WO2023035287A1

WO2023035287A1 - Diamond film coated ornament and preparation method for diamond film coating

Info

Publication number: WO2023035287A1
Application number: PCT/CN2021/118355
Authority: WO
Inventors: 吕反修
Original assignee: 吕反修; 何金鑫
Priority date: 2021-09-13
Filing date: 2021-09-14
Publication date: 2023-03-16
Also published as: CN114293169A; WO2023035429A1

Abstract

The present disclosure relates to a diamond film coated ornament and a preparation method for a diamond film coating, and belongs to the field of chemical coatings. The diamond film coated ornament, characterized in that a surface of a moissanite ornament is plated with a diamond film coating, and the diamond film has an average crystal grain size of 50 nm-200 nm, a surface roughness of less than 10 nm, and a thickness of 0.1-0.5 μm. The method may achieve a uniform and dense diamond film coating with a good optical performance on the surface of the moissanite ornament. The moissanite ornament plated with a diamond film on the surface thereof prepared by the method may show various physicochemical properties of diamond while maintaining the optical performance (fire) of moissanite, and the surface hardness thereof reaches the hardness of diamond, which greatly improves the scratch resistance of moissanite.

Description

A kind of diamond film coating ornament and the method for preparing diamond film coating

technical field

The invention relates to a diamond film coating ornament and a method for preparing the diamond film coating, belonging to the field of chemical coating.

Background technique

Moissanite is a single crystal form of silicon carbide (SiC), which does not exist naturally in the Earth's environment (Moissanite is found in craters and is believed to come from extraterrestrial bodies). Synthetic moissanite is an excellent wide-bandgap semiconductor material, and it is one of the main research objects of a new generation of high-performance semiconductor materials around the world. The refractive index of moissanite is 2.46-2.59, which is higher than that of diamond (diamond) (2.42), so its brilliance (fire color) is better than that of diamond. In addition, its thermal conductivity is also very high (490W/cm.K), so it is a high imitation diamond with the highest fidelity with diamond (diamond). Although Moissanite is also very hard (Mohs hardness 9.2), it is still significantly different from diamond hardness (Mohs hardness 10). Therefore, a layer of diamond film (diamond) film is applied on the surface of Moissanite jewelry, so that it has the same physical and chemical properties as diamonds, but also has the same high hardness as diamonds, and it will never wear and tear like diamonds. "Grains will last forever" has become the goal pursued by people.

Before the present invention, Neogi et al disclosed in US Patent (US20160029748A1) a method for preparing a nano-diamond coating on the surface of various gem ornaments including Moissanite by using a nano-diamond powder slurry dip coating method. However, the slurry dipping method is essentially a physical method. The adhesion between the nano-diamond coating and the gemstone substrate only comes from the "Van der Waals force" between the nano-diamond particles and the gemstone surface atoms, which is a weak force. force, thus resulting in poor adhesion. In addition, it is difficult to ensure the uniformity and repeatability of the coating thickness by the slurry dipping method. More importantly, the optical performance of nano-diamond powder is poor, which affects the fire color of gemstones after coating. This is completely unacceptable for gem jewelry.

K. Nassau et al once disclosed in the patent (CN108823550A, WO98/21386) a method of applying a diamond film coating on the surface of moissanite (Moissanite) ornaments by chemical vapor deposition (CVD). Due to the special shape of gem ornaments (such as diamond rings), K. Nassau and others designed a sample table with a round hole, so that the diameter of the round hole is slightly smaller than the girdle diameter of the diamond ring ornaments. In this way, the pavilion of the pointed (inverted cone) can be placed firmly in the round hole, and the table and crown of the diamond ring are placed in the diamond film deposition atmosphere (H ₂ /CH ₄ , or H ₂ / CH ₄ /Ar high temperature or high temperature plasma atmosphere) to achieve the purpose of depositing diamond film.

