DESC:TECHNICAL FIELD
[0001] The present invention generally relates to the technical field of HPHT treatment of diamonds. Particularly, the present disclosure provides an improved diamond holding device that ensures uniform distribution of temperature and pressure.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Superior quality gemstone with rarest natural color like blue, yellow, green, red and pink command very high prices. Even a colorless diamond is considered rare and hence, commands similar price. Because of high value commanded by colorless or colored diamonds, techniques exist to alter a naturally colored diamond to a fancy color, or make it colorless. These techniques include High Pressure High Temperature (HPHT) technique, electron bombarding and annealing process and they are carried out in combination or individually as appropriate. Identification of suitable diamonds for such processes is typically done by infrared absorption spectroscopy, photoluminescence or other chemical analysis. Identification of diamonds for HPHT treatment is art, which cannot be possessed without deep experience and study of color center. Only perfect type 2A diamond can be perfect colorless as per Gemological Institute of America (GIA) certification.
[0004] In 1954, Francis P. Bundy, H.M. Strong, Howard Tracy Hall and others working at General Electric proved that diamond can be made in laboratory. Success in production of man-made diamonds further gave a strong push to HPHT treatment for altering color and properties of both natural diamonds as well as lab grown diamonds. High pressure High Temperature (HPHT) treatment of diamonds typically involves subjecting the diamond(s) to pressures of 5 GPa to 11 GPa and temperatures of 1100°C to 3500°C while holding them in a diamond cell. Once the one or more diamonds (or a batch of diamonds) are held in the diamond cell, the diamond cell is mounted between two faces of a die, which, in turn, is mounted between anvils of a high pressure apparatus such as press. For good results of HPHT treatment, maintenance of correct pressure and temperature conditions are important. Equally important is the uniformity of application of temperature and pressure. Non-uniformity of pressure and/or temperature in the diamond cell may result in damage to the diamond, which being highly priced, incurs huge financial losses.
[0005] Commercially available diamond cells leads to high rate of damage to the diamonds undergoing HPHT treatment, owing to amorphization, graphitization, and/or breakage/fracture of diamonds (due to non-uniformity of pressure distribution). Typically, instances of breakage/fracture of diamonds during the HPHT treatments vary from 3% to as high as 10%, when commercially available (or conventional) diamond cells are used.
[0006] The press used in the HPHT treatment of diamonds may also play a significant role in outcomes of the HPHT treatment. Conventionally, cubic or tetrahedral presses were believed to be better as compared to the torroidal or belt presses (e.g. US8961920B1) for effecting HPHT treatment of diamonds. US8961920B1 teaches that cubic or tetrahedral presses applies pressure on the diamond cell from 6 sides and hence, affords uniformity in application of pressure as compared to the torrodial presses that applies pressure only from top and bottom side.
[0007] Fig. 1 illustrates a conventional cylindrical shaped diamond cell (as disclosed in US7323156B2) that can be used with a cubic press for effecting HPHT treatment of diamonds. The cell of US7323156B2 includes: a hollow cylinder 26; cylinder 28 (a graphite electrical resistance heater tube) positioned concentrically within the salt cylinder 26; a cylindrical salt liner 42 defining radial pressure-transmitting medium layers 43a and 43b, and an axial pair of salt plugs, 44a and 44b defining an axial pressure-transmitting medium layer positioned within the cylinder 28; a pair of conductive-metal end discs 30a and 30b disposed axially with respect to the heater tube 28; end cap assembly 32a and 32b, each of which including an insulating plug 34a and 34b surrounded by an electrically conductive ring 36a and 36b. Positioned between the punches 14 and belt member 16 are a pair of insulating assemblies 18a and 18b, each of which is formed of a pair of thermally- and electrically-insulating members 20 a–b and 22 a–b, with an intermediate metallic gasket, 24a and 24b, disposed therebetween. The diamond cell of US7323156B2, which is generally cylindrical in shape comprising a plurality of inter-fitting cylindrical members, suffers from the major disadvantages that – such diamond cells are not particularly suited for the torroidal and belt presses; and the instances of damage to the diamonds, undergoing the HPHT treatment, are high (around 5%) owing breakage/fracture of diamonds (due to non-uniformity of pressure distribution) when used in torroidal presses. Akin to US7323156B2, EP1272266B1 and US4174380 also discloses cylindrical shaped diamond cells comprising a plurality of inter-fitting cylindrical members, that suffer from the aforesaid shortcomings.
[0008] IN328437 (erstwhile, patent application no. 201921001082), assigned to the Applicant of the instant application, discloses a diamond cell particularly suited for the torroidal press for effecting HPHT treatment of diamonds. However, it suffers from the problem of limited capacity to hold the number of diamonds, while ensuring uniform distribution of temperature and pressure. Particularly, it could be noted that when volume of the diamond cell of IN’437 is increased to accommodate/hold higher number of diamonds therewithin during a HPHT cycle, temperature within the heat transmitting medium (PHT medium, shown as 1 in FIG. 1 of IN’437) holding the diamond, across its volume, does not remain constant during the HPHT cycle, affecting the desired outcome in terms of color and/or quality of the treated diamonds.
[0009] With the popularity of CVD diamonds (lab grown diamonds), demand of the HPHT treatment of diamonds is increasing exponentially. Accordingly, need was felt of diamond cell that has capacity to hold higher number of diamonds as compared to the conventional diamond cells, while ensuring uniform distribution of temperature and pressure. Simply put, the diamond cell should have the capacity sufficient to hold a number of diamonds in a batch such that higher number of diamonds can simultaneously be subjected to the HPHT treatment. The present disclosure particularly addresses this technical problem and solves the long standing need in the state of art.

OBJECTS
[0010] An object of the present disclosure is to provide an improved diamond holding device that overcomes one or more shortcomings of the conventional devices.
[0011] Another object of the present disclosure is to provide an improved diamond holding device that has capacity to hold higher number of diamonds as compared to the conventional diamond cells, while ensuring uniform distribution of temperature and pressure.
[0012] Further object of the present disclosure is to provide an improved diamond holding device that reduces manufacturing and assembling time.
[0013] Still further object of the present disclosure is to provide an improved diamond holding device that reduces the radiation and thermal loss and in turn aid in reducing the heating time, while affording uniform distribution of temperature.

SUMMARY
[0014] The present invention generally relates to the technical field of HPHT treatment of diamonds. Particularly, the present disclosure provides an improved diamond holding device that ensures uniform distribution of temperature and pressure.
[0015] An aspect of the present disclosure provides a diamond holding device for high pressure high temperature (HPHT) treatment of diamonds. The device includes: an outer body with a hole; a pair of conductive plates adapted to be received within the hole; an assembly including a heat generating cylindrical member backed by a heat refracting cylindrical member and a pair of first plates, said assembly defining a cavity for receiving a pressure and heat transmitting (PHT) medium with one or more diamonds embedded therewithin, and said pair of first plates covering top and bottom surfaces of the cavity; a pair of insulating plates configured to be received in the hole, each of the insulating plates defines a convex outer surface and defines a bore for receiving a conductive plug therein. In an embodiment, the device is of hemispherical shell type shape.
[0016] In an embodiment, the outer body is made of a soft material such as pyrophyllite, limestone or alumina. In an embodiment, the conductive plates are made of a material having low electrical resistance such as graphite flakes. In an embodiment, the heat generating cylindrical member is made of a material having high resistance, such as graphite, such that it generates heat upon passage of electricity. In an embodiment, the heat refracting cylindrical member is made of an insulating material such as salts (e.g. chloride, bromide or iodide salt of sodium, cesium or potassium), zirconia, graphite or mixture thereof. In an embodiment, the heat generating cylindrical member is configured to be slidably received in the heat refracting cylindrical member. In an embodiment, the first plates are made of a refractory material such as salts (e.g. chloride, bromide or iodide salt of sodium, calcium, cesium or potassium), zirconia, graphite or mixture thereof. In an embodiment, the insulating plates are made of a refractory material such as salts (e.g. chloride, bromide or iodide salt of sodium, calcium, cesium or potassium), zirconia, graphite or mixture thereof. In an embodiment, the conductive plugs are made of a material having low electrical resistance such as graphite flakes.
[0017] In an embodiment, the pair of insulating plates affords transmission of pressure put on them to the PHT medium via the pair of conductive plates and the pair of first plates. In an embodiment, the pair of conductive plugs affords transmission of the electricity to the heat generating cylindrical member via the pair of conductive plates, such that the heat generating cylindrical member generates heat.

BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 illustrates an exemplary schematic view of the conventional diamond holding device.
[0019] FIG. 2A-2G illustrate exemplary cross-sectional views of the diamond holding device, realized in accordance with embodiments of the present disclosure.
[0020] FIG. 2H illustrates an exemplary schematic showing flow path of electricity and heating area in the diamond holding device realized in accordance with an embodiment of the present disclosure.
[0021] FIG. 3 illustrates an exemplary cross-sectional view of the diamond holding device positioned in the torroidal press, in accordance with an embodiment of the present disclosure.
[0022] FIG. 4A and 4B illustrate exemplary cross-sectional views of torroidal die, realized in accordance with embodiments of the present disclosure.
[0023] FIG. 5 illustrates an exemplary cross-sectional view of a torroidal die, realized in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0024] The present invention generally relates to the technical field of sequencing and diagnostics. Particularly, the present disclosure provides an adaptive sequencing device that may find utility in transferring samples across different devices reducing the human intervention and hence, aids in reducing errors.
[0025] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0026] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0027] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0028] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0029] An aspect of the present disclosure provides a diamond holding device for high pressure high temperature (HPHT) treatment of diamonds. The device includes: an outer body with a hole; a pair of conductive plates adapted to be received within the hole; an assembly including a heat generating cylindrical member backed by a heat refracting cylindrical member and a pair of first plates, said assembly defining a cavity for receiving a pressure and heat transmitting (PHT) medium with one or more diamonds embedded therewithin, and said pair of first plates covering top and bottom surfaces of the cavity; a pair of insulating plates configured to be received in the hole, each of the insulating plates defines a convex outer surface and defines a bore for receiving a conductive plug therein. In an embodiment, the device is of hemispherical shell type shape.
[0030] In an embodiment, the outer body is made of a soft material such as pyrophyllite, limestone or alumina. In an embodiment, the conductive plates are made of a material having low electrical resistance such as graphite flakes. In an embodiment, the heat generating cylindrical member is made of a material having high resistance, such as graphite, such that it generates heat upon passage of electricity. In an embodiment, the heat refracting cylindrical member is made of an insulating material such as salts (e.g. chloride, bromide or iodide salt of sodium, cesium or potassium), zirconia, graphite or mixture thereof. In an embodiment, the heat generating cylindrical member is configured to be slidably received in the heat refracting cylindrical member. In an embodiment, the first plates are made of a refractory material such as salts (e.g. chloride, bromide or iodide salt of sodium, calcium, cesium or potassium), zirconia, graphite or mixture thereof. In an embodiment, the insulating plates are made of a refractory material such as salts (e.g. chloride, bromide or iodide salt of sodium, calcium, cesium or potassium), zirconia, graphite or mixture thereof. In an embodiment, the conductive plugs are made of a material having low electrical resistance such as graphite flakes.
[0031] In an embodiment, the pair of insulating plates affords transmission of pressure put on them to the PHT medium via the pair of conductive plates and the pair of first plates. In an embodiment, the pair of conductive plugs affords transmission of the electricity to the heat generating cylindrical member via the pair of conductive plates, such that the heat generating cylindrical member generates heat.
[0032] FIG. 2A illustrates an exemplary cross-sectional view of the diamond holding device for high pressure high temperature (HPHT) treatment of diamonds. As can be seen from FIG. 2A, the device includes: an outer body (3) with a hole; a pair of conductive plates (9) adapted to be received within the hole; an assembly (12) including a heat generating cylindrical member (8) backed by a heat refracting cylindrical member (4) and a pair of first plates (10), said assembly (12) defining a cavity (13) for receiving a pressure and heat transmitting (PHT) medium (11) with one or more diamonds embedded therewithin, and said pair of first plates (10) covering top and bottom surfaces of the cavity; a pair of insulating plates (5) configured to be received in the hole, each of the insulating plates defines a convex outer surface and defines a bore for receiving a conductive plug (6) therein. As can also be seen from FIG. 2A, the device is of hemispherical shell type shape affording uniform distribution of pressure, and hence, significantly reduces the instances of breakage/fracture of diamonds undergoing HPHT treatment.
[0033] The outer body (3) can be made of a soft material such as pyrophyllite, limestone or alumina, but not limited thereto. The conductive plates (9) are made of a material having low electrical resistance such as graphite flakes. The heat generating cylindrical member (8) can be made of a material having high resistance, such as graphite, but not limited thereto, such that it generates heat upon passage of electricity. The heat refracting cylindrical member (4) can be made of an insulating material such as salts (e.g. chloride, bromide or iodide salt of sodium, cesium or potassium), zirconia, graphite or mixture thereof, but not limited thereto. The heat generating cylindrical member (8) can be configured to be slidably received, longitudinally, within inner circumference of the heat refracting cylindrical member (4). The first plates (10) can be made of a refractory material such as salts (e.g. chloride, bromide or iodide salt of sodium, calcium, cesium or potassium), zirconia, graphite or mixture thereof, but not limited thereto. The insulating plates (5) can be made of a refractory material such as salts (e.g. chloride, bromide or iodide salt of sodium, calcium, cesium or potassium), zirconia, graphite or mixture thereof, but not limited thereto. The conductive plugs (6) can be made of a material having low electrical resistance such as graphite flakes.
[0034] The PHT medium (11) can include graphite or material(s) having high resistance or such other materials, as known to or appreciated by a person skilled in the art. In an embodiment, one or more diamonds to be subjected to the HPHT treatment are placed in the PHT medium (such as graphite powder of high resistance), and pressed to form a block with diamonds embedded therewithin. The PHT medium along with the diamonds can then be placed within the assembly (12). The cavity is then closed by placing the first plates (10) on the top and bottom surfaces. As can also be seen from FIG. 2A-2F, the heat generating cylindrical member (8) defines side walls of the cavity and the pair of first plates (10) defines top and bottom walls of the cavity such that the PHT medium (with one or more diamonds embedded therewithin) can be held within the cavity (13). Preferably, profiles of the heat generating cylindrical member (8) and/or the pair of first plates (10) are such that the first plates (10) can be snugly fitted within the inner circumference of the heat generating cylindrical member (8), securely holding the PHT medium (11) within the cavity (13).
[0035] The pair of insulating plates (5) affords transmission of pressure put on them to the PHT medium (11) via the pair of conductive plates (9) and the pair of first plates (10). The pair of conductive plugs (6) affords transmission of the electricity to the heat generating cylindrical member (8) via the pair of conductive plates (9), such that the heat generating cylindrical member (8) generates heat. In embodiments where the PHT medium is made of or includes the material of high resistance, the PHT medium also generates heat.
[0036] FIG. 2B illustrates an exemplary sectional view of a variation of the diamond holding device shown in FIG. 2A, for high pressure high temperature (HPHT) treatment of diamonds. As can be seen from FIG. 2B, the outer body (3) defines a collar (3a) that, when the diamond holding device (100) is positioned/put in the center portion (24) of the matrix (20 shown in FIG. 4), extends from the center portion (24, shown in FIG. 4) to the groove (22, shown in FIG. 4). The skilled artisan would readily appreciate that in this configuration, the toroidal ring (21) need not define the collar portion. In an alternative embodiment, the collar (3a) extends from the center portion (24, shown in FIG. 4) partially towards the groove (22, shown in FIG. 4). In such configuration, both the outer body (3) and the toroidal ring (21) define the collar portions so as to occupy the region/space extending between the center portion (24, shown in FIG. 4) and the groove (22, shown in FIG. 4).
[0037] FIG. 2C illustrates an exemplary cross-sectional view of a variation of the diamond holding device shown in FIG. 2A, for high pressure high temperature (HPHT) treatment of diamonds. As can be seen from FIG. 2C, the outer body (3) defines a collar portion (3a) and a toroidal portion (3b) such that when the diamond holding device (100) is positioned/put in the center portion (24) of the matrix (20 shown in FIG. 4), the collar portion (3a) extends from the center portion (24, shown in FIG. 4) to the groove (22, shown in FIG. 4) and the toroidal portion (3b) is positioned in the groove (22, shown in FIG. 4). The skilled artisan would readily appreciate that in this configuration, the toroidal ring (21) need not be used, when a toroidal die with a single toroidal groove is used (as shown in FIG. 5).
[0038] FIG. 2D illustrates an exemplary cross-sectional view of another variation of the diamond holding device for high pressure high temperature (HPHT) treatment of diamonds shown in FIG. 2A. As can be seen from FIG. 2D, each of the insulating plates (5) are of flat outer surface (i.e. the surface opposite to the surface facing the conductive plate 9 is of flat shaped), as opposed to the convex outer shape illustrated in FIGs. 2A and 2B. Further, the outer body (3) defines a tapered outer surface (3t) as can also be seen from FIG. 2D. Such configuration is particularly suitable for matrix (i.e. Tc Matrix) of annular shape. One skilled in the art would appreciate that in some cases, one may be inclined to use the matrix of annular shape/profile (instead of hemispherical shaped matrix) owing to limitations as to providing hemispherical shapes on very hard Tc matrix. Construction of annular shaped Tc matrix is explained in detail in granted application SU834983A1, contents whereof are incorporated herein in its entirety, by way of reference.
[0039] FIG. 2E illustrates an exemplary cross-sectional view of a variation of the diamond holding device (100) shown in FIG. 2D, for high pressure high temperature (HPHT) treatment of diamonds. As can be seen from FIG. 2E, the outer body (3) defines a collar (3a) that extends from the center portion (24, shown in FIG. 4) to the groove (22, shown in FIG. 4), occupying the region/space between the center portion and the groove when the diamond container holding device is positioned/put in the center portion (20) of the matrix (20). In this configuration, the toroidal ring (21) need not define the collar portion. In an alternative embodiment, the outer body (3) defines a collar portion (3a) that extends from the center portion (24, shown in FIG. 4) partially towards the groove (22, shown in FIG. 4). In such configuration, both the outer body (3) and the toroidal ring (21) define the collar portions (3a, 21a) so as to occupy the region/space between the center portion (24, shown in FIG. 4) and the groove (22, shown in FIG. 4).
[0040] FIG. 2F illustrates an exemplary cross-sectional view of a variation of the diamond holding device (100) shown in FIG. 2D, for high pressure high temperature (HPHT) treatment of diamonds. As can be seen from FIG. 2F, the outer body (3) defines a collar (3a) a toroidal portion (3b) such that when the diamond holding device (100) is positioned/put in the center portion (24) of the matrix (20 shown in FIG. 4), the collar portion (3a) extends from the center portion (24, shown in FIG. 4) to the groove (22, shown in FIG. 4) and the toroidal portion (3b) is positioned in the groove (22, shown in FIG. 4). The skilled artisan would readily appreciate that in this configuration, the toroidal ring (21) need not be used.
[0041] FIG. 2G illustrates an exemplary cross-sectional view of a variation of the diamond holding device (100) shown in FIG. 2A, for high pressure high temperature (HPHT) treatment of diamonds. As can be seen from FIG. 2G, the heat generating cylindrical member (8) includes a wave shaped cylindrical heating member (8a) defining a plurality of peaks (8p) and troughs (8t). The heating member (8a) can be made of a suitable metal(s)/alloys such that they can generate heat. Alternatively, the heating member (8a) can be made of a material having high resistance, such as graphite, such that it acts as a heat generating mechanism. Sometimes sintered heating member may be prone to breakage during assembly due to more weight and less thickness. In such case, it is suitable to employ heating member (8a) made of metal(s)/alloy(s).
