IE43344B1 - Improvements in process for the manufacture of diamond proucts and apparatus therefor - Google Patents

Description

This application relates to an improved process for growing diamonds on diamosd seeds and improvements in an apparatus therefor.

Background of the Invention - The synthesis of diamond crystals by high pressure, high temperature processes is well known. Preferred methods for making diamonds are disclosed and claimed in Hall et al, U.S. 2,947,610, and in Strong, U.S. 2,947,609. Apparatus for carrying out such processes is described and claimed in Hall, U.S. 2,941,248.

Diamond growth in the aforementioned processes occurs by the diffusion of carbon through a thin metallic film of any of a series of specific catalyst-solvent materials. Although such processes are very successfully employed for the commercial production of industrial diamonds, the ultimate crystal, size of such diamond growth is limited by the fact that the carbon flux across the catalyst film Is established by the solubility difference between graphite (the typical starting material) and the diamond being formed. This solubility difference is generally susceptible to significant decrease over any extended period due to a decrease in pressure in the system and/or poisoning effects in the graphite being converted.

On the other hand, in the method of growing diamond on a diamond seed crystal disclosed in Wentorf, Jr., U.S. 3,297,407, a difference in temperature between the diamond seed and the source of carbon, is relied upon to establish a concentration gradient in carbon for deposition on the seed. Catalyst-solvents disclosed in the aforementioned Hall et al and Strong patents are used in the -243344 temperature gradient method of Wentorf, Jr,, as well. The growth of diamond on the seed material is driven by the difference in solubility of -343344 diamond in the molten catalyst-solvent metal at the nutrient (source of carbon) and at the seed, between which locations a temperature gradient exists. Most importantly, this general type of reaction vessel configuration presents a pressure stable system so that pressure can more readily be kept in the diamond stable region.

By very carefully adjusting pressure and temperature and utilizing relatively small temperature gradients with extended growth times (relative to growth times for thin film method), larger diamonds can be produced by the method as taught in the Mentorf, Jr. patent than by the thin-film method.

However, until now, attempts to produce reliably very high quality diamond growth have presented a number of apparently mutually exclusive, yet simultaneously occurring problems.

The major problems are (i) a strong tendency toward spontaneous nucleation; (ii) a tendency for the diamond seed material to dissolve too soon; and (iii) lack of ability to control and produce gem-quality coloration and patterns in the diamond products.

I Spontaneous nucleation of diamond crystals near the diamond seed material (which occurs with increase in the temperature gradient over the safe value) is bad because, •if the growth period is extended to produce diamond growth from the seed of greater than about 1/20 carat in size, the nucleated growth competes with the growth from the diamond seed with subsequently occurring collisions of multiple crystals that result in stress fractures therein.

Partial or complete dissolution of the diamond seed material in the melted catalyst-solvent metal is bad if it occurs at the wrong time because dissolution of the seed produces uncoordinated diamond growth proceeding from spaced loci, and such growths upon meeting, result in subsequent confused, flaw-filled products.

Lack of ability to exercise reproducible control over the diamond growth process is bad because it is not possible to use dopants, getters, compensators, and the like, to produce diamond products having unique color patterns, flaw-free characteristics and optimum physical properties.

The preparation of large size diamonds- by the enlargement in stages of a small diamond has been proposed in the past.

By such a process, a small diamond is placed in a mass of graphite-catalyst mix (thin film method) and new diamond growth is deposited thereon to the extent possible. This enlarged crystal is then re-introduced into the apparatus for further enlargement, as desired. This sequential onion-skin growth has the disadvantage that occlusions of impurities are always introduced at the interface between the old growth and the new layer. Also, if layers of different colors of diamond growth be used, a sharp demarcation, or boundary, will be created between the successive layers.

It would be preferable to avoid occlusions and provide diffuse boundaries between colors. Such a diamond crystal requires a continuous growth during which the desired colorations are controllably introduced. It is an object of this invention to use barrier layers to accomplish this. -514 Accordingly, the present invention provides a process for the production of diamond material comprising the steps of: pressurizing a reaction vessel containing a diamond seed material and a material comprising a source of carbon or a source of carbon containing an impurity for coloring diamond growth, separated by a mass of material comprising a catalyst-solvent or a catalyst-solvent containing an impurity for coloring diamond growth, to a pressure in the diamond stable region of the phase diagram for carbon; while simultaneously heating said reaction vessel in such a manner that the diamond seed material is at a temperature near the minimum temperature of said region and said source of carbon is at a temperature near the maximum temperature of said region, whereby a temperature gradient is created between said seed material and carbon source; characterized by inhibiting diamond growth in at least one of the following group of locations (a) on the diamond seed material until the catalyst-solvent material is saturated with carbon (b) in the vicinity of the diamond seed material and (c) a combination of such locations, under the operating conditions until a substantial diamond growth pattern has been developed from said seed material .

The present invention also provides an apparatus for the production of diamond material comprising a reaction iS vessel containing a diamond seed material and a material comprising of a source of carbon or a source of carbon containing an impurity for. coloring diamond growth separated by a mass of material comprising a catalyst-solvent or a catalystsolvent containing an impurity for coloring diamond growth; means for pressurizing said vessel to a pressure in the diamond stable region of the phase diagram for carbon; means for heating said vessel, contemporaneously with pressurization, in such a manner that the diamond seed material is at a temperature near -13 3 4 4 the minimum temperature of said region and said source of carbon is at a temperature near the maximum temperature of said region, whereby a temperature gradient is created between said seed material and carbon source; characterized by means interposed between said diamond seed material and catalyst solvent for inhibiting reaction of the catalyst solvent with said seed material and in the peripheral vicinity thereof, under the operating conditions of the diamond making process until a substantial diamond growth pattern has developed from said seed material.

Thus large, high quality diamond products are obtained in high temperature, high pressure processes employing a source of carbon on one side of a mass of catalyst-solvent and a diamond seed material on the other side, and maintaining a temperature differential between the carbon source and the diamond seed, if one or more barrier layers for suppressing nucleation and dissolution of the diamond seed are interposed between the mass of catalyst-solvent and the seed. Predetermined colors and patterns are produced in gem quality products of the process by including dopants, colorants and compensators in the source of carbon and/or the catalyst-solvent.

The inhibition of diamond growth can be affected by means which allows the isolation of the seed material from the catalyst solvent until the catalyst solvent is saturated with carbon so that erosion of the seed material can be prevented. The seed material, carbon source and catalyst solvent can also be arranged in the reactor vessel in a stacked planar relationship with one another. The isolation layer can also be separated from the mass of catalyst-solvent by the nucleation suppressing layer. The nucleation suppressing layer may melt at a temperature higher than the mass of the catalyst-solvent and is a material different from said mass.

The present invention will be further described by way of example only, with reference to the accompanying drawings in which:4 3 3 4-1 FIG. 1 illustrates one exemplary high pressure, high temperature apparatus useful in the present invention; FIG. 2 illustrates in an enlarged vertical cross-section of a reaction vessel construction assembly in accordance with a first embodiment of this invention in which a nucleation barrier having an opening is used; FIG. 3 is an even larger scale view of the vicinity of the diamond seed material shown in Fig. 2; FIG. 4 shows the relation between the new . diamond growth and the diamond seed in the embodiment of Fig. 2; FIG. 5 illustrates an enlarged vertical crosssection of another reaction vessel construction assembled in accordance with a second embodiment of this invention in which an extension of the catalyst-solvent is made to interconnect with the diamond seed material through the nucleation !0 barrier; - 8 433 1 Fig. 6 is an even larger scale view of the vicinity of the diamond seed material shown in Fig. 5; Fig. 7 is an enlarged vertical cross-section of another reaction vessel construction in accordance with a third embodiment of this invention, in which a nucleation barrier is provided with restricted growth paths for the diamond product Fig. 8 is an even larger scale view of the vicinity of diamond growth paths according to the aspect of the invention illustrated in Fig. 7; Fig. 9 is a view similar to Fig. 8 showing diamond growth paths as openings without wires therein in accordance with an embodiment broadly shown in Fig. 7; Fig.· 10 is an enlarged vertical cross-section of reaction vessel construction assembled in accordance with a fourth embodiment of this invention, in which an isolation barrier is used to prevent premature melting of the diamond seed; Fig. 11 is an even larger scale view of the vicinity of the diamond seed material shown in Fig. 10; Figs. 12, 13, 14, 15 and 16 are large scale views of the vicinity of the diamond seed material as this region would appear in several variations of the construction shown in Fig. 10; Fig. 17 ’shows the relation between new diamond growth, the diamond seed material, and the calalyst-solvent bath in the embodiments described in Figs. 10-16; Fig. 18 illustrates an enlarged vertical crosssection of a basic vessel configuration for containing various charge assembly embodiments to accomplish coloration and/or pattern formation in a single growth step according to a fifth embodiment of this invention; - 9 433 ί 4 Fig. 19 is a large scale view of a vessel construction for use in the embodiment of Fig. 18, for the preparation of star gem diamonds; and Figs. 20, 21 and 22 are larger scale views of a 5 series of charge assembly embodiments for containment in a reaction vessel construction such as is shown in Fig. 18, in which colored zones and/or patterns are produced in accordance with this invention. 433 14 Description of the Invention INTRODUCTION The present invention relates to a process and apparatus tor producing diamonds of gem size quality. To provide an understanding of the overall approach a brief introduction outlining the basic approach will be presented prior to the detailed description of the various aspects of the invention. The basic approach is to subject a reactor vessel containing a diamond synthesis mixture to pressure and temperature in the diamond stable region of the carbon phase diagram. The synthesis mixture includes a diamond seed material and a source of carbon separated by a mass of catalyst solvent. These elements are positioned in layered or stacked relationship as discussed but other arrangements are also possible. The heating of the reactor vessel is controlled to provide a temperature gradient within the mixture so that the diamond seed material is at a temperature near the minimum value of the diamond stable region and the carbon source is at a temperature near the maximum value.

Now, by inhibiting the reaction of the catalyst solvent at the site of the seed material and in its vicinity until substantial diamond growth has been developed spontaneous nucleation and seed erosion, which militate against growth of gem sized diamonds, are minimized. This result is achieved by interposing suppression or isolation layers or both between the catalystsolvent and the seed material.

In addition to inhibiting catalyst-solvent reaction, controlled amounts of dopants, getters, compensators, mixtures thereof, may be added to the mixture for the manufacture of reliably reproducible diamond crystal products having predetermined coloration, color patterns or zoned coloration.

Preferably, the barrier layer or layers i.e. the nucleation suppressing layer and the isolation barrier and the mass of catalyst-solvent will be of different materials in any given reaction vessel construction.

Preferably, a nucleation suppressing layer will be constructed of cobalt, iron, manganese, titanium, chromium, tungsten, vanadium, niobium, tantalum, zirconium, alloys of the preceding metals, natural mica, polycrystalline, high density alumina, powdered alumina, quartz, silica glass, hexagonal boron nitride crystals, cubic boron nitride crystals, wurtzite structure boron nitride crystals or silicon carbide protected with one of the metals of the platinum family.

Preferably, an isolation barrier will be constructed of a material different from that of a nucleation suppressing layer, if used, and selected from platinum, molybdenum, titanium, tantalum, tungsten, iridium, osmium, rhodium, palladium, vanadium, ruthenium, chromium, hafnium, rhenium, niobium, zirconium, and alloys thereof.

The carbon source and catalyst-solvent mixtures will be any material conventionally used for this purpose and abundantly illustrated in the said Wentorf, Jr. patent. Preferred such materials will be illustrated hereinafter. 433 14 In the context of this have the meanings set forth: a) dopant: b) getter: c) compensator: invention, the following words an impurity which if present at the site of growing diamond will enter the growing diamond lattice and influence the physical, mechanical and/or electrical properties of the diamond growth; a material, the atoms of which, if present at the site of growing diamond, will prevent or limit the entry of one or more dopant materials into the developing diamond growth; and A material, the atoms of which, if present at the site of growing diamond, will enter the growing diamond lattice and partially or completely offset the usual influence of one or more dopant materials present in the lattice with respect to physical, mechanical and/or electrical properties of the diamond.

Such materials are well known to those of ordinary skill in this art. Many will be illustrated hereinafter. Blue-white gems, for example, are produced if boron alone, or especially combined with aluminum, are added as dopants. Conveniently, the aluminum can be alloyed with the catalyst-solvent. Multiple layers of nutrient material and catalyst-solvent may, of course, be used, each containing one or more dopants, getters, or compensators, to produce desired effects, as will be illustrated hereinafter. For example, in one embodiment, aluminum, titanium, zirconium, or an alloy thereof can be in one layer and nitrogen, boron or sources of these, can be in another. If the diffusion paths for each are of different lengths, then color zones can be conveniently produced in the final diamond product.

Preferably, the diamond seed material will be a single crystal. Especially preferably, a cube face of the crystal will be oriented in contact with the barrier layer or the mass of metallic catalyst-solvent. In other preferred features, the diamond seed material can also consist of single crystals at spaced locations.

REACTION VESSEL Common to all apsects, one preferred form of a high pressure, high temperature apparatus in which the process and the improved reaction vessel of the instant invention may be employed is the subject of the aforementioned Hall patent, 20 U.S. 2,941,248, and is schematically illustrated in Fig, 1, In Fig. 1, apparatus 10 includes a pair of cemented tungsten carbide punches 11 and 11' and an intermediate belt or die member 12 of the same material. Die member 12 defines s centrally-located aperture and in combination with punches 11, 1Γ defines two annular volumes. Between punch 11 and the die 12 and between punch 1Γ and the die 12 there are included gasket/insulating assemblies 13, 13’, each comprise 3 3 14 a pair of thermally insulating and electrically non-conducting pyrophyllite members 14 and 16 and an intermediate metallic gasket 17. Each punch carries an end cap assembly which includes a pyrophyllite plug, or disc, 23 surrounded by an electrical conducting ring 24. The aforementioned assemblies 13, 13', together with end cap assemblies 19, 19' and electrically conductive metal end discs 21, 21’, serve to define the volume 22 occupied by reaction vessel 30.

NUCLEATION SUPPRESSION LO In a first preferred embodiment, the process and apparatus of this invention will employ a nucleation barrier layer having at least one opening therein. Referring to Fig. 2, reaction vessel 30 is of the general type disclosed in Strong, U;S. 3,030,662, (incorporated by reference) modified by the addition .5 of steel retaining rings 31 and 32.

Vessel 30 includes an outer hollow cylinder 33 which is preferably made of pure sodium chloride, but may be made of other material such as talc. Broad criteria for the selection of the material for cylinder 33 are that the material a) not be con° verted under pressure to a stronger and stiffer state as by phase transformation and/or compaction and b) be substantially free of volume discontinuities appearing under the application of high temperature and pressures, as occurs for example with pyrophyllite and porous alumina. The materials meeting the criteria set forth in U.S. 3,030,662 (Column 1, line 59 through Column 2, line 2), incorporated herein by reference, are useful for preparing cylinder 33. Positioned concentrically within and adjacent cylinder 33 is a graphite electrical resistance heater tube 34. When reaction vessel 30 is disposed in space 22, heater tube 34 forms electrical contact between end discs 21, 21' so that heat may be controllably applied during conduct of the process. Within graphite heater tube 34 there is in turn concentrically positioned cylindrical salt liner plug 36 upon which are positioned hollow salt cylinder 37 and its contents.

Operational techniques for applying both high pressures and high temperatures in this apparatus are well known to those 10 skilled in the art. The foregoing description relates to merely one high pressure, high temperature apparatus. Various other apparatuses are capable of providing the required pressures and temperatures that may be employed within the scope of this invention. Pressures, temperatures, metallic catalyst-solvents and calibrating techniques are disclosed in the aforementioned patents incorporated by reference.

In Fig. 2, the bottom of cylinder 37 encloses embedment disc 38 having at least one diamond seed 39 embedded therein. Designations of the diamond seed are schematic. As shown, seed 39 is located in a portion of disc 38 projecting from surface 40 thereof a sufficient distance to present the exposed face of seed 39 through hole 41 in nucleation suppressing layer 42 made up of a layer of particulate material or a solid disc.

Hole 41 is filled with the seed presenting the exposed upper surface of diamond seed material 39 (preferably a cube fac$ into contact with the undersurface of plug 43 of metallic catalyst-solvent (Fig. 3). The thickness of plug 43 helps determine the temperature difference prevailing in the cell. - 17 3344 .0 With a thicker plug, the temperature difference is greater.

Also located within salt cylinder 37 are the nutrient supply 44 and salt cylinder 46 disposed thereover. The nutrient material 44 is the source of carbon and may he composed of diamond, diamond plus graphite or may he entirely of graphite, if desired. When mixed with diamond the graphite occupies any void space. It is preferred that the nutrient contain mostly diamond in order to reduce the volume shrinkage that can result during conduct of the process. In conduct of the process any graphite present at operating temperatures and pressures converts to diamond before going into solution in the catalyst-solvent metal. Thus, the pressure loss due to volume change of graphite changing to diamond is minimized so that the overall pressure remains in the diamondstable region at the operating temperature. The vertical dimension of plug 43 also affects the temperature gradient.

Pressure-transmitting members 36, 37, 38 and 46 are made of material meeting the same criteria as the material for cylinder 33. All of parts 33, 36, 37, 38 and 46 are dried in vacuum for at least 24 hours at 100 to 200°C., e.g., 124°C., before assembly. Other combinations of shapes for the pressuretransmitting members 36, 37, 38 and 46 may, of course, be employed. However, the arrangement of these parts shown in Fig. 2 has been found to be the most convenient to prepare and assemble. For example, it may be simpler to make cylinder 37 just long enough to enclose elements 38, 42, 43 and 44 in which case element 44 will be made with a large enough diameter to fit closely within heater tube 34.

Nucleation suppressing layer 42 Is composed of a material different from the catalyst-solvent employed and selected from the group consisting of cobalt, iron, manganese, titanium, chromium, tungsten, vanadium, niobium, tantalum, zirconium, alloys of the preceding metals, natural mica, polycrystalline high-density alumina, powdered alumina, quartz, silica glass, hexagonal boron nitride crystals, cubic boron nitride crystals, wurtzite-structure boron nitride crystals and silicon carbide protected with one of the metals of the platinum family. Silicon carbide particles are preferably mixed with an inert material, such as, sodium chloride and formed as a solid disc having the upper surface thereof (in contact with the underside of plug 43)covered with a thin layer of one of the platinum family metals. The thickness IB of the nucleation suppressing layer 42, would range from about 1 to about 10 mils. The natural mica, e.g., muscovite should first be fired at about 800°C. for 12-15 hours. The preferred thickness of mica is about 2-3 mils.

Enough of the surface of the underside of catalyst20 solvent metal plug 43 is covered by layer 42 to provide an environment adjacent the seed 39 to suppress spontaneous diamond nucleation for a considerable distance around diamond seed 39. Preferably, the entire underside of plug 43 is covered by layer 42, but if less than the entire surface is covered, the layer 42 should extend at least 50% greater distance In all directions from the seed than the lateral growth 14 dimension desired for the diamond. If the layer 42 is made of one of the metallic materials listed above, some space must exi st between the diamond seed 39 and the wall of hole 41 into which the material of disc 38 will extend. This relation is shown more clearly in Fig. 3. In the metallic disc, the ratio of the diameter of the hole to the largest dimension of the seed should be in the range of 1.5:1 to 5:1, when hole 41 is designed to circumscribe the seed.

The exact mechanism (or mechanisms) by which discs, or layers, of these diamond nucleation suppressor materials located in the manner described function to reduce or eliminate diamond nucleation in the vicinity of the diamond seed 39 is not known for certain. However, it has been found that in this way diamond nucleation can be held back at least until the seeded growth becomes quite large, well formed and capable of accepting the full carbon flux presented thereto during operation at temperature differentials with which in identical systems without the nucleation suppression disc, spurious diamond nucleation resulted in a clustered mass of diamond ) growth.

As is shown in Fig) 4, the developing new diamond projects into bath 43 (Fig. 4 is drawn for an arrangement in which layer 42 is dissolved by the catalyst-solvent metal) as it grows. After termination of the run and reduction of i temperature and pressure to permit removal of the reaction - 20 4 3 3 14 vessel 30, the new diamond growth embedded in the now solidified metallic catalyst-solvent 43 readily detaches from the seeding site(s). The diamond(s) so prepared is easily removed by breaking open the mass 43. Any recess or surface roughness may be then polished away.

Processes carried out in such an apparatus are illustrated in Examples 1-5 hereinafter.

NUCLEATION SUPPRESSION AND EXTENDED CATALYST-SOLVENT In a second preferred embodiment, the process and io apparatus of this invention will employ a nucleation barrier having at least one opening therein and there will be present at least one small lump of catalyst-solvent material extending through the opening to interconnect the mass of catalyst-solvent material and a volume containing the diamond seed material. Referring to Fig. 5, the reaction vessel has many features of construction common to those described above with reference to Fig. 2. Operational techniques are also the same. Throughout the descriptions to follow, elements corresponding to those previously described have corresponding numerical designations.

In Fig. 5, nucleation suppressing layer 42 is disposed in contact with the bottom of mass 43 of metallic catalyst-solvent and between mass 43 and disc 38. A nib 43' of mass 43 projects through hole 41 in layer 42 into disc 38 to make contact with 1-4one exposed face (preferably the cube face) of diamond seed 39. Seed 39 is embedded in disc 38 below the major surface of the disc with a face being exposed by hole 38' in the major surface.

More than one such nib 43' may be used, if desired, in which case a separate seed will be provided for each nib 43'.

Preferably, holes 38' and 41 are coaxial and of the same diameter. This deposition of parts may be best seen in Fig. 6.

The temperature differential between the hot part of the cell (about half-way up the height of the vessel) and the diamond LO pocket is preferably in the range of 20-30°C. This differential depends upon the construction of the vessel, e.g., depth and location of mass of metallic catalyst-solvent, differential resistance in the heater tube, thermal conductivity of the end discs, etc. Thus, the thickness and vertical placement of plug 42 helps .5 determine the temperature differential prevailing in the reaction vessel. With a thicker mass of catalyst-solvent the temperature difference is greater.

The reaction vessel construction shown in Figs. 5 and 6 simultaneously functions hoth to suppress spontaneous diamond nucleation and to reduce the flaw content in the main body of diamond grown from a diamond seed. The dimensional criteria for the layer or disc 42 are the same as those described above under Nucleation Suppression except that nib 43' is not covered by layer 42. In the construction of Figs. 5 and 6, if the disc 42 is made of one of the metallic materials listed above, there must be space between the diamond seed 39 and the closest portion of disc 42 and the material of disc 38 will extend into this space.

Experiments with different reaction vessel constructions have verified the excellent nucleation suppressing capabilities of cobalt and natural mica and the useful nucleation suppressing capabilities of tungsten. In the g same manner, the lack of utility of synthetic mica, platinum and nickel (as well as molybdenum, see Example 6) as nucleation suppressing materials, has been demonstrated.

With respect to the growth flaws, it has been found that by placing the small projection or lump of catalyst10 solvent metal 43’ into contact with the diamond seed material, the starting growth flaws collect in this small protrusion.

By the time the diamond growth has advanced through nib 43' and has reached the main pool of catalyst-solvent metal 43, the proper growth pattern is established and flaw-free (or substantially flaw-free) growth occurs from this point on as the continuing new growth enlarges and projects into pool 43, If nib 43' is made as a circular cylinder, the diameter thereof will be in the range of from greater than 0.020 to 0.100.As used hereto means inches. For nibs prepared to 2C other configurations, the cross-sectional area transverse to the axis of reaction vessel 30 at some location along the nib should be the equivlent of a circular cross-section having a diameter in the range of from greater than 0.020 to 0.100. When cylindrical nibs having a diameter greater than 30 mils (.030) have been used, a projection of diamond solidly attached to the new diamond - 23 3 4 4 growth develops from the former nib. This projection contains the starting growth flaws and would he ground off in converting the new diamond growth into some desired configuration, e. g., a gem cut.

The height (from seed 39 to mass 43) of nib 43' should be in the range of from about 30 to about 60 mils.

As an example of a non-cylindrical nib, nib 43' may be conical with the point thereof in contact with seed 39. Also, nib 43' need not be made integral with mass 43, but may initially be > a separate lump therefrom and in direct contact therewith, so long as it is made of, or contains sufficient, catalyst-solvent.

For example, a catalyst-metal lump interconnecting mass 43 and seed 39 could be in the shape of a cube, sphere or other shape made of nickel or certain nickel-iron alloys providing i that a large enough seed diamond is used to survive loss of carbon to the lump. The catalyst-solvent of which such a separate nib 43' made (or which the plug contains) in a given reaction vessel conduction should have a melting point when in contact with diamond which is higher than the melting point > of the mass of catalyst metal 43 when in contact with diamond.

Because of this capability of nib 43' to collect initial growth flaws, if a large enough seed diamond is used, some etching of the diamond by the nib metal can be tolerated in exchange for the gain in time afforded to this construction. j Processes carried out in such an apparatus are illustrated ih Example 7. 3344 NUCLEATION SUPPRESSION WITH CONTROLLED GROWTH PATH In a third preferred embodiment, the reaction vessel and process will Include an opening in the nucleation suppressing barrier layer adapted to comprise a restricted diamond growth path extending throu^i the barrier and interconnecting the mass of catalyst-solvent material and a volume containing diamond seed material. Referring to Fig, 7, reaction vessel 30 is of the general type and construction disclosed above. Operational techniques for applying both io high pressures and high temperatures in this apparatus are as described above.

Referring to Figs. 7 and 8, salt plug 38 containing pocket 39' of diamond crystals (or a single diamond, if desired) is disposed within salt sleeve 37 resting upon salt plug 36.

Directly thereabove is located inert barrier disc 42 having at least one fine wire extending through the thickness thereof with the lower end thereof in contact with the pocket 39' of diamond crystals and the upper end thereof in contact with the under surface of the main catalyst-solvent mass 43 to serve as the restricted diamond growth path(s). Inert barrier disc 42' is made of a material insoluble in the molten catalystsolvent, preferably of sodium chloride. This disc may, however, be made of CaFg (providing that adjacent reaction vessel components are made of materials compatible therewith); refractory oxides, such as AlgOg, MgO, ZrOg, CaO. SiOg, ThOg and BeO, for example; natural mica; high melting point silicate glasses (e. g,, borosilicate) not reduced by hot carbon; porcelain - 25 13 34-4 or silicates (e.g., MgSiOj or pyrophyllite fired at 750°C. to drive off water). The thickness of disc 42 should be in the range of from about 0.010 to 0.030.

Wires 47, 48 such as are shown In Fig. 8 or holes 5 49, 50 as shown in Fig. 9 may extend straight through disc 42, may have a zigzag configuration or may be disposed in other than the perpendicular direction. In the embodiment of Fig. 8, wires 47, 48 preferably have a diameter ranging from about 0.001 to 0.020 inch (or equivalent cross-sectional area for non-circular wires) and, when feasible, are molded into the plug. The upper (hotter) end of the wires 47, 48 must make contact with metallic catalyst-solvent 43 and the cooler end of the wire must touch diamond in pocket 39' (or graphite in pocket.39' which will be turned into diamond).

Pocket 39s will contain at least one diamond crystal and may contain as much as 30 percent by weight of graphite.

It is preferable to have a small concentration of catalystsolvent metal located in pocket 39’ to minimize any erosion of wires, such as wires 47, 48. This metal may be present as a disc disposed between the contents of pocket 39’ and the ends of the wires. The amount of catalyst-solvent metal used may range from 10-50% by weight when used based on the amount of diamond crystal and graphite.

The diamond growth path(s) are of (or in the case of holes 49, 50 become filled with) some catalyst-solvent metal having a melting point in contact with diamond comparable to the melting point of the catalyst-solvent mass 43 in contact with diamond. Either a single or a plurality of diamond growth paths may be provided depending on the size of. the catalystsolvent bath and the size of diamond growth desired.

The nutrient material 44 may be composed of a carbon source as described above. lo When operating pressure and temperature are reached, the metallic catalyst-solvent 43 in contact with diamond In nutrient layer 44 melts first. The melting proceeds from top down, any graphite in mass 44 of nutrient is converted to diamond and diamond dissolves in the catalyst-solvent.

Wires 47, 48 of catalyst or catalyst alley melt and finally earborrrich molten catalyst- solvent is placed in flew ccrrmunication with diamond pocket 39’ and the carbon begins to cane out of the solution as diamond using the surface of diamond in contact with the cooler end of molten wires 47, 48 as its template. The diamond growth proceeds up molten wires 47, 48 to catalyst-metal bath 43, each wire presenting at its upper end discrete single seeding intact for initiating the large crystal growth, which projects into bath 43 as it develops. The size to which the large crystals (not shown) will develop depends upon the volume - 27 4 3 3 14 available in bath 43 for enlargement and the time of the run. If more than one large crystal is being prepared, the length of the run should be terminated before collision occurs between the developing crystals.

In the case of the embodiment of Fig. 9, openchannels 49,50 with diameters in the same range as wires 47, 48 are employed in place of wires as in Fig. 8. The operation thereof is substantially the same in that at operating pressures and temperatures (if a strong material θ such as natural mica is used), the channels remain open sufficient to provide passage of molten catalyst-solvent 43 to diamond pocket 39’. This catalyst-solvent so located creates molten wires in situ enabling the- transport of carbon to the cool end,whereby diamond growth can initiate g and proceed up through channels 49, 50 to the upper side of disc 42'and thereby provide a single seed for each hole, or channel, provided.

The diamond growth paths (wires 47, 48 or holes 49, 50) survive as long thin strands of diamond, e.g., diamond ' whiskers. After termination of the run and reduction of temperature and pressure to permit removal of the reaction vessel 30, the new diamond growth embedded in the solidified metallic catalyst-solvent 43 is easily removed by breaking open the mass 43, If desired, the diamond whiskers may be recovered by dissolving salt disc 38.

During decompression, the connection is usually broken between the diamond whisker of each growth path and the diamond grown from the seeding provided thereby apparently due to the concentration of stress at this point. Depending β upon the cross-sectional area of the growth path, an amount of the new growth is broken out leaving a rough indented face. The smaller the cross-sectional area of the growth path, the shallower the depth of the broken out portion.

In the case of gem quality diamonds, this damaged face must be ground smooth and minimal damage of this type will provide larger size polished gems. The maximum diameter of 0.020 (or equivalent cross-sectional area) for any growth path enables both the use of multiple seeds in pocket 39’ (while insuring the presentation of a single discrete seed to mass 43 via each growth path) and also minimizes the aforementioned damage.

Care must be taken in the assembly of the reaction vessel of this invention. Failure to obtain diamond growth has in many cases been traced to poor cell assembly in which shifting of the wires occurred and failed to make contact with the contents of pocket 39'.

The formation of diamond materials by this preferred feature of the invention is illustrated in Examples 8 to 16, hereinafter.

NUCLEATION SUPPRESSION AND SUPPRESSION OF SEED EROSION In a fourth preferred embodiment of the invention, the apparatus includes an isolation barrier having a melting point when In contact with diamond which is higher than the 5 melting point of the mass of catalyst-solvent when the mass is saturated with dissolved carbon. Referring to Fig. 10, reaction vessel 30 is of the general type and construction disclosed above. Operational techniques for applying both high pressures and high temperatures in this apparatus are 1® as described above.

Referring to Fig. 10, the bottom end of cylinder 37 encloses the embedment disc 38 having at least one diamond seed 39 embedded therein. If a plurality of diamond seeds, they would be located in spaced locations with one at each location.

Diamond seeds are preferably 1/4 to 1/2 mm in size and having a cube face, hut diamond may be seeded from any face. Preferably, all of the underside of plug 43 of metallic catalystsolvent is covered with means for suppressing diamond nucleation over a preselected area (e.g., disc, or layer, 42) except, perhaps, for a hole therethrough as shown in Figs. 12-16. Isolation means 51 are initially disposed between diamond seed 39 and the catalyst-solvent in order to prevent premature contact therebetween such as would result In dissolution (partial or complete) of seed 39. The upper surface of diamond seed material 39 should be oriented with a well-formed face, e.g., a cube face in contact with the underside of disc 51. - 30 43344 Seed isolation disc (barrier layer) 51 is preferably made of platinum but may be made of a metal selected from any of the metals in the group consisting of platinum, molybdenum, titanium, tantalum, tungsten, iridium, osmium, rhodium, palladium, vanadium, ruthenium, chromium, hafnium, rhenium, niobium and zirconium and alloys of these metals. By preventing damage to the exposed seed face, the isolation or barrier metal prevents the occurrence of diamond growth from more than one locus on the seed face. When such protection is not provided, erosion of the diamond seed material occurs. Considering a given diamond seed, the erosion may either completely or partially destroy the seed. In the former case, diamond nucleation can occur at spaced loci at the underside of the catalyst-solvent mass and in the latter case, diamond growth usually proceeds from different loci on the eroded seed.

Resultant new diamond growth in either case is lacking In coordination between the multiple growths and many flaws develop at the interface(s) when these separate growths meet.

In any given reaction vessel construction, different materials are employed for each of a) the catalyst-solvent material, b) the isolation barrier layer and c) the nucleation suppressing layer. Nucleation suppressing layer 42 is composed of materials defined above. When disc 42 is made of mica, polycrystalline high-density alumina, quartz, silica glass or other material presenting a layer with which the molten catalyst-solvent system will not alloy and/or cannot penetrate, it is necessary 3344 to provide hole 41 (as shown in Figs. 12-14) through disc 42 to accommodate contact between the molten catalyst-solvent bath and disc 51 for eventual contact with seed 39. Disc 42 may, of course, be provided with a hole when made of metal, if desired.

In the case of the isolation means for the diamond seed material (disc 51), physical contact between the catalystsolvent metal and the diamond seed is prevented until after the catalyst-solvent metal 43 has melted and become saturated with carbon from the nutrient mass 44. The timing is such that this carbon saturation occurs before barrier layer 51 is dissolved by the molten catalyst-solvent. Once barrier layer 51 becomes dissolved in the molten catalyst-solvent, the exposed face of the diamond seed 39 sets the pattern of growth and development of the new growth may proceed.

Even those isolation disc materials listed which form carbides that are stable with respect to diamond at the pressures and temperatures employed, function well since the carbide forming process is slow compared to the speed with which the pool of catalyst-solvent metal becomes saturated with carbon. Any carbide formed eventually dissolves in the pool of catalyst-solvent metal. There was no evidence that platinum formed a carbide more stable than diamond.

In each of Figs. 12 and 13, a projecting portion of embedment disc 38 presents barrier layer 51 into contact with the underside of mass 43 of catalyst-solvent. Embedded seed 39 is disposed directly under disc 51 with a single face thereof in direct contact with disc 51. In Fig. 12, the material of which disc 38 is composed should separate seed 39 from the wall(s) of hole 41. Thus, In the case of the arrangements of Figs. 12 and 13, when nucleation suppressing disc 42 is non-metallic (and a cube face of seed 39 is offered as template for the new diamond growth), the relationship between the diamond seed and new growth 54 will be as shown in Fig. 17. It is advantageous not to have the new growth envelop the seed at all, because much less of the new growth will need to be polished away to remove flaws.

The arrangement shown in Figs. 11 and 14 permits the production of new diamond growth as shown in Fig. 17, when nucleation suppressing layer 42 is metallic and thereby dissolved by the molten catalyst-solvent. As previously mentioned, the growth configuration shown develops when a cube face of seed 39 is in contact with barrier layer 51. Projection 43’ of the catalyst-solvent fits closely to the wall(s) Of hole 41 anti projects through the hole to contact barrier layer 51 over seed 39. 14 The advantage of using both the barrier layer and the nucleation suppressing layer may be assessed as follows. When only the barrier layer is employed, about 70% of the attempts to grow single, large, high quality diamonds will g encounter spontaneous diamond nucleation and interference tilth growth of the new diamond growth from the seed. Sometimes this interference is not serious, hut most often the growth from the seed is badly damaged. When a nucleation suppressing layer is used, the improvement is so dramatic IQ that only about 30% of the attempts to grow single, large, high quality*diamonds will encounter spontaneous diamond nucleation. In fact, since the use of natural mica has been instituted, spontaneous diamond nucleation has not occurred in a single instance.

The arrangements shown in Figs. 15 and 16 are useful, when solid non-metallic nucleation suppressing layer materials such as mica or machinable alumina are employed. In each case, a small hole 52 is drilled or punched through disc 42. This hole is preferably in the range of from 0.001 to 0.020 inch In diameter. In the arrangement of Fig. 15, when the catalystsolvent material 43 becomes molten, it passes through hole 52 and, after a period of time, alloys with and melts isolation disc 51 thereby reaching diamond seed 39 to initiate diamond growth back up through hole 52 to provide seeding !5 for diamond growth above layer 42. In the arrangement of Fig. 16, a wire 53 occupies hole 52. The wire may, for example, be of nickel, Fe-Al or Fe-Ni alloy and extends through disc 42 to contact both plug 43 and isolation barrier 51. As the catalyst-solvent material 43 and then the material of wire 53 become molten and carbon is dissolved therein, the isolating barrier 51 alloys and diamond growth begins for supplying a seed at the upper side of layer 42.

The means for maintaining temperature differential between the hot part of the vessel (about half-way up the height of the vessel) and the diamond pocket, are as described above. Illustrative processes relating to this preferred feature are found in Examples 17 to 24, hereinafter.

COLORING AND PATTERNING In a fifth preferred embodiment, the reaction vessel and process will include at least one barrier in combination with an additional component selected from dopants, getters, . compensators and mixtures thereof·, to provide colors, patterns and color zones, in the diamond product. Referring to Fig. 18, reaction vessel 30 is of the general type and construction disclosed above. 344 Referring to Fig. 18, cylinder 37, together with plug 36 and cylindrical plug 46, define volume 55 adapted to contain a cylindrical charge assembly as, for example, is shown in each of Figs. 19-22. These charge assemblies permit a) the introduction of quantities of boron and aluminum to make possible a unique star diamond and/or b) the successive introduction into the growing diamond of varying coloration in a single large diamond crystal. Any of the elements and combinations disclosed above can be used to form such charge assemblies.

By making simultaneously available to the developing diamond at least 1 part per million (ppm) of boron and 2500 ppm of aluminum by weight of the catalystsolvent employed and properly orienting the diamond seed, a gem diamond crystal can be grown symmetrical about a cube axis and displaying a colorless or white pair of 3 dimensional linearly-extending bands in crossed relationship when the crystal is viewed along the given axis of symmetry with the balance of the crystal having a blue color. The overall appearance of the pattern seen appears to be symmetrical.

In addition, a crystal can be formed in which colored diamond growth is enclosed within colorless diamond growth. Similarly, the first colored diamond growth may be enclosed within a second colored diamond growth. A variety of color combinations may be obtained depending upon the selection of - 36 43344 dopants, getters and/or compensating materials. For example, nitrogen will produce color values ranging from yellow to green diamond, boron yields deep blue color diamond and aluminum, titanium and zirconium each favor colorless diamond growth.

Ordinarily, there is enough nitrogen present in the metallic catalyst-solvent metal and all reaction vessel components to strongly color diamond yellow whether produced by either the thin film method or the temperature gradient method. Typical nitrogen content is about 30-40 ppm. Thus, in the practice of this invention wherein diamonds made by the thin film method are typically used in the mass of nutrient, the resulting diamond will be yellow in color (rich in nitrogen) in the absence of the addition of getter, compensator and/or dopant to the system.

Boron (and, of course, nitrogen) functions as a dopant. Aluminum functions as a getter for nitrogen and, if sufficient quantities of aluminum are present, will enter the lattice of the growing diamond and act as a compensator for such nitrogen as may enter the lattice. Titanium and zirconium each function as getters.

Contrary to earlier teachings, it has been found that boron will not readily render diamond a blue color unaided. Thus, if as little as about IDO ppm of aluminum is present in the molten catalyst-solvent 20 micrograms of boron will turn diamond a deep blue. With no aluminum present, the diamond growth will be yellow-green unless large quantities (in excess of 20 mgms) are present in the catalyst-solvent bafh.

Since commercial borons contain as much as 900 ppm of aluminum, such boron will inherently produce a blue-colored diamond if used; particularly since aluminum is usually present as an . impurity in the eatalyst-solvent metal.

Thus, as is disclosed in U.S. Patent 3,148,161 10 Wentorf, Jr. et al (column 5, lines 42-46 and column 9, lines 43-46) by using boron in a concentration from 0.1 to 20% by weight of the graphite (to be converted to diamond) a.shade of color ranging from blue to deep purple will result, but the boron used contains traces of impurities including L5 aluminum. However, calculations of the total amount of boron additive taught hy Wentorf, Jr. et al (assuming commercial boron were to be used having a 900 ppm content of aluminum) . establish that the maximum aluminum that would he introduced to the system using the Wentorf, Jr. et al teachings is 200 !O ppm (based on the mass of catalyst-solvent), whereas the minimum amount of aluminum required for '’star formation (crossed white hands in a blue field) appears to be about ' 2500 ppm (based on the mass of catalyst-solvent).

The production of successive colors during growth is accomplished by the use of combinations of dopant, getter and/or compensator materials arranged In the structure of the charge assembly whereby inttally the growth medium will produce some preselected colored diamond growth and after a preselected period of diamond growth getter and/or compensator material enters the molten catalyst-solvent and causes growth of colorless color (or growth of a different color, as desired) to envelop the initial colored growth in an uninterrupted sequence.

J Charge assembly 40 (shown in Fig. 19) has been used 10 for the successful production of dark blue star diamonds.

However,· by introducing a layer of non-metallic nucleation suppressing material, e.g., mica (as described in connection with Fig. 20 below) the arrangement shown in Fig. 19 can be made much more reliable. Seed 39 is protected by seed Isola15 tion disc (barrier layer) 51 which is preferably made of platinum but may be made of any metal described above for this purpose.

By using isolation disc 51, physical contact between the melted pool of catalyst-solvent metal and the diamond seed is prevented until after the pool of catalyst-solvent metal 43 has become saturated with carbon from nutrient mass 44. The timing is such that this carbon saturation occurs before barrier layer 51 is dissolved by alloying with the molten catalyst-solvent. When such protection is not provided, erosion of the diamond seed material occurs as described above.

Seed 39 is embedded in embedment layer 38 with a cube face exposed and In contact with disc 51 to provide the proper template for the new diamond growth. Mass 43 of metallic catalyst-solvent is disposed thereabove with disc 51 in contact with the underside thereof and a layer 44 of nutrient material (such as a carbon source as described above, e.g., diamond plus a minor graphite content above the catalyst-solvent) containing boron.

Bor^n-eontalning diamond for layer 44 may be readily LO prepared as taught in the aforementioned Wentorf, Jr. et al patent using commercial boron containing sufficient aluminum. The use of boron-doped diamond Is preferred since such small concentrations of boron are needed (in excess of 1 ppm on the weight of the catalys-solvent), however, the boron can be L5 supplied in other ways. Thus, a small crystal of boron or . boron carbide may be disposed in layer 44.

The requisite aluminum content (at least 0.25% by weight of the catalyst-solvent) may best be provided by ' using an aluminum alloy of the catalyst metals, e.g., Fe + 3 !O Wt. % Al.

Aside from provisions for boron content, the nutrient material 44 may be composed of a carbon source as defined above.

As operating pressure and temperature are reached, the metallic catalyst-solvent 43 in contact with any graphite in nutrient 44 melts converting this graphite to diamond. Catalyst-solvent in contact with the diamond in layer 44 melts at slightly higher temperatures and dissolves the diamond.

The melting catalyst-solvent progresses into layer 44 and the melting proceeds from top down in layer 43. In this manner, when carbon-rich molten catalyst-solvent reaches and alloys with layer 51, It already contains boron and aluminum ready for entry into the new diamond growth that is initiated when the molten-catalyst metal reaches the cooler diamond seed 39 and deposits carbon from solution. Some of the aluminum getters some of the nitrogen in the system, still other of the aluminum enters the diamond lattice. Some of the aluminum entering the lattice acts as a compensator for any nitrogen in the lattice tying up electrons of the nitrogen atoms whereby these nitrogen atoms become optically inactive. The rest of the aluminum is uncompensated and for some unknown reason, collects In elongated, thin vertically extending planar zones in crossed relationship to each other. These zones appear white in contrast to the dark blue of the rest of the diamond growth. When viewed in the direction of the cube axis of symmetry (I.e., from the top of the diamond as it is formed in layer 43), these zones appear as crossed bands perpendicular to each other extending toward opposite corners of the crystal. “ 3 3 4-4 The charge assemblies of Figs. 20-22 are arranged for the production of successive colors during uninterrupted growth of a single crystal. In each of these cell assemblies seed 39 is protected by isolation disc 51 and embedded in g layer 38 with some desired orientation. The nutrient (except for additions of dopant, getter and/or compensator) is the same as described for layer 44. Also, each of these charge assemblies utilizes diamond nucleation suppressing layer 42 (or 42').

Nucleation suppressing layer 42 is composed of a material LO different from both the catalyst-solvent employed and isolation disc employed in any given charge assembly and is selected from the group of materials described above. The advantage of using both the barrier layer and the nucleation suppressing layer have been been described above.

L5 In Fig. 20, the provisions for producing successive zones of coloration are the separate plugs 43, 56 of catalystsolvent, dual nutrient layers 44, 57 and getter and/or compensator disc 58.

With this arrangement, to prepare a diamond crystal having :o a yellow or green core covered with colorless growth, metallic catalyst-solvent layer plug 43 should be substantially free of aluminum, titanium, zirconium and manganese but may otherwise be any of the recognized catalyst metals and alloys. For a yellow core nutrient layer 44 should have diamond of uncorrceted - 42 43344 nitrogen content. Similarly, catalyst-solvent layer 43 will contain nitrogen contamination normally encountered. Thus, in the absence of special effort to offset the nitrogen normally present, this nitrogen content will dope the initial g diamond growth developing on seed 39 giving this initial growth a deep yellow color. Colorless growth can then be applied by using non-aluminum-containing catalyst-solvent plug 56 in combination with a disc 58 of aluminum, titanium or zirconium.

A high concentration of aluminum (from 1 to 10% by weight of the Ιθ metallic catalyst-solvent) will insure colorless growth once the nutrient fh layer 44 has been used up.

If the initial yellow color is to develop, care must be taken to Insure a delayed diffusion entry of any significant amount of aluminum, titanium or zirconium into the melt before the yellow growth has been satisfactorily attained. By the time disc 58 has alloyed into catalyst-solvent layer 56 and worked through the diffusion path afforded by nutrient layer 44, there should be sufficient time delay for yellow core formation.

To develop a green core, very large concentrations of nitrogen are required. This can be accomplished by introducing nitrogen compounds, e.g., iron nitride, which will decompose and release additional nitrogen to the catalyst-solvent system (layer 43).

Various arrangements may be used to increase the delay time before entry of the getter and/or compensator into the diamond-forming medium. Thus, the getter and/or compensator may be recessed into pressure-transmitting plug g 38 in the form of a wire, rod or billet or may be separated from the catalyst-solvent by a thin layer of a high melting point metal, e.g., platinum, iridium, or tungsten.

In order to provide a blue diamond core covered by colorless growth care must be taken that boron and aluminum are present at the same time for the initial growth and that all the boron is used up before the catalyst-solvent plug 56 can be contaminated. The catalyst-solvent for both layers 43 and 56 should contain aluminum (e.g., iron + 1-8 wt, % aluminum). The boron dopant should all he located in the lower region of L5 nutrient layer 44. Non-metallic nucleation suppressing materials e.g., mica should be used for layer 42. Provisions for the colorless aftergrowth would he the same as described for the yellow colorless combination.

Fig, 21 is designed in much the same manner for the preparation of a yellow or green core as in the arrangement In Fig. 20, A single catalyst layer 43 is used In combination with separate nutrient layers 44, 57 with getter and/or compensator disc 58 disposed therebetween. The composition of catalyst-solvent layer 43 and nutrient layer 44 will determine whether the core of the new diamond growth will be yellow or green as described in connection with Fig. 20.

Fig. 22 is specific to preparing a blue core diamond utilizing a localized concentration of boron atoms located ln disc 59 as an alloy or compound of boron.

Subsequent growth (after the boron atoms are used up) may he colorless, pale yellow or pale green, if desired. Catalyst-solvent metal layer 43 preferably contains aluminum to permit blue coloration by the boron. The nucleation lo suppressing layer 42 should be non-metallic. Nutrient layer 44 In combination with the amount of aluminum in layer 43 will determine whether the later-applied growth will he colorless, pale yellow or pale green. Also, if a large enough concentration of aluminum Is present in catalyst-solvent layer 43, the initial growth can be a star.

Means for achieving temperature differential between the hot part of the vessel (about half-way up the height of the vessel) and the diamond pocket are as described above.

Preferred catalyst-solvents for the practice of the color 20 ing features of this invention are Fe, FeNi, FeNiCo, Fe-Al, Ni-Al, Fe-Ni-Al and Fe-Ni-Co-Al. Preferred nucleation suppress ants are natural mica and cobalt and the preferred isolation 3 4-4 barrier is platinum. When natural mica is used, it should first be fired as directed hereinabove. When alloys of higher iron content are used, the diamonds produced have a lighter yellow color. With larger amounts of Ni and/or Co, the g resulting diamonds have a deeper yellow color.

For the reaction vessel construction described, the preferred pressures range from 55-57 kilobars (kb) and preferred temperatures are in the 1330-1430°C, range.

EXAMPLES In each of the following Examples 1-5, the reaction vessel configuration provided a temperature differential in the 20-30’C range, the nutrient consisted of 1 part by weight SP-1 grade graphite sold by Union Carbide Corporation and 3 parts by weight 325 mesh diamond (i.e. diamond which passes through a mesh having 325 holes per linear inch prepared by the thin film method, seeds used were 1/4 to 1/2 ran, the catalyst-solvent is 70Ni30Fe and temperatures were measured using a Pt/Pt 10 Rh thermocouple: EXAMPLE 1 Pressure ...57 kb Temperature (l4.0-14.2 mv) ...1430-1450°C Nutrient ...210 mgm Nucleation Suppressing Layer' ... None ' Time ...24 hours At least 10 yellow diamond crystals grew together in a cluster. The 1/2 mm seed had dissolved a.little and had grown back in. The crystals were either octahedra or cubooetahedra.

EXAMPLE 2 Pressure ...57 kb Temperature (14.0-14.2 mv) ...1430-1450’0 Nutrient ...210 mgm Nucleation Suppressing Layer ...5 mil Fe disc with an 80 mil hole (as in Fig. 2) Time ...5 hours, 4o min.

Only one yellow diamond crystal grew developing from the diamond seed. There was no spurious nucleation of diamond. The crystal was an octahedron with small cube faces at the points.

EXAMPLE 3 Pressure Temperature (14.0-14,2 mv) Nutrient Nucleation Suppressing Layer ..57 kb ..1430-1450°C .. 210 mgm .. as in Example 2 but slightly smaller in diameter than plug 43 Time ... 31 1/2 hours Weight of Seeded Growth ...43.7 mgm Single seeded growth developed, well-shaped, symmetrical and relatively flaw-free. The crystal was a yellow octahedron with small cube faces at the points. A small diamond crystal developed where the underside of plug 43 was not covered with the Fe disc 42. This experiment confirmed the nucleation suppressing capabilities of Fe. There was, however, partial dissolution of die seed before new growth began.

EXAMPLE 4 Pressure, temperature and nutrient weight were the same as in Example 1 and no nucleation suppressing layer was employed. The time was 24 1/2 hours. As in Example 1, a cluster of yellow crystals developed from spontaneous nucleation.

The seed grew to about 2x2 mm'with a diamond barnacle attached thereto. Also five other individual small crystals grew from spontaneous nucleation.

EXAMPLE 5 Pressure Temperature (14.0-14.2 mv) Nutrient Nucleation Suppressing Layer ...58 kb ...1430-1450*C ...200 mgm ...1 mil Ti disc as in Pig. 2 Time % ...43 hours Weight of Seeded Growth ...147.6 mgm A single light yellow crystal was formed from the seed. There was no spontaneous nucleation of diamond. The flaw content was minor. The crystal had a very low nitrogen content.

Experiments with different reaction vessel constructions have verified the excellent nucleation suppressing capabilities of cobalt and natural mica and the useful nucleation suppressing capabilities of tungsten. In the same manner the lack of utility of synthetic mica, platinum, nickel and molybdenum as nucleation suppressing materials has been demonstrated.

In each of the following Examples 6 and 7 the reaction vessel configuration provided a temperature differential 3 4 4 in the 20-30°C range, the nutrient consisted of 1 part by weight SP-1 graphite (National Carbon Company) and 3 parts by weight 325 mesh diamond prepared by the thin film method, seeds used were 1/4 to 1/2 mm, the catalyst-solvent is 7ONi3OFe and temperatures were measured using a Pt/Pt 10 Bh thermocouple. ,o .5 EXAMPLE 6 Pressure ...56 kb Temperature (14.2 mv) ...1430-1450°C Nutrient ...210 mgm Nucleation Suppressing Layer ...10 mil Mo disc with hole for nib as in Fig. 5 Nib Description ...40 mil diameter x 10 mils in heights integral with mass 43 Time ...45 2/3 hours Weight of Seeded Growth ...about 60 mgm In spite of the failure of the Mo disc as a nucleation suppressing material, a beautiful, yellow, clear growth developed from the seed. Four other diamond crystals grew spontaneously, collided and interfered with optimum seed growth. The nib did function well to prevent flawing in the growth extending into bath 43, however. The seeded growth was in the shape of a truncated octahedron with modifying cube faces. 433 4 4 EXAMPLE 7 Pressure ...57 kb Temperature (14.1 mv) ,..l42O-l44o°C Nutrient ...210 mgm Nucleation Suppressing Layer ...2-5 mil Pe discs one over the other with 40 mil hole in center for nib as in Pig. 5 Nib Description ...40 mil diameter x 10 lo mils in height, integral with mass 43.

Time . ..4l 1/4 hours Weight of Seeded Growth ..,96 mgm A beautiful clear light yellow crystal grew from 15 the seed diamond. No spontaneous diamond nucleation occurred.

The crystal was ln the shape of a truncated octahedron with modifying cube faces. Nib 43' successfully prevented significant flawing in the initial growth of the crystal.

Thus, by making available both the capability for 20 suppressing diamond nucleation and that of eliminating growth flaws from the main body of the new growth a very significant improvement in the controlled growth of large diamonds from diamond seed material has been attained.

Each of the following Examples is representative 25 of gem quality growth. In each of Examples 8-12, the operating pressure was 57 kilobarsj the operating temperature was 1500°C, and the nutrient layer 44 was a mixture of graphite and diamond in a 1:3 ratio (except for the addition of minor amounts of other material in Examples 8, 10 and 11). 34-4 EXAMPLE 8 Catalyst ...700 mem (98$ Iron. 156 aluminum, 1$ phosphorus) Embedment disc 42 ...0.020 thick, NaCl Wire ...0.010 diameter wire of nickel Diamond pocket 39’ ...25 mgm (75$ diamond, 25$ graphite) Time ...23 hours lo Weight of diamond growth . ..14 mgm A single clear diamond (nearly water white) with few internaj. flaws was produced from the wire-induced seeding. The crystal was. '& ‘truncated octahedron with modifying cube faces. ' EXAMPLE 9 Catalyst .

Embedment disc 42 Wire Diamond pocket 39’ ...700 mgm (97-5$ iron and 2.5$ aluminum) ...0.20 thick, NaCl ...single 0.003 diameter wire of nickel ...25 mgm (75$ diamond, 25$ graphite) Time ...25.5 hours Weight of diamond growth .,.16.6 mgm The single diamond produced from the wire-induced seeding was very pale yellow with only a few minor flaws. This crystal phosphoresced giving off a blue glow under 3 3 4 4 2537 A light. This diamond was not semi-conducting, had a low nitrogen content and was a truncated octahedron with modifying cube faces.

EXAMPLE 10 Catalyst Bnbedment disc 42 Wires % Diamond pocket 39' Time Weight of diamond growth ...700 mgm (92.5# iron, 7.5# aluminum) plus about 10 ppm of boron in the form of B/jC ...0.020 thick, NaCl ...0.005 diameter nickel wire and one 7 mil diameter invar wire ,,.25 mgm (75# diamond, 25# graphite) plus nickel disc 2 mils x 187 mils in diameter ...about 43 hours ,..18 mgm (from nickel wire only) Die single diamond crystal resulted from the seeding provided by the nickel wire. Examination disclosed that the invar wire had not properly contacted contents of the diamond pocket 39’· The crystal was deep blue, semi-conducting, phosphoresced feebly and was a truncated octahedron with modifying cube faces.

EXAMPLE 11 Catalyst ...700 mgm (97# Iron, 7# aluminum) plus 5 ppm boron Embedment disc 42 ...0.020 thick, NaCl - 534 3 3 4 4 Wire ...single 0.005 diameter nickel wire Diamond pocket 39* ...25 mgm (75$ diamond, 25?$ graphite) plus nickel disc 2 mils x 137 mils in diameter Time ...93 hours Weight of diamond growth ...52 mgm The single crystal developed from the wire-induced 10 seeding was pale blue in color, semi-conducting and phosphoresced brightly under 2537 A, ultraviolet light. This crystal was a truncated octahedron with modifying cube faces.

EXAMPLE 12 Catalyst Babedment disc 42 Wires Diamond pocket 39’ ,..700 mgm (97$ iron, 3$ aluminum ...0.020 thick, IlaCl ...six 0.005” diameter nickel wires ...a single diamond 2-3 mm seed was used,, oriented with octahedral face up in contact with wires Time Weight of diamond growth Six colorless diamond crystals were produced (one 25 from each wire-induced seeding). The six diamonds grew in parallel crystallographic orientation with an octahedral face up. ...52 hours ...six crystals averaging about 14 mgm In each of the following Examples 13-17 the operating pressure was 55 kilobars; the operating temperature was in the 1450-1500°C range and the length of the run was 5 hours The nutrient layer 44 was a mixture of graphite ahd diamond in a 1:3 ratio and the catalyst mass was of nickel-iron alloy (51 Ni 49 Fe). In all examples in whieh wire served as the growth path, nickel wire was used and a disc of Femico (FeNiCo) alloy (0.002 thick; '.Ό.Ι87 in diameter) was disposed in contact with and between the growth paths and the diamond in seed pocket 39 * - some instances requisite contact was not made during loading of the cell and no growth occurred. The seed pocket 39’ consisted of 0,025 g of a mixture of diamond and graphite in a 3:1 weight ratio. In all examples crystals grown from the restricted diamond growth paths ranged from about 3/4 to 1 mm in size and were clear yellow in color.

EXAMPLE 13 Embedment disc 42 ...0.028 thick, NaCl Growth paths ...one 0.005 diameter wire ...one 0.010 diameter wire ...one 0.020 diameter wire Diamond growth ...a single crystal grew from the two larger wire growth paths; no crystal grew from the 0.005 diameter wire. i 3 3 4 4 EXAMPLE 14 Embedment disc 42 ... 0.02311 thick pyrophyl lite (alumina-silicate) fired at 750° C Growth paths ...One 0.005 diameter wire one O.OIO diameter wire one 0.020 diameter wire Diamond growth ...each growth path produced a single crystal 0 EXAMPLE 15 Embedment disc 42 ...0.028 thick machinable alumina Growth paths ...one 0.005 diameter wire one 0.010 diameter-wire j one 0.020 diameter wire Diamond growth ...one crystal grew from the 0.005 growth path; 3 ηό growth from the other growth paths (wires shifted during assembly).

EXAMPLE 16 Embedment disc 42 »ao0o27 thick machinable MgO Growth paths ...one O.OIO diameter wire Diamond, growth j ...one 0.020 diameter hole ...no crystal developed from the O.OIO diameter wire; a single crystal grew from the hole and several small crystals grew along a crack in the MgO that . occurred during loading of the reaction vessel.

The length of the restricted diamond growing path from seed pocket to catalyst-solvent bath is not critical so long as the distance to the diamond pocket 39* from the hot region of the reaction vessel permits a temperature high enough for rendering molten the catalyst-solvent path (e.g. wires 47, 48) where it contacts the diamond seed material. The preferred length ls in the 20-40 mils range.

In bach of the following Examples 17-24 the reaction vessel configuration provided a temperature differential in the 20-30°C range, the nutrient consisted of 1 part by weight SP-1 (National Carbon Company) graphite and 3 parts by weight 325 mesh diamond prepared by the thin film method, seeds used were 1/4 to 1/2 mm and temperatures were measured using a Pt/Pt 10 Eh thermocouple.

EXAMPLE 17 Pressure ...57 kb Temperature (13.2 mv.) ...1340-1360°C Catalyst ·..51Ni49Fe Nutrient ...210 mgm Nucleation Suppressing Layer ...5 mil Fe disc covering all of bottom of catalyst-solvent mass J ' · EXAMPLE 17 - cont'd Isolation Barrier ...5 mil Ta disc coextensive and contiguous with Fe disc Seed Arrangement ...5 seeds in spaced relation in contact with Ta disc Time ...22 hours 40 min Four yellow crystals were produced, one growing from each of four seeds. One seed produced a cluster. The new diamond growth varied in size from 10-20 mgm (1/20-1/10 carat). The crystals had. small inclusions near one face but were otherwise clear. In each case the crystal habit was cubo-octahedral with modifying cube faces.

EXAMPLE 18 Pressure ...57 kb Temperature (13.9 mv) ...1400-1420’C Catalyst ..,51Ni49Fe .

Nutrient ...210 mgm Nucleation Suppressing layer ...none Isolation Barrier ...1 mil W disc covering all of bottom of mass of catalyst-solvent Seed Arrangement ...5 seeds in spaced relation in contact with Ta disc Time ...5 hours Five light yellow crystals resulted, one developed from each seed. The new growth had an average size of 1.52 mgm and each measured about 1 mm along a cube face. The - 58 43344 crystals were well-formed, clear and relatively free of inclusions. In each case the crystal was cubo-octahedral with modifying cube faces.

With multiple seeding the requirement for nucleation suppression is reduced and with proper operating conditions and a seed population density of 1 seed 8-10 mm^ the nucleation disc can be dispensed with.

EXAMPLE 19 Pressure ...56 kb Temperature (13.4 mv) ,..1360-1380’C Catalyst .·.51Ni49Fe Nutrient ...450 mgm - Nucleation Suppressing Layer ...5 mil Co disc with 150 mil dia. hole Isolation Barrier ...1 mil Pt disc as in Pig.12 Seed Arrangement ...as in Fig. 12 Time .,.67 hours Weight of Diamond Growth ...213 mgm The seeded diamond growth was yellow and of gem quality. Three other very small crystals grew out of the region occupied by the seeded growth. Crystal shape was truncated octahedron with modifying cube faces.

EXAMPLE 20 Pressure ...57 kb Temperature (13.3-13-6 mv) ...1360-l400’C 3344 EXAMPLE 20 - cont'd Catalyst ...51Ni49Fe Nutrient ...400 mgm Nucleation Suppressing Layer ...5 mil Fe disc (Fig. 11) Isolation Barrier ...5 mil Mo disc (Fig. 11) Seed Arrangement ...as in Fig. 11 Time ...85 hours Weight of Diamond Growth ...190.4 mgm ίΟ A single beautiful yellow gem crystal developed. The crystal shape was eubo-octahedral.

EXAMPLE 21 Pressure Temperature (13.7 mv) Catalyst Nutrient Nucleation Suppressing Layer Isolation Barrier ...56 kb ...1390-1405°C ...51Ni49Fe ...400 mgm ...9 mil Co disc with 150 mil diameter hole ,..1 mil Pt disc in the 150 mil diameter hole Seed Arrangement ...as in Fig. 12 Time ...68 3/4 hours Weight of Diamond Growth ...156 mgm A single beautiful golden yellow gem was produced in a cubo-octahedron shape with modified octahedral edges.

EXAMPLE 22 Pressure ...56.5 kb Temperature (13.2 mv) ...1345-1360° C Catalyst ...Fe + 3 wt.# Al Nutrient ...500 mgm Nucleation Suppressing Layer ...None Isolation Barrier ...1 x 20 x 20 mils Pt disc Seed Arrangement ...as in Fig. 12 Time ...l6o hours Weight of Diamond Growth ...206 mgm A single beautiful, near colorless crystal was grown. Crystal shape was truncated cubo-octahedron with modifying cube faces; phosphoresces over 1 hour after exposure to 2537 1 light; gives high, substantially flat transmission of ultraviolet light from about 2250 A - 3.30 p and from 6.00 p to 5θ ΜJ is semi-conducting and thermoluminesces. The thermal conductivity of the crystal at 80°K was at least 180 watts/cm’K.

EXAMPLE 23 Pressure Temperature (13.2 mv) Catalyst Nutrient Nucleation Suppressing Layer Isolation Barrier Seed Arrangement ...as in Example 22 ...as in Example 22 ...as in Example 22 ...as In Example 22 ...none ...1 x 20 x 20 mils Pt disc ...as in Fig. 12 3344 . EXAMPLE 23 - cont'd Time ...l6l hours Weight of Diamond Growth ...256 mgm In addition to the seeded growth one other small (22 mgm) diamond crystal grew and interfered slightly with seeded growth, which was colorless and gem quality. The flaws were polished out to produce a 194 mgm crystal. The crystal possessed properties of phosphorescence, ultraviolet transmission, electrical conductivity, thermal conductivity and thermoluminescence as in Example 22. Abrasion resistance was very high. Since very small amounts of diamond are removed in making the grinding wheel abrasion test, measurements are difficult to make accurately when large amounts of corundum are removed. Test results produced grinding J ratios ranging from 120,000 to 168,000 in 3 gm of diamond seed.

EXAMPLE 24 Pressure Temperature 3 Catalyst Nutrient Nucleation Suppressing ; Isolation Barrier Seed Arrangement Time Weight of Diamond ...55 kb ...1300°C ...95Fe5Al (prealloyed) .,.500 mgm Layer ...2 mil natural mica (fired) disc with 7 mil diameter hole ...1 x 20 x 20 mils Pt disc ...as in Fig. 15 ...190 hours h ...140 mgm - 62 A single, nearly flawless crystal was formed.

The crystal was in the shape of a truncated octahedron. In addition to the (111) faces, the crystal had cube faces (100), dodecahedron faces (110) and (113) faces.

Experiments have verified the lack of utility of synthetic mica, platinum, nickel and molybdenum as nucleation suppressing materials.

After termination of each run and reduction of temperature and pressure to permit removal of the reaction vessel 30, the new diamond growth embedded in the solidified metallic catalyst-solvent 43 readily detaches from the seeding site(s). The diamond(s) so prepared is easily removed by breaking open the mass 43. Designations of the diamond seed are schematic and no attempt has been made to show the preferred disposition.

The crystals resulting from the practice of this invention develop in symmetries determined by the face of the seed crystal selected as the pattern. Thus, a diamond crystal grown from a cube face (100) of the seed crystal will be symmetrical about the cube axis and, in the case of near colorless diamonds, such a crystal will result In the unique pattern of phosphorescence described hereinabove. Although crystals symmetrical about other axes can be found using other faces of the seed crystal (e.g. (110), (111), (113)] to set the growth pattern, diamonds symmetrical about the cube axis yield the most crystal and are of the best quality for a given reaction cell volume during a given growth time. 344 It is an important feature of this invention that the seed crystal sets the growth, pattern for, but does not become part of, the new diamond growth thereby assuring symmetrical growth without having the interior obscured as by the pres5 ence of a seed.

In each of the following Examples 25-29 the reaction vessel configuration provided a temperature differential in the 20-30° C range, the nutrient consisted of 1 part by weight SP-1 graphite and 3 parts by weight 325 mesh diamond ) prepared by the thin film method, seeds used were 1/4 to 1/2 mm and temperatures were measured using a Pt/Pt 10 Kh thermo* couple: EXAMPLE 25 Pressure Temperature (13.3-13.3 mv) Catalyst Nutrient ...56 kb ...1340-1370’C ...Ee + 3 wt.# Al ...500 mgm + 0.05 mg B^C crystal Nucleation Suppressing Layer Isolation Barrier Seed Arrangement Time Weight of Diamond Growth ...None ...I,mil Pt disc as in Fig.19 ...as in Fig. 19 ...165 hours ...287.5 mgm Hie seeded diamond growth was dark blue with the characteristic contrasting crossed bands, or zones, described hereinabove. The high quality crystal had few interior flaws, Ρ phosphoresced to some extent after exposure to 2537 A light and was highly semi-conductive. A second small crystal grew out of the field of growth of the large seeded crystal. The large diamond was a truncated octahedron with modifying cube faces and symmetrical about the cube axis extending parallel to the vertical axis of vessel 30.

EXAMPLE 26 Pressure ...as in Example 25 Temperature (13.2-13.3 mv) ...as in Example 25 ...as in Example 25 ,.

Catalyst Nutrient Nucleation Suppressing Layer ...None Isolation Barrier ...1 mil Pt disc as in Pig.19 Seed Arrangement ...in Pig. 19 Time ...163 2/3 hours Weight of Diamond Growth ...194.7 mgm A single crystal resulted appearing relatively flawfree under 15X magnification. The color was dark blue with a white cross even more distinct than In the diamond produced in Example 25. This crystal also phosphoresced to some extent from all except the bands, which appeared dark and the stone exhibited high semi-conductivity. The diamond was a truncated octahedron with modifying cube faces.

When similar experiments were conducted using a substantially aluminum-free system the seeded crystal growth was ycllow-Grccn. ,,,500 mgm + .05 mgm B isotope EXAMPLE 27 Pressure Temperature (about l4.1 mv) Catalyst ..57 kb .,i42O-i44o° c ..3OEe7ONi containing about 10 ppm Al Niitrient Nucleation Suppressing Layer ...200 mgm. + 2,4 mgm B^C ...5 mil Co disc with 80 mil hole in center Isolation Barrier , Seed Arrangement Time Weight of Diamond Growth ...1/2 mil Pt disc ...Pt covered seed projecting into hole in Co disc ...46 hours ...66.5 mgm One yellow-green diamond crystal grew from the ι diamond seed, an octahedron with small cube faces at points thereof. Boron content was found to be high and non-uniform and the crystal was highly semi-conducting. The crystal evidenced no absorption in the infrared region at 2800 wave lengths cm-4· indicating there was no un-ionized (uncompensated) ι aluminum.

EXAMPLE 28 Pressure Temperature (about 14.1 mv) Catalyst Nutrient Nucleation Suppressing Layer ...as in Example 27 ...as in Example 27 ...as in Example 27 ...200 mgm + 5 mgm B isotope ...5 mil Co disc with 80 mil hole in center EXAMPLE 28 - cont'd Isolation Barrier ···! mil Ft disc Seed Arrangement ...as in Example 27 Time ...78 hours Weight of Diamond Growth ...ll4 mgm One yellow green diamond crystal grew having dark blue-green striations. Boron content (of the order of 500 ppm) was high*but not uniform. The crystal shape, electrical conductivity and IR absorption were as in the product of Example 27.

Yellow-green diamonds found in nature are not semiconducting. Such crystals have the unique combination of size, semi-conductivity, strength and lack of absorption in the radiation band of 3.30 μ - 3·75 Λ· As such these crystals can be used as in-line windows for a high pressure reaction vessel and be used to monitor absorption bands of materials under pressure and an improved voltage. - 67 1344 EXAMPLE 29 Pressure Temperature (13.3-13-4 mv) Catalyst •Nutrient (as in Pig. 5) • Getter Nucleation Suppressing Layer Isolation Barrier Seed Arrangement Time - ,-. ...56 kb ...1360-1380° C ...16.7 Co 41.3 Fe 42 Ni ...120 mgm for layer 57 and 34o mgm for layer 58 ...10 mil disc for Zr ...5 mil Co disc ...1 mil Pt disc ...1/2 mm seed as in Fig. 21 ...about 20 hours Due' to the use of too low a temperature a clustertype growth resulted. Some crystals were colorless, some yellow and a single crystal had a colorless portion adjacent a yellow portion. The initial growth was the yellow color. All diamonds were small, about 1 mm in size.

Gem quality diamonds have been produced in the practice of this invention in near colorless, clear light yellow and clear dark yellow. Colorless is used interchangeably with white or water white. The near colorless crystals are typical truncated octahedra with modifying cube faces while the yellow stones are well-developed octahedra with minor truncations and with one point diminished. The latter shape is excellent for high weight yield when cut as a round brilliant.

The near colorless stones rated H to J on the Gemological Institute of America (GIA) Grading Scale, which has rating values ranging from D (colorless) to N (yellow). Occasional inclusion of catalystsolvent occur in the crystals as removed from the apparatus. but many of these can be cut away in the preparation of a fashioned diamond.

Under 45$ magnification these crystals may display minute white inclusions not visible under the 10X standard magnification used in the grading of diamonds. These minute inclusions do not affect the brilliance of the crystals and are not considered flaws.

The near colorless diamonds grown from a cube face phosphoresce after excitation by ultraviolet light (2537 A) with a characteristic pattern in which a pair of nonv phosphorescing linear bands ln crossed relationship appear in contrast to the balance of the crystal, which phosphoresces. In contrast to those natural diamonds which phosphoresce these near colorless diamonds phosphoresce for a very long time, e.g,, of the order of 1 hour. The phosphorescing diamonds are all low in nitrogen content.

Although all natural stones having a rating of G or lower (progressing toward N) on the GIA Color-Grading System have a large ultraviolet absorption band at about 4155 none of the near colorless H-J rating diamonds prepared according to this Invention displayed such ultraviolet absorption band, i.e., these crystals give a substantially flat response from 2250 λ to greater than 4500 1. This phenomenon makes such stones particularly useful as spectrometer crystals for the monitoring of radiation in tho visible to ultraviolet range.

Further, the colorless diamonds in the H-J range (GIA scale) prepared according to this invention are good semi-conductors, when traces of boron are present. More boron (about 1/4 ppm or more) starts to color crystal blue.

The combination of crystal size (greater than 1/20 carat, · particularly those greater than 1/5 carat), semi-conductivity and near-colorless clarity afforded by these diamonds and not observed in natural diamonds provides an excellent capability for the construction of high pressure vessels for the monitoring of absorption bands of materials subject to the simultaneous application of high pressure and applied voltage. Thus, such large, single-crystal near-colorless diamonds can be used as in-line windows for a high pressure, vessel for making observations during the conduct of high pressure processes Also, apparently because of a) the difference in nitrogen content and b) the manner in which the nitrogen is present, near colorless diamonds produced by the practice of this invention exhibit a much superior thermal conductivity at temperatures in the range of about 10-100°K and abrasion ) resistance for in excess of that found in single crystal natural diamonds submitted to the grinding wheel abrasion test. Nitrogen contents of less than 10A atoms of nitrogen per cm^ (iess than 20 ppm of N) In the diamonds of this invention are particularly effective In increasing both thermal conductivity and abrasion resistance.

Thus, the thermal conductivity of natural diamond did not exceed about 120 watts/cm°K (at 8o°K) while near ' colorless diamond of this invention had a value of l8o watts/ cm°K at the same temperature.

In the grinding wheel abrasion test abrasion resistance quality (grinding ratio) is taken as the volume of corundum (removed from a 6o grit corundum wheel) in cubic inches removed per gram of diamond consumed. . During the test the diamond is oriented with the most resistant grinding direction [the (110) direction on the cube face] against the wheel. During the test the in-feed to the corundum wheel was .001 for each pass. Near colorless diamond according to this invention (less than 20 ppm N content) displayed' grinding ratios ranging from over 32,000.to 20.0,000 in 3/g® of diamond while colorless natural gave grinding ratios ranging from 12,000-64,000 in ^/gm of diamond.

The near-colorless diamonds of this invention do not fluoresce under long wave ultraviolet light (3660 λ). However, under short wave ultraviolet light (2537 A) these diamonds fluoresce strongly in tones of yellow and green.

Therefore, it can be concluded that the low nitrogen content, near colorless (H to J on the GIA Grading Scale) diamonds of this invention are superior to natural diamond for use as heat sinks at cryogenic temperatures and will provide more abrasion-resistant (and thereby more durable) gem stones.

