which said first pair of terminals is comprised of two terminals disposed on first opposite sides of said container, andv said second pair of terminals is comprised of another two terminals disposed on second opposite sides of said container.

3. A container as in claim 2 in which said first opposite sides are at right angles to said second opposite sides.

4. Apparatus comprising, a pressure-receiving container, a charge in said container, a casing of pressure-transmissive material disposed around said charge and providing the exterior of said casing, a plurality of pressure-multiplying anvils disposed around said container to be separated by inter-anvil gaps and to operably compress said container along center lines of actions lying in dilierent planes, means including a first pair of terminals each on the outside of said container and electrically coupled with a respective one of a iirst pair of said anvils to provide a first path through said container for electric current, and means including a second pair of terminals each on the outside of said container and electrically coupled with a respective one of a second pair of said anvils to provide a second path through said container for electric current, said second pair of terminals and said second pair of anvils excluding, respectively, at least one terminal in said rst pair thereof and at least one anvil in said second pair thereof.

5. Apparatus comprising, a plurality of pressure multiplying anvils disposed in different planes around a central space to compress an object therein, a first electric circuit connected to a rst pair of said anvils to pass electric curv rent therethrough and through said object when the latter is in said space vand is contacted by such pair of anvils, and a second electric circuit connected to a second pair of said anvils to pass electric current therethrough and through said object when such object is in said space and is contacted by said last-named anvils, said second pair of anvils excluding at least one of the anvils in said first pair thereof.

6. Apparatus comprising, a pressure-receiving container having a charge therein, a first circuit coupled with said container to pass therethrough a first transient discharge of electric current, a second circuit coupled with said container to pass therethrough `a second transient discharge of electric current, and electronic timer means coupled to both circuits to control the relative timing of said two discharges so as to initiate said second discharge a predetermined time interval after the initiation of said iirst discharge.

7. Apparatus comprising, a pressure receiving container having a charge therein, iirst and second current sources, a iirst circuit for flow of current from said tirst source through said container, and a second circuit for iiow of current from said second source through said container, each of said circuits offering a high impedance to flow therein of current produced in said container by the current source in the other circuit.

8. Apparatus as in claim 7 in which said rst circuit includes a first pair of pressure multiplying anvils disposed around said container to compress it and a first pair of terminals disposed on the outside of said container to each be electrically coupled with a respective one of said first anvils, and in which said second circuit includes a second pair of pressure multiplying anvils disposed around said container at different positions than said rst anvils to compress said container and a second pair of terminals disposed on the outside of said container to each be electrically coupled with a respective arc of said second anvils.

References Cited

Claims

6. APPARATUS COMPRISING, A PRESSURE-RECEIVING CONTAINER HAVING A CHARGE THEREIN, A FRIST CIRCUIT COUPLED WITH SAID CONTAINER TO PASS THERETHROUGH A FIRST TRANSIENT DISCHARGE OF ELECTRIC CURRENT, A SECOND CIRCUIT COUPLED WITH SAID CONTAINER TO PASS THERETHROUGH A SECOND TRANSIENT DISCHARGE OF ELECTRIC CURRENT, AND ELECTRONIC TIMER MEANS COUPLED TO BOTH CIRCUITS TO CONTROL THE RELATIVE TIMING OF SAID TWO DISCHARGES SO AS TO INITIATE SAID SECOND DISCHARGE A PREDE-