[0042] In an embodiment, the wave shaped cylindrical heating member (8a) is embedded in a material having high resistance such that both the member (8a) and the material generate heat upon passage of electricity. In an embodiment, the material within which the heating member (8a) is embedded is different from the material of construction of the wave shaped cylindrical heating member (8a). In an embodiment, the material includes graphite and the wave shaped cylindrical heating member (8a) is made of a metal, an alloy or a mixture thereof.
[0043] FIG. 2H illustrates an exemplary schematic showing flow path of electricity/current and the heating area. As can be seen from FIG. 2H, electricity passes through 6-9-8-9-6 and maximum heat is generated around the PHT medium 11 by the heating member (8) and the PHT medium is heated through conduction of heat from the heating member (8).
[0044] As illustrated in FIG. 3, diamond cell/diamond holding device as described above can be held in a toroidal die assembly comprising two identical faces configured to be opposite to each other, using which diamond cell can be subjected to appropriate pressure. Each face can, in turn, be made of a number of sub-components /matrices that are further described. In FIG. 3 the parts are identically labelled, adding “a” for such a component on one face, and “b” for a similar component configured on the opposite face.
[0045] Toroidal die assembly can have a block (that can be interchangeably termed as matrix or block matrix) shown as (X) in turn having a block/matrix (20) via which high pressure can be transmitted from the toroidal die assembly to the diamond cell. Matrix 20 can be surrounded by concentric rings shown as internal ring (19), intermediate ring (18) and outside ring (17) made of mild steel that can serve as support to matrix 20 due to their high tensile strength. Matrix 20 can be made of tungsten carbide (Tc) and it helps in maintaining proper pressure on the diamond cell. The construction of matrix 20 is elaborated in FIGs. 4 and 5.
[0046] Block matrix X can be held/attached (on both sides of the toroidal die assembly) on a support plate (shown as Y) that can transfer pressure and also remove unwanted heat from the block matrix X. Support plate Y can have an insert (16) for transferring high pressure to block matrix X. Insert 16 can be surrounded by fastening ring (15) that can in turn be surrounded by external ring (14). These rings can serve as support to insert 16 due to their high tensile strength. A refrigerating coil (13) can be mounted around ring 14 to remove unwanted heat from block matrix X. The rings can be made of mild steel.
[0047] Support plate Y can, in turn, be held/attached (on both sides of the toroidal die) to a backing plate (shown as Z) that can enable pressure transfer to support plate Y. Backing plate Z can have insert (shown as 12) for transferring high pressure to support plate Y. Body (11) can hold/support insert 12 due to its high tensile strength. Backing plate Z can, in turn, be held/attached (on both sides of the toroidal die) to a base plate (shown as 10) that can be used for transferring and holding pressure on to backing plate Z.
[0048] As can be readily understood, blocks, matrices, inserts etc. as elaborated above can be made of any suitable material to fulfill their purpose, and can be shaped accordingly. Some of such components (for instance inserts) may not be needed if their function may, as well, be done by the blocks in which they are configured. Rings can, as well, be of cylindrical or any other suitable shape(s).
[0049] As illustrated, the diamond cell can be held in appropriate space (shown as 24 in FIGs. 4A, 4B and 5 further elaborated) configured in matrix 20, and surrounded by one/more toroid rings (toroidal belts) held in grooves configured in matrix 20. One such ring is shown as 21 in FIG. 3. Such ring can be made of, for example, limestone powder and bonding material(s) like backlite. The rings can enclose those surfaces of diamond cell that are not directly receiving pressure from block matrix X and hence, can help retain pressure in the diamond cell.
[0050] FIGs. 4A, 4B and 5 illustrate exemplary cross-sectional views of various configurations of a torroidal die (alternatively and synonymously termed as “Tc matrix”) in accordance with exemplary embodiments of the present disclosure. As already detailed above, Tc matrix 20 (20a being on one face of the die, the opposite face having 20b) is used for transferring high pressure to diamond cell. In an exemplary embodiment, Tc matrix 20 can be of single toroid type having only one toroidal groove (shown as 25 in FIG. 5) and one center portion (shown as 24 in FIG. 5). A toroidal ring (such as ring 21 shown in FIG. 3) can be held in toroidal groove 25, while diamond container (as elaborated in FIG. 2) can be held in center portion 24. The toroidal ring/belt helps to hold pressure and make equivalent balance between upper and lower Tc die matrix. In another exemplary embodiment, a double toroidal matrix as shown in FIG. 4 can be used for ultra-high pressure holding of diamond container. In such a matrix, shown as 20 (20a being one side and 20b the opposite) in FIG. 4, two toroidal grooves shown as 22 and 23 can be configured around a center portion shown as 24. As before, grooves 22 and 23 can each contain toroidal rings/belts while center portion 24 can hold diamond holding device/diamond cell.
[0051] In operation, the diamond container as described above can be placed inside toroidal die assembly and surrounded by toroidal ring (in case the outer body of the diamond holding device includes the toroidal portion, the toroidal ring may be precluded). The diamond container supported by tungsten carbide die can be exposed to high pressure. Pressure of 5 GPa to 11GPa and temperature of 1200 degrees centigrade (Deg C) to 3500 degrees centigrade (Deg C) is created. The temperature should be below graphitization line according to relative pressure from Simon-Berman line of diamond stable region. Such high pressure high temperature (HPHT) treatment is given to diamond held in the diamond container for adequate time to improve the diamond. Process parameter can be selected from the above range or any other range, depending upon nature of defect in the diamond, to change or remove the color of the diamond. Skills and experience in the field can help identify such parameters without excessive experimentation.
[0052] Container as made above can be placed inside the toroidal die assembly or toroidal belt die assembly as described. A pressure 100% of the pre-determined pressure can be achieved and kept constant for a pre-determined time. During this time, initially 60-80% of a target/pre-determined temperature can be achieved and maintained for 2 to 5 minutes in a first stage, and then maintained constant for next 10 seconds to one hour (20 seconds to 5 minutes, for instance). After completion of the first pre-determined time, pressure can be slowly brought to atmospheric pressure in 4 to 8 minutes. During this period of 10 seconds to one hour, electricity is passed through the diamond container thereby generating temperature in the diamond container and annealing the diamond held therein. Thereafter, the HPHT treated diamond container can be removed from the toroidal die assembly and diamond(s) can be recovered by removing surrounding rings etc. by hammering on them. Diamond(s), after HPHT treatment, can have etch marks carrying graphite on its surface. Such marks can be removed by digesting/treating the diamond(s), at a high temperature, with a mixture of sulphuric acid and nitric acid.
[0053] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art. Particularly, in several embodiments of the present disclosure, construction of the diamond cell is explained using rings, plates and cylinders, however, it should be appreciate that any other suitable shapes can be likewise devised. For instance, rings can be substituted by cylinders or concentric spheres holding/comprising various materials as elaborated below, or concentric cubes can be made of various materials as elaborated above, or a combination of spheres and cubes can be used. Similarly, cylinders/cylindrical members can be substituted by rings or plates. All such embodiments and shapes are fully a part of the present disclosure.
[0054] As used herein, and unless the context dictates otherwise, the term “coupled to” is intended to include both direct coupling (in which two elements that are coupled to each other or in contact with each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms “coupled to” and “coupled with” are used synonymously.
[0055] Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C ….and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.
[0056] While some embodiments of the present disclosure have been illustrated and described, those are completely exemplary in nature. The disclosure is not limited to the embodiments as elaborated herein only and it would be apparent to those skilled in the art that numerous modifications besides those already described are possible without departing from the inventive concepts herein. All such modifications, changes, variations, substitutions, and equivalents are completely within the scope of the present disclosure. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims.
EXAMPLES
[0057] DIAMOND HOLDING DEVICE
[0058] A diamond holding device as shown in FIG. 2A was prepared as follows: outer body (3) was prepared from pyrophyllite block using machining process; cylindrical member (4) was prepared using mixture of cesium chloride in an amount of 95% by weight and graphite (99.99% purity grade) in an amount of 5% by weight by press forming; insulating plates (5) was prepared using mixture of cesium chloride in an amount of 95% by weight and graphite (99.99% purity grade) in an amount of 5% by weight by press forming; conductive plugs (6) were prepared using natural graphite flakes by press forming; conductive plates (9) were prepared by cutting them from commercially available electrically conductive graphite sheet; heat generating cylindrical member (8) was prepared using stabilized zirconium oxide powder; outer ring (7) was prepared using mixture of cesium chloride in an amount of 95% by weight and graphite (99.99% purity grade) in an amount of 5% by weight by press forming; and inner plate (10) was prepared using mixture of cesium chloride in an amount of 95% by weight and graphite (99.99% purity grade) in an amount of 5% by weight by press forming. Synthetic graphite powder (99.95% purity grade) was used as PHT medium, and diamond (or a batch of diamonds) were placed in the synthetic graphite powder and pressed in a pressing machine.
[0059] For assembling the diamond holding device, insulating plate (5) with conductive plug (6) fitted therewith was slid within the inner circumference of hole defined in the outer body (3); conductive plate (9) was then slid within the inner circumference of hole defined in the outer body (3); then the cylindrical member (4) was placed in the hole defined in the outer body (3); heat generating cylindrical member (8) was then received within inner circumference of the cylindrical member (4); and first plate (10) was then put within the inner circumference of heat generating cylindrical member (8); the diamond (or a batch of diamonds) embedded in the PHT medium (11, as prepared above) was then placed on the first plate (10); another first plate (10) was then put on top of the PHT medium within the inner circumference of heat generating cylindrical member (8); conductive plate (9) was then slid within the inner circumference of hole and insulating plate (5) with conductive plug (6) fitted therewith was then slid within the inner circumference of hole defined in the outer body (3) to realize the diamond holding device as shown in FIG. 2A, ready to be put in the toroidal die assembly.
[0060] EXAMPLE 1
[0061] 75 natural diamonds of total weight 20.31ct of brown, light brown and dark brown colors were embedded in a graphite cell (PHT medium) and placed inside the diamond holding device. The diamond holding device surrounded by a toroidal ring was placed in the HPHT press. In this experiment, the diamonds were subjected to HPHT treatment at around 2000°C temperature and at 7 GPa pressure for 3 minutes and 30 seconds. After HPHT treatment, the diamonds were removed from the diamond holding device and boiled to remove the extra material around the diamonds. The diamonds were then polished. Polished diamonds were found to be of G to H color, fancy yellow, fancy greenish yellow, fancy orangish yellow color of GIA certificate. Similar results were achieved (in terms of uniformity) when diamond holding device, as shown in Fig. 2D was used. This experiment established that the diamond holding device of the present disclosure is suitable when higher volume of diamonds is to be subjected to HPHT treatment for changing their color.
[0062] EXAMPLE 2
[0063] In this experiment, diamond holding device as shown in FIG. 2C was used. Five CVD diamonds of size 2.88ct, 3.55ct, 3.75ct, 2.89ct, 2.68ct, light brown in color and VS2 grade clarity were embedded in the graphite cell (PHT medium) and placed inside the diamond holding device. As the outer body of the diamond holding device had the toroidal portion, toroidal ring was not positioned/used. In this experiment, the diamonds were subjected to HPHT treatment at around 1900°C temperature and at 6.5GPa pressure for 3 minutes. After HPHT treatment, the diamonds were removed from the diamond holding device and after acid boil of diamonds, the extra material around the diamonds was removed. The diamonds were then polished. Polished diamonds were of F to G color of IGI certificate. It could be noted that when using the diamond holding device as shown in FIG. 2C, the time required for manufacturing various components and in assembling them was low, while ensuring uniformity in HPHT treatment of diamonds due to uniform distribution of temperature and pressure inside the device.

ADVANTAGES
[0064] The present disclosure provides an improved diamond holding device that overcomes one or more shortcomings of the conventional devices.
[0065] The present disclosure provides an improved diamond holding device that has capacity to hold higher number of diamonds as compared to the conventional diamond cells, while ensuring uniform distribution of temperature and pressure.
[0066] The present disclosure provides an improved diamond holding device that reduces manufacturing and assembling time.
[0067] The present disclosure provides an improved diamond holding device that reduces the radiation and thermal loss and in turn aid in reducing the heating time, while affording uniform distribution of temperature.

,CLAIMS:1. A diamond holding device (100) for high pressure high temperature (HPHT) treatment of diamonds, the device comprising:
an outer body (3) with a hole;
a pair of conductive plates (9) adapted to be received within the hole;
an assembly (12) comprising a heat generating cylindrical member (8) backed by a heat refracting cylindrical member (4) and a pair of first plates (10), said assembly (12) defining a cavity (13) for receiving a pressure and heat transmitting (PHT) medium (11) with one or more diamonds embedded therewithin, said pair of first plates (10) covering top and bottom surfaces of the cavity; and
a pair of insulating plates (5) configured to be received in the hole, each of the insulating plates defining a bore for receiving a conductive plug (6) therein.

2. The device as claimed in claim 1, wherein the outer body (3) is made of a soft material including pyrophyllite, limestone and alumina, and wherein conductive plates (9) are made of a material having low electrical resistance.

3. The device as claimed in claim 1, wherein the heat generating cylindrical member (8) is made of a material having high resistance such that it generates heat upon passage of electricity, and wherein the heat refracting cylindrical member (4) is made of an insulating material.

4. The device as claimed in claim 1, wherein the heat generating cylindrical member (8) is configured to be slidably received, longitudinally, within inner circumference of the heat refracting cylindrical member (4).

5. The device as claimed in claim 1, wherein the first plates (10) are made of a refractory material, and wherein the insulating plates (5) are made of a refractory material, further wherein the conductive plugs (6) are made of a material having low electrical resistance.

6. The device as claimed in claim 1, wherein profile of any or a combination of the heat generating cylindrical member (8) and the pair of first plates (10) is such that the first plates (10) are snugly fitted within the inner circumference of the heat generating cylindrical member (8), securely holding the PHT medium (11) within the cavity (13).

7. The device as claimed in claim 1, wherein the pair of insulating plates (5) affords transmission of pressure put on them to the PHT medium (11) via the pair of conductive plates (9) and the pair of first plates (10).

8. The device as claimed in claim 1, wherein the pair of conductive plugs (6) affords transmission of the electricity to the heat generating cylindrical member (8) via the pair of conductive plates (9), such that the heat generating cylindrical member (8) generates heat.

9. The device as claimed in claim 1, wherein the outer body (3) defines a collar portion (3a).

10. The device as claimed in claim 1, wherein the outer body (3) defines a collar portion (3a) and a toroidal portion (3b).

11. The device as claimed in claim 1, wherein the insulating plates (5) are of convex outer surface, and wherein the device is of hemispherical shell type.

12. The device as claimed in claim 1, wherein the outer body (3) defines a tapered outer surface (3t).

13. The device as claimed in claim 1, wherein the insulating plates (5) are of flat outer surface.

14. The device as claimed in claim 1, wherein the heat generating cylindrical member (8) comprises a wave shaped cylindrical heating member (8a) defining a plurality of peaks (8p) and troughs (8t).

15. The device as claimed in claim 1, wherein the wave shaped cylindrical heating member (8a) is embedded in a material having high resistance such that it generates heat upon passage of electricity, said material being different from material of construction of said wave shaped cylindrical heating member (8a).