Claims (25)

. CLAIMS

1. A process for the prodtction of diamond material comprising the steps of: pressurizing a reaction vessel containing a diamond seed material and a material comprising a source of carbon or a source of carbon containing an impurity for coloring diamond growth, separated by a mass of material comprising a catalyst-solvent or a catalyst-solvent containing an impurity for coloring diamond growth, to a pressure in the diamond stable region of the phase diagram for carbon; while simultaneously heating said reaction vessel in such a manner that the diamond seed material is at a temperature near the minimum temperature of said region and said source of carbon is at a tempersiure near the maximum temperature of said region, whereby a temperature gradient is created between said seed material and carbon source; characterized by inhibiting diamond growth in at least one of the following group of locations (a) on the diamond seed material until the catalyst-solvent material is saturated with carbon (b) in the vicinity of the diamond seed material and (c) a combination of such locations, under the operating conditions until a substantial diamond growth pattern has been developed from said seed material.

2. A process as defined in Claim 1 wherein said inhibiting step includes the step of suppressing spontaneous nucleation in the vicinity of said seed material. 3. Inert to the reaction vessel and its contents at said operating conditions and having at least one opening in said layer between said diamond seed material and said mass of catalyst-solvent at said operating conditions.

3. A process as defined in Claim 2 wherein said inhibiting step further includes the step of suppressing spontaneous nucleation over a major portion of said seed material while permitting -72diamond growth along a predetermined path. 4. 3 3A-4

4. A process as defined in Claim 3 wherein said inhibiting step further includes isolating said seed material from said catalyst-solvent until said catalyst-solvent is saturated with carbon, whereby erosion of the seed material is prevented. 5. The diamond synthesis mixture includes a component selected from the group consisting of a dopant material, a getter material, a compensator material and a mixture of any of the foregoing materials in an amount at least sufficient to provide the diamond product with a predetermined color, a 5 of catalyst-solvent when said mass is saturated with dissolved carbon. 39. An apparatus as defined in Claim 32 including two different layers in a combination comprising: a. a nucleation suppressing layer substantially 5 a. a nucleation suppressing layer substantially inert to the reaction vessel and its contents at said operating conditions and having at least one opening in said layer between said diamond seed material and said mass of catalyst-solvent at said operating conditions; 5 when in contact with diamond which is higher than the melting point of said mass of catalyst-solvent when said mass is saturated with dissolved carbon.

5. A process as defined in Claim 1 wherein said inhibiting step includes isolating said seed material from said catalystsolvent until said catalyst-solvent is saturated with carbon, whereby erosion of the seed material is prevented.

6. A process as defined in any of Claims 1-5 wherein said seed material is a single crystal.

7. A process as defined in Claims 1-5, wherein said seed material includes a plurality of crystals.

8. A process as defined in any of the preceding claims, wherein the impurity is selected from a dopant material, a getter material, a compensator material and a mixture of any of the foregoing materials in an amount at least sufficient to provide the diamond product with a predetermined color, a color pattern or a zoned coloration.

9. A process as defined in any of the preceding claims, wherein said seed material, carbon source and catalyst solvent are positioned in stacked planar relationship within said reactor vessel, 10. Color pattern or a zoned coloration. 43. An apparatus as defined in Claims 32-41 wherein said diamond seed material is a single crystal. 44. An apparatus as defined in Claim 43 wherein the diamond seed material is oriented with a cube face thereof in 10 inert to the reaction vessel and its contents at said operating conditions and disposed in contact with said mass of catalyst-solvent material; and b. an isolation layer having a melting point when in contact with diamond which is higher 10 b. a nucleation suppressing layer which melts at a temperature higher than said mass of catalyst79 advent and is a material different from said mass; and c. an isolation barrier having a melting point when in contact with diamond which is higher than the melting point of said mass of catalyst-solvent when said mass is saturated with dissolved carbon. 33. An apparatus as defined in Claims 32 wherein said layer is a nucleation suppressing layer substantially inert to the reaction vessel and its contents at said operating conditions and having at least one opening in said layer tetween said diamond seed material and said mass of catalyst-solvent at said operating conditions. 34. An apparatus as defined in Claim 33 wherein the catalyst-solvent material includes at least one small lump extending through an opening in said nucleation suppressing layer to interconnect said mass of said catalyst-solvent material and said diamond seed material. 35- An apparatus as defined in Claim 33 wherein at least one said opening is adapted to comprise a restricted diamond growth path extending through said layer and interconnecting said mass of said catalyst-solvent material and a volume containing said diamond seed material. 36. An apparatus as defined in Claim 35 wherein disposed in said opening is a solid wire of a catalyst-solvent material for the diamond-making reaction. 37. An apparatus as defined in Claims 32 wherein said barrier layer is a nucleation suppressing layer which melts at a temperature higher than said mass of catalyst-solvent and is a 8o 4 3344 material different from said mass. 38. An apparatus as defined in Claim 32 wherein, said layer is an isolation layer having a melting point when in contact with diamond which is higher than the melting point of said mass 10 material different from said mass.

10. A process as defined in Claim 9 wherein said inhibiting step is performed by interposing a barrier layer in the reaction vessel between said diamond seed material and said mass of catalyst-solvent prior to said pressurising and heating steps.

11. A process for the production of diamond material as claimed in Claim 1, characterized in that said process comprises the steps of interposing in the reaction vessel between said diamond seed material and - 73 3 3 4 4 said mass of catalyst-solvent before the reaction vessel is inserted in a means for allying high temperature and high pressure at least one of the following group of barrier layers: a. a nucleation suppressing layer substantially inert to the reaction vessel and its corients at said operating conditions and having at least one opening in said layer between said diamond seed material and said mass of catalyst-solvent at said operating conditions; 0 b, a nucleation suppressing layer which melts at a temperature higher than said mass of catalyst-solvent and is a material different from said mass; and c. an isolation layer having a melting point

12. A process as defined in Claims 11 wherein said layer is a nucleation suppressing barrier layer substantially

13. A process as defined in Claim 12 wherein the catalyst ϊ solvent material includes at least one small lump extending through an opening in said nucleation suppressing barrier lqyer to interconnect said mass of said catalyst-solvent material and said diamond seed material. 74 433 44

14. A process as defined in Claim 12 wherein at least one said opening is adapted to comprise a restricted diamond growth path extending through said barrier and interconnecting said mass of said catalyst-solvent material and a volume containing said diamond seed material. 15. Contact with said barrier layer or the mass of catalystsolvent. 45. A process as claimed in Claim 1 for the production of diamond material substantially as hereinbefore described in any one of the examples. 20 46. Diamond material when produced by a process as claimed in any one of Claims 1 to 22 and Claim 45. 47. An apparatus as claimed in Claim 23 for the production of diamond materials substantially as hereinbefore described in any one of the examples. 15 than the melting point of said mass of catalystsolvent when said mass is saturated with dissolved carbon and which is disposed between said diamond seed material and said mass of catalyst-solvent material. 20 40. An apparatus as defined in Claim 39 wherein said isolation layer is separated from said mass of catalyst-solvent by said nucleation suppressing layer. 41. An apparatus as defined in Claim 40 wherein 81 said nucleation suppressing layer melts at a temperature higher than said mass of catalyst-solvent and is a material different from said mass. 42. An apparatus as defined in Claims 32-41 wherein

15. A process as defined in Claim 14 wherein disposed in said opening is a solid wire of a catalyst-solvent material for the diamond-making reaction.

16. A process as defined in Claims 11 wherein said layer is a nucleation suppressing layer which melts at a temperature higher than said mass of catalyst-solvent and is a material diferent from said mass.

17. A process as defined in Claims li wherein said layer is an isolation layer having a melting point when in contact with diamond which is higher than the melting point of said mass of catalyst-solvent when said mass is saturated with dissolved carbon.

18. A process as defined in Claim 11 wherein two different layers are used in a combination comprising: a. a nucleation suppressing layer substantially inert to the reaction vessel and its contents at said operating conditions and having at least one opening in said layer between said diamond seed material and said mass of catalyst-solvent at said operating conditions and disposed in contact with said mass of catalyst-solvent material; and b. an isolation layer having a malting point when in contact with diamond vijich is higher than tha melting point of said mass of catalyst-solvent when said mass is •13 3 4 4 saturated with dissolved carbon and which is disposed between said diamond seed material and said mass of catalyst-solvent material.

19. A process as defined in Claim 18 wherein said 5 isolation layer is separated from said mass of catalyst solvent by said nucleation suppressing layer.

20. A process as defined in Claim 19 wherein said nucleation suppressing layer melts at a temperature higher than said mass of catalyst-solvent and is a

21. A process as defined in Claims 11-20 wherein said diamond seed material is a single crystal.

22. A process as defined in Claim 21 wherein the diamond seed material is oriented with a cube face thereof in 15 contact with said barrier layer or the mass of catalyst solvent.

23. Apparatus for the production of diamond materials comprising a reaction vessel containing a diamond seed material and a material comprising of a source of carbon or a source of carbon containing an impurity for coloring diamond growth separated by a mass of material comprising a catalyst-solvent or a catalystsolvent containing an impurity for coloring diamond growth; means for pressurizing said vessel to a pressure in the diamond stable region of the phase diagram for carbon; means for heating said vessel, contemporaneously with pressurization, in such a manner that the diamond seed material is at a temperature near the minimum temperature of said region and said source of carbon is at a temperature near the maximum temperature of said region, whereby a temperature gradient is created between said seed material and carbon source; characterized by means interposed between said diamond seed material and catalyst solvent for inhibiting reaction of the catalyst solvent with said seed material and in the peripheral vicinity thereof, under the operating conditions of the diamond making process until a substantial diamond growth pattern has developed from said seed material.

24. An apparatus as defined in Claim 23 wherein said inhibiting means is adapted and arranged to suppress spontaneous nucleation in the vicinity of said seed material. 25 An apparatus as defined in Claim 24 wherein said inhibiting means is adapted and arranged to suppress nucleation over a major portion of said seed material and permit diamond growth along a predetermined path. 77 4 3 3 4 4 26. An apparatus as defined in Claim 25 Tfcdierein said inhibiting means is further means adapted and arranged to isolate said seed material from said catalyst-solvent until said Catalystsolvent is saturated with carbon, whereby erosion of said seed material is prevented. 27. An apparatus as defined in Claim 23 wherein said inhibiting means is adapted and arranged to isolate sal d seed material from said catalyst-solvent until said catalyst-solvent is saturated with carbon, whereby erosion of said seed material is prevented. 28. An apparatus as defined in Claims 23-27 wherein said diamond seed material is a single crystal. 29. An apparatus as defined in Claim 23-28 wherein the impurity is selected from the group consisting of a dopant material, a getter material, a compensator material and a mixture of any of the foregoing materials in an amount at least sufficient to provide the diamond product with a predetermined color, a color pattern or a zoned coloration. 30. An apparatus as defined in Claims 23-29 wherein said seed material, carbon source and catalyst-solvent are arranged in stacked planar relationship within said vessel. 31. An apparatus as defined in Claim 30 wherein said inhibiting means is a barrier layer interposed between said diamond seed material and said catalyst-solvent. 32. An apparatus for the production of diamond material as claimed in Claim 23 wherein 78 a barrier layer in said reaction vessel is interposed between said diamond seed material and said mass of catalyst-solvent, said barrier layer being selected from at least one of the following:

25. 48. Diamond material when produced by apparatus as claimed in any one of Claims 23 to 44 and Claim 47.