Method for stabilizing diamond using liquid metal

Abstract

This specification discloses a method for stabilizing diamonds using liquid metals. In one aspect, the process of the present invention has the advantage of preventing graphitization of the diamond surface region through heat treatment for stabilization of diamonds using Ga-based, Sn-based, or In-based liquid metals, and enabling the improvement of diamond color and selective separation of nanodiamonds without reprocessing.

Description

Technology Field

[0001] In this specification, a method for stabilizing diamond using liquid metal is disclosed. Background Technology

[0002] Diamonds are composed of carbon atoms and are allotropes of graphite, but they are bonded via sp³ bonds. Due to this, they possess the highest hardness and have been used as gemstones or for industrial purposes. Natural diamonds have been found on the Earth's surface for approximately 1,000 years; they were formed in a high-temperature and high-pressure environment in the lower mantle, about 200 km underground, and then transported to the surface by volcanic activity. While humanity mines and utilizes these diamonds, the destruction of the natural environment by damaging the Earth's surface during the mining process continues.

[0003] In 1956, the first synthetic diamond was produced by recreating a high-temperature and high-pressure environment in a laboratory. Since then, technology for producing colorless diamonds for jewelry has advanced, and in 2019, it was reported that it was possible to manufacture loose gemstone diamonds weighing over 10 carats. In the early 2000s, technology was introduced to simultaneously grow multiple carat-sized gemstone diamonds using the Microwave Plasma Chemical Vapor Deposition (MP CVD) process. Through this, attempts are being made to produce multiple gemstone diamonds or to create single-crystal diamonds with a diameter of over 2 inches to utilize as substrates for power semiconductors.

[0004] Nanodiamonds are produced by using an explosive method in which explosives such as RDX (Research Department Explosive) and TNT (Trinitrotoluene) are placed in a sealed pressure vessel and instantaneously created to a high temperature and high pressure state. The nanodiamonds produced in this way, with a diameter of about 30 nm, are industrially utilized after graphite impurities are removed. In the case of nanodiamonds, selective treatment using a water-based method or an oxidizing agent is required to remove approximately 70% of the nanographite after explosion, but there is a disadvantage in that the sorting process requires a lot of time and cost due to the nano size. Diamonds produced by the high-temperature and high-pressure method present a problem in that nitrogen is incorporated into the catalyst without special treatment, leading to the formation of color centers associated with various nitrogen impurities and making it difficult to manufacture colorless diamonds. To address this, nitrogen-removing getters such as Al and Ti are added to the catalyst to eliminate nitrogen, or additional high-temperature and high-pressure treatments are performed to convert nitrogen-containing diamonds into specific colors. However, this process causes graphitization on the surface, requiring a re-polishing process to remove it, which results in a decrease in weight.

[0005] Even in the diamond growth process utilizing MP CVD, brown or gray diamonds are frequently produced when a diamond of the desired thickness grows from a seed due to stress or minute nitrogen incorporation. Although high-temperature and high-pressure heat treatment or high-temperature and low-pressure heat treatment within the CVD equipment is performed to convert them to colorless, graphitization occurs on the surface, leading to a problem where the weight of the final product decreases due to the regloss required to remove it.

[0006] Accordingly, the inventors have completed the present invention by developing a process using a Ga-based alloy that effectively removes graphite generated on the surface during high-temperature, high-pressure or high-temperature, low-pressure treatment of conventional diamonds, prevents the generation of graphite during the process, and stably maintains the diamond state even at atmospheric pressure. The problem to be solved

[0007] To control NV (Nitrogen-Vacancy), H3, and N3 color centers in conventional diamonds, graphitization of the diamond surface must be considered, which presented the problem of having to physically remove the graphitized surface layer at the cost of weight loss. Additionally, in the case of nanodiamonds, there was a problem with the difficulty of separating them from residual nanographite.

[0008] Accordingly, one objective of the present invention is to provide a method for stabilizing diamond by using a liquid metal to suppress or prevent the formation of graphite on the diamond surface, and another objective of the present invention is to provide a method for purifying nanodiamonds using a liquid metal. means of solving the problem

[0010] In order to achieve the above objective,

[0011] In one aspect, the present invention provides a diamond stabilization method comprising the steps of: mixing diamond with one or more selected from the group consisting of gallium (Ga)-based alloys, tin (Sn)-based alloys and indium (In)-based alloys, and heat-treating the mixture to produce a liquid metal; and separating the diamond from the liquid metal.

[0012] In an exemplary embodiment, the gallium (Ga)-based alloy may comprise one or more elements selected from gallium (Ga) and tin (Sn), indium (In), bismuth (Bi), nickel (Ni), iron (Fe), silicon (Si), cobalt (Co) and germanium (Ge).

[0013] In an exemplary embodiment, the tin (Sn)-based alloy may comprise one or more elements selected from tin (Sn, Tin); and gallium (Ga, Gallium), indium (In, Indium), bismuth (Bi, Bismuth), nickel (Ni, Nickel), iron (Fe, Iron), silicon (Si, Silicon), cobalt (Co, Cobalt), and germanium (Ge, Germanium).

[0014] In an exemplary embodiment, the indium (In)-based alloy may comprise indium (In) and one or more elements selected from gallium (Ga), tin (Sn), bismuth (Bi), nickel (Ni), iron (Fe), silicon (Si), cobalt (Co) and germanium (Ge).

[0015] In another aspect, the present invention provides a method for purifying nanodiamonds, comprising the steps of: mixing nanodiamonds with one or more selected from the group consisting of gallium (Ga)-based alloys, tin (Sn)-based alloys, and indium (In)-based alloys, and heat-treating the mixture to produce a liquid metal; and separating nanodiamonds from the liquid metal.

[0016] In another aspect, the present invention provides a composition for purifying diamond or nanodiamond comprising one or more selected from the group consisting of gallium (Ga)-based alloys, tin (Sn)-based alloys, and indium (In)-based alloys. Effects of the invention

[0017] In one aspect, the process of the present invention enables the prevention of graphitization on the diamond surface through stabilization heat treatment using Ga-based, Sn-based, or In-based liquid metals. For example, by immersing a single-crystal diamond in a Ga-based, Sn-based, or In-based liquid metal and heat-treating it, it is possible to improve the diamond color without graphitization on the diamond surface or reprocessing. This is applicable to both natural and synthetic diamonds.

[0018] In another aspect, the process of the invention can maintain the stability of diamond even in a vacuum state rather than a hydrogen environment.

[0019] In another aspect, the process of the present invention has the advantage of enabling the selective separation of nanodiamonds through the stabilization heat treatment of diamonds using Ga-based, Sn-based, or In-based liquid metals. In the case of nanodiamonds, nanodiamonds and nanographite are mixed, so the nanographite must be removed. By using Ga-based, Sn-based, or In-based liquid metals, only nanodiamonds can be selectively separated, and this method has the advantage of being able to process the material in a much shorter time compared to the removal of graphite using conventional strong oxidizing agents. Brief explanation of the drawing

[0021] Figure 1 is a photograph showing a balance capable of measuring to four decimal places for elemental weighing. Figure 2 is a photograph showing a prepared graphite crucible used to mix and charge various samples. Figure 3 is a photograph of a vacuum furnace. Figure 4 is a photograph showing samples (1. GFNS-dia, 2. GS-NdNc, 3. GS-dia) during hydrochloric acid etching. Figure 5 shows optical images of samples (1. GFNS-dia, 2. GS-NdNc, 3. GS-dia) that were filtered and dried after nitric acid etching. Figure 6 is an enlarged photograph of untreated mesh 20 diamond powder. Figure 7 is an enlarged photograph of diamond powder treated on GNFS alloy. Figure 8 is an enlarged photograph of diamond powder treated on GS alloy. Figure 9 is an enlarged photograph of NDNC powder treated on GS alloy. Figure 10 shows the Raman peaks of NDNC diamond before liquid metal treatment. Figure 11 shows the Raman peak after liquid metal treatment. In FIGS. 1 to 11 above, GFNS represents an alloy composed of a combination of gallium (Ga), nickel (Ni), iron (Fe), and silicon (Si), and GS represents an alloy composed of a combination of gallium (Ga) and silicon (Si). NDNC represents a form in which nanodiamond and nanocarbon are combined. GFNS-dia represents diamond treated on the GFNS alloy, GS NdNc represents NDNC treated on the GS alloy, and GS-dia represents diamond treated on the GS alloy. Specific details for implementing the invention

[0022] The present invention will be described in detail below.

[0023] In this specification, the terms "Ga-based alloy" or "gallium-based alloy" refer to an alloy having gallium as a basic element.

[0024] In this specification, the terms "Sn-based alloy" or "tin-based alloy" refer to an alloy having tin as a basic element.

[0025] In this specification, the terms "In-based alloy" or "indium-based alloy" refer to an alloy having indium as a base element.

[0026] In this specification, the term “diamond stabilization” means maintaining the intrinsic state of the diamond by suppressing or preventing the formation of graphite (which may be expressed as a graphite portion, graphite layer, graphite phase, graphitization, etc.) that may occur on the surface of the diamond.

[0027] In this specification, the term “nanodiamond” refers to diamond particles of very small size in the nanometer (1 to 100 nm) range. They are primarily manufactured through explosive synthesis, chemical vapor deposition (CVD), or mechanical grinding methods.

[0028] In one aspect, the present invention relates to a diamond stabilization method comprising the steps of: mixing diamond with one or more selected from the group consisting of gallium (Ga)-based alloys, tin (Sn)-based alloys, and indium (In)-based alloys, and heat-treating the mixture to produce a liquid metal; and separating the diamond from the liquid metal.

[0029] In another aspect, the present invention relates to a method for purifying nanodiamonds, comprising the steps of: mixing nanodiamonds with one or more selected from the group consisting of gallium (Ga)-based alloys, tin (Sn)-based alloys, and indium (In)-based alloys, and heat-treating the mixture to produce a liquid metal; and separating nanodiamonds from the liquid metal.

[0030] In another aspect, the present invention relates to a composition for purifying diamond or nanodiamond comprising one or more selected from the group consisting of gallium (Ga)-based alloys, tin (Sn)-based alloys, and indium (In)-based alloys.

[0031] In an exemplary embodiment, the gallium (Ga)-based alloy may comprise one or more elements selected from gallium (Ga) and tin (Sn), indium (In), bismuth (Bi), nickel (Ni), iron (Fe), silicon (Si), cobalt (Co) and germanium (Ge).

[0032] In an exemplary embodiment, the tin (Sn)-based alloy may comprise one or more elements selected from tin (Sn, Tin); and gallium (Ga, Gallium), indium (In, Indium), bismuth (Bi, Bismuth), nickel (Ni, Nickel), iron (Fe, Iron), silicon (Si, Silicon), cobalt (Co, Cobalt), and germanium (Ge, Germanium).

[0033] In an exemplary embodiment, the indium (In)-based alloy may comprise indium (In) and one or more elements selected from gallium (Ga), tin (Sn), bismuth (Bi), nickel (Ni), iron (Fe), silicon (Si), cobalt (Co) and germanium (Ge).

[0034] In an exemplary embodiment, the gallium (Ga)-based alloy may include gallium (Ga) and silicon (Si) or may include gallium (Ga), nickel (Ni), iron (Fe), and silicon (Si), and gallium (Ga) may be used as a diamond-phase stabilizer, nickel (Ni) as a carbon incorporation material, iron (Fe) as a carbon dispersant material, and silicon (Si) as a diamond-phase forming agent.

[0035] In an exemplary embodiment, the gallium (Ga)-based alloy may contain gallium in an amount of 65 to 95 weight%, preferably 70 to 90 weight%, more preferably 80 to 85 weight% with respect to the total alloy, but is not limited thereto.

[0036] In an exemplary embodiment, the gallium (Ga)-based alloy comprises gallium (Ga), nickel (Ni), iron (Fe), and silicon (Si), and may be included in amounts of 81.06 wt%, 9.65 wt%, 9.19 wt%, and 0.1 wt%, respectively, based on 100 wt% of the total alloy, but is not limited thereto.

[0037] In an exemplary embodiment, the heat treatment can be performed in a vacuum or at a pressure of 3 atmospheres or less, for example, at 0.01 atmospheres to 1 atmosphere.

[0038] In an exemplary embodiment, the heat treatment may be performed at a temperature of 800°C or higher, such as 1000°C or higher, 1100°C or higher, or 1200°C or higher.

[0039] In an exemplary implementation example, the heat treatment can be carried out using electric resistance heat, rapid light treatment, induction heating, plasma heat, laser heat, etc., and can also be carried out using various other methods such as microwave heating, infrared heat treatment, and high-frequency heating.

[0040] In an exemplary embodiment, diamond or nanodiamond in a liquid metal can be separated using a strong acid (e.g., hydrochloric acid, nitric acid, etc.).

[0042] The structure and effects of the present invention will be explained in more detail below with reference to examples. However, the following examples are provided for illustrative purposes only to aid in understanding the present invention, and the scope and range of the present invention are not limited by them.

[0044] [Example]

[0045] Stabilization of diamond during high-temperature atmospheric pressure treatment in a vacuum

[0046] (1-1) Sample preparation

[0047] Gallium, nickel, iron, and silicon elements were prepared and weighed using a balance capable of measuring to four decimal places so that the total weight was 10 g (Fig. 1). Specifically, the atomic percentages of Ga, Ni, Fe, and Si were set to 77.75 at%, 11 at%, 11 at%, and 0.25 at%, respectively, and the weight percentages were set to 8.106 wt%, 0.965 wt%, 0.919 wt%, and 0.01 wt%, respectively. All elements except gallium were prepared in the form of powder with a mesh size of 300 or less.

[0048] Micro-sized diamonds (grit, Iljin Diamond) ranging from 0.029g to 0.261g and 50% purified nanodiamonds were prepared.

[0049] Ga, Ni, Fe, and Si, which were weighed and prepared in advance, were placed in a graphite crucible, and diamond or refined nanodiamond was added as needed (Fig. 2). In addition, a sample was prepared by placing Ga, Ni, Fe, and Si in a quartz tube, adding diamond or nanodiamond as needed, and then vacuum-sealing it.

[0051] (1-2) Evaluation of Diamond Stabilization

[0052] The prepared graphite crucible was loaded using an ACE-VAC vacuum furnace, and heat treatment was performed (Fig. 3). Using a rotary pump and a diffusion pump, 10 -5After creating a vacuum up to torr, the heat treatment conditions were increased by 10°C per minute to set the target temperature to 1200°C and maintained for 2 hours. Subsequently, the power was turned off to allow for natural cooling. During this process, it was confirmed that as the vacuum level decreased above 1000°C, the vapor pressure of gallium dropped, causing it to deposit inside the chamber. However, since the crucible was covered with a lid, significant evaporation and deposition did not occur. In one batch, diamond and nanodiamond powders were mixed into a Ga-Si alloy and heat-treated to determine whether they had stabilized or decomposed.

[0053] After heat treatment, the Ga-based metal was dissolved in HCl, and the diamond powder was collected and examined using a filter to see what phase was formed. Accurate weighing was performed to determine whether the diamond had been converted into graphite or if the diamond phase had grown larger from the carbon crucible.

[0054] As a result, after treatment at 1200°C for 2 hours, all diamonds deposited in the GaNiFeSi alloy maintained the same weight, and no graphite phase was found on the surface in magnified analysis. This means that the diamond phase is stable in the proposed alloy system and that, unlike previous reports, diamond can be stabilized even at high temperatures above 1000°C.

[0056] (1-3) Separation and Analysis of Diamond in Ga-Si Alloy Using Hydrochloric Acid and Nitric Acid

[0057] Subsequently, the prepared samples were each dissolved in 35% hydrochloric acid (HCl) at 120°C for 4 hours (Fig. 4). Since hydrogen gas reacts to form a passivation film during this process, the samples were washed and then treated in a 65% nitric acid solution at 120°C for 4 hours to complete the process. Although NOx gas was generated during this process, it was safely vented during treatment. Afterward, etching of all gallium-based samples was performed using nitric acid. Subsequently, the reacted liquid nitric acid and the remaining diamond were separated using a filter and dried to identify the remaining diamond and residue (Fig. 5).

[0059] (1-4) Results of expanded analysis

[0060] The appearance of untreated diamond powder with a diameter of 1000 µm is shown in Fig. 6. Manufactured by Iljin Diamond, it is characterized by having a yellow color due to the presence of nitrogen and the N3 center.

[0061] Figure 7 shows a sample containing GNFS-dia, confirming that the body color changed after treatment. Generally, it is reported that a graphite layer forms on the surface of diamond at high temperatures of 1200°C; however, in this experiment, the introduced diamonds were clustered at the bottom of the alloy, and no graphitization occurred. Instead, the body color of the diamonds changed to gray, indicating that the type of nitrogen centers changed due to the heat treatment. In other words, the GNFS alloy had the characteristic that the diamonds did not float due to density differences but were fixed at their original loading location at the bottom by the viscosity of the solution. This effectively prevented surface graphitization while producing the secondary effect of a color change.

[0062] Figure 8 shows a sample containing GS-dia, and it can be confirmed that the body color also changed. At a high temperature of 1200°C, no graphite layer was formed on the surface, and the color changed to a lighter gray than that of the sample containing GNFS-dia. Similarly, the diamonds loaded at the bottom did not float to the surface due to the GS alloy and remained at the bottom even after solidification. After solidification, separation occurred without contact with the diamond surface, resulting in a large amount of powder. In other words, this means that the problem of the diamonds at the bottom floating to the top did not occur because the GS alloy had high viscosity even in the molten state.

[0063] Figure 9 shows the appearance of the residue remaining on the filter paper after nitric acid etching treatment of an alloy containing GS-ndnc 50% nanodiamond powder. Although the appearance is similar to that of the nanodiamond powder initially added, it was not possible to confirm with an optical microscope whether more nanodiamond phases were formed. However, it was confirmed that at least not all of the material was transformed into nanographite, based on the fact that a large amount of residue remained even after the filter paper treatment. This implies that a diamond phase with excellent corrosion resistance remains.

[0065] Selective graphite removal of nanodiamonds

[0066] After weighing nanodiamond (ND) and nanographite (NG) powders and performing Raman analysis, the ND, NG, and Ga-based alloys were placed in a quartz tube and vacuum-sealed. Subsequently, heat treatment was carried out by maintaining the temperature at 1000°C for 2 hours. After heat treatment, the Ga-based alloy was dissolved in HCl to collect the diamond powder; subsequent verification, weighing, and Raman analysis confirmed that the ND powder could be selectively isolated and that the NG powder had been converted to ND. Raman analysis revealed an inversion of the diamond and G peaks. Specifically, when examining the Raman peaks of NDNC diamond before liquid metal treatment, the graphite peaks occupied the majority in the 1600–2500 region (Fig. 10); however, after liquid metal treatment, characteristic peaks appeared in the 1300 (diamond) and 1600 regions (Fig. 11).

Claims

Claim 1 A diamond stabilization method comprising the steps of: mixing diamond with one or more selected from the group consisting of gallium (Ga)-based alloys, tin (Sn)-based alloys and indium (In)-based alloys, and heat-treating the mixture to produce a liquid metal; and separating the diamond from the liquid metal. Claim 2 A method for purifying nanodiamonds comprising the steps of: mixing nanodiamonds with one or more selected from the group consisting of gallium (Ga)-based alloys, tin (Sn)-based alloys and indium (In)-based alloys, and heat treating the mixture to produce a liquid metal; and separating nanodiamonds from the liquid metal. Claim 3 A method according to claim 1 or 2, wherein the gallium (Ga)-based alloy comprises one or more elements selected from gallium (Ga); and tin (Sn), indium (In), bismuth (Bi), nickel (Ni), iron (Fe), silicon (Si), cobalt (Co), and germanium (Ge). Claim 4 A method according to claim 1 or 2, wherein the tin (Sn)-based alloy comprises one or more elements selected from tin (Sn, Tin); and gallium (Ga, Gallium), indium (In, Indium), bismuth (Bi, Bismuth), nickel (Ni, Nickel), iron (Fe, Iron), silicon (Si, Silicon), cobalt (Co, Cobalt), and germanium (Ge, Germanium). Claim 5 A method according to claim 1 or 2, wherein the indium (In)-based alloy comprises indium (In); and one or more elements selected from gallium (Ga), tin (Sn), bismuth (Bi), nickel (Ni), iron (Fe), silicon (Si), cobalt (Co) and germanium (Ge). Claim 6 In paragraph 3, the gallium (Ga)-based alloy comprises gallium (Ga), nickel (Ni), iron (Fe), and silicon (Si). Claim 7 A method according to claim 1 or 2, wherein the heat treatment is performed at a pressure of 3 atmospheres or less or in a vacuum state. Claim 8 A method according to claim 1 or 2, wherein the heat treatment is performed at a temperature of 800°C or higher. Claim 9 In claim 1 or 2, the method is a method of separating diamonds in the liquid metal with a strong acid. Claim 10 A composition for refining diamonds comprising one or more selected from the group consisting of gallium (Ga)-based alloys, tin (Sn)-based alloys, and indium (In)-based alloys. Claim 11 A composition in which, in item 10, the diamond is a nanodiamond.

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