However, since the pavilion of the diamond ring jewelry is in the shape of an inverted pyramid, there are only a few edges of the pavilion in contact with the circular hole, and they are all point contacts, which will inevitably lead to a high temperature (or high temperature plasma) atmosphere for diamond film deposition. The heat conduction between the moissanite sample in the sample and the sample stage becomes extremely poor (thermal blockage). As a result, the Moissanite sample will inevitably heat up rapidly until it is higher than the optimum temperature range (700-1000°C) required for diamond film deposition. In order to reduce the surface temperature of the Moissanite sample, it is necessary to reduce the input power or reduce the gas pressure in the deposition chamber. If the temperature requirement for the deposition of the diamond film cannot be met, the Moissanite sample can only be moved from the high-temperature gas flow (or high-temperature plasma). Open, but had to use the so-called remote deposition (Remote Deposition) mode. This is just the reason why K. Nassau et al. used microwave plasma remote deposition and very low pressure (2Torr, normal diamond film deposition pressure is 20-400Torr) in the two embodiments of the patent application (see CN108823550A; WO98/21386 page 13).

However, for moissanite jewelry (as for any gemstone jewelry), maintaining the color (fire color) after coating is the most critical technical requirement. This means that the diamond film must have the highest possible optical performance and the lowest possible surface roughness (since the surface roughness of the diamond film is directly related to the thickness of the diamond film, this requires that the thickness of the diamond film should not be too large). It is well known that atomic hydrogen concentration is the decisive factor for the optical quality of diamond films, and the preparation of high optical quality diamond films (especially high-quality diamond single crystals) requires very high atomic hydrogen concentration. Such conditions can only be realized under the condition of high power, high pressure, and the distance from the excitation source (high-temperature hot wire, microwave plasma ball, or DC arc plasma torch nozzle, etc.) as small as possible (see: "diamond film Preparation and Application", the first chapter, edited by Lu Fanxiu, Volume 1, Science Press, 2014). Obviously, the use of microwave plasma remote deposition by K. Nassau et al. runs counter to this in the embodiment, and it is really a last resort.

In the early research work, the present inventor used a circular hole sample stage similar to K. Nassau, and used DC arc plasma jet CVD and microwave plasma CVD systems to carry out high-quality (D color) carat grade moissanite. Trials of deposited diamond film coatings on jewelry tabletops and crowns. It is found that when DC arc plasma spraying is used, the diamond film can only be deposited barely under the conditions far away from the optimum deposition process, and the quality of the film is extremely poor. As shown in Figure 1.

The present invention aims at the defect that the above-mentioned circular hole sample stage cannot effectively dissipate heat, and proposes an improved sample stage design, which changes the thermal contact between the moissanite and the sample stage from point contact to surface contact, so that it can High optical quality diamond film-coated moissanite ornaments were prepared under conditions within a range of quality diamond film deposition process parameters. In addition, the present invention also proposes a surface pretreatment method that can greatly increase the nucleation rate of the diamond film on the moissanite surface, aiming at the requirement of extremely low surface roughness of the optical coating. At the same time, the preparation process of diamond film-coated moissanite jewelry was optimized.

Contents of the invention

The object of the present invention is to provide a diamond film coated ornament.

Another object of the present invention is to provide a method for preparing a diamond film coating on the surface of an ornament.

A diamond film-coated ornament is characterized in that a layer of diamond film coating is coated on the surface of the moissanite ornament, the average grain size of the diamond film is 50 nanometers to 200 nanometers, the surface roughness is less than 10nm, and the thickness of the diamond film is 0.1-200 nanometers. 0.5 microns.

The diamond film-coated ornament is prepared through the following steps:

1) Ultrasonic grinding pretreatment is carried out to moissanite jewelry in the suspension of nano-diamond powder; The time is 1 hour ∽ 6 hours;

2) Moissanite ornaments are taken out from the nano-diamond powder suspension, and cleaned;

3) Apply a certain force to the moissanite jewelry, and press it into the pre-set inverted conical hole of the pure copper conformal sample stand, so that it forms a close contact with the conical hole, that is, surface contact, and the pressure is 50kgf∽ 250kgf;

4) Place the moissanite jewelry together with the conformal sample stage in a diamond film deposition furnace for plasma treatment, the temperature of the plasma treatment is 700°C∽1000°C, and the time of the plasma treatment is 5 minute ∽ 30 minutes;

5) Introduce methane for in-situ diamond film deposition; diamond film deposition adopts "two-stage method": nucleation stage and growth stage, the concentration of methane in the nucleation stage is 3%∽10%, and the time is 5∽20 minutes; The methane concentration in the growth stage is 0.5%∽2%, and the time is 10 minutes∽120 minutes; the pressure of the deposition furnace is set at 3kPa∽20kPa.

In the step 4) and step 5), the plasma treatment and the in-situ diamond film deposition adopt DC arc plasma jet CVD or microwave plasma CVD.

The moissanite jewelry adopts nano-diamond suspension for ultrasonic grinding pretreatment; the diamond particle size in the nano-diamond suspension is between 5 nanometers and 200 nanometers, and the concentration of the nano-diamond particles is 5%-20%. Grinding pretreatment time is 1 hour∽6 hours.

The pure copper conformal sample stage has an inverted conical conformal hole, and its cone angle is slightly smaller than that of the inverted pyramid at the moissanite jewelry pavilion, with a deviation of 0°∽-2°, and a certain force will be applied during use. The moissanite jewelry is pressed into the inverted conical conformal hole of the conformal sample stand, forcing the conical hole to undergo plastic deformation, forming surface contact with the edges and corners of the moissanite jewelry pavilion placed on it.

The diamond film-coated ornament described in this application is prepared through the following steps:

An improved conformal hole sample stage. It can be used to prepare diamond film-coated moissanite ornaments with high optical quality.

The round hole sample stage proposed by K. Nasuo et al. in the patent (CN108823550A, WO98/21386) cannot effectively dissipate heat, and cannot prepare high optical quality diamond films on the surface of moissanite jewelry within the normal deposition process parameter range of high quality diamond films Coating defects, a sample stage design with a conical hole similar in shape (conformal) to the inverted pyramid shape of the diamond ring jewelry pavilion was proposed. The cone angle of the conical hole is slightly smaller than the cone angle (96°C) of the pavilion of the diamond ring. Then apply a certain pressure to press the diamond ring jewelry pavilion into the conformal hole of the sample stage, forcing the conical hole and the edge contact part of the diamond ring jewelry pavilion pyramid to undergo plastic deformation, thereby forcing its contact properties from point contact (sample stage protection) The cone angle of the shape hole is slightly smaller than the cone angle of the diamond ring jewelry pavilion, and it is impossible to form a perfect line contact) to surface contact. The conformal sample stage should be made of materials with high thermal conductivity, easy deformation, and resistance to high temperature and atomic hydrogen etching in the diamond film deposition environment. Pure copper is the best choice. Although molybdenum and tungsten have good thermal conductivity, they are difficult to undergo plastic deformation. Graphite has good thermal conductivity and plastic deformation ability, but it is very easy to be etched by atomic hydrogen, so it is not recommended to use . The conformal inverted cone sample stage made of pure copper can greatly improve the heat conduction ability from the diamond ring sample through the sample stage during the diamond film deposition process, so that it can be processed under conditions close to high optical quality diamond film deposition (high power, high pressure , close distance (from the excitation source)) to deposit high optical quality diamond film coating on the surface of the diamond ring jewelry (table and crown). This is further illustrated in Figure 2.

A method for realizing uniform nucleation of ultra-high-density diamond (greater than 10 ¹⁰ /cm ² ) on the surface of moissanite jewelry.

The present invention adopts a method for ultrasonically grinding and pretreating moissanite ornaments in a suspension of nano-diamond powder to achieve the purpose of uniform nucleation of ultra-high-density diamonds. Although it has been reported in the literature that ultra-high-density diamond nucleation is achieved by ultrasonic grinding of nano-diamond suspensions, most of the substrate materials used are single crystal silicon or silicon oxide (OAWilliams et al.Diamond & Related Materials 15 (2006) 654 –658), the diamond nucleation density can reach 10 ¹⁰ -10 ¹² /cm ² . However, the present invention utilizes nano-diamond suspension to carry out ultrasonic pretreatment on moissanite ornaments to realize ultra-high density diamond nucleation, so far there is no literature report. And the diamond nucleation density is as high as 2.5x10 ¹³ /cm ² . It strongly guarantees the diamond film coating with extremely low surface roughness. The surface roughness of the diamond film coating finally obtained by the present invention is less than Ra 10nm. An example of ultra-high-density uniform nucleation of a diamond film is shown in Figure 3.

A method for coating a diamond film on the surface of a moissanite ornament, the method comprising the following steps: step 1: carrying out ultrasonic grinding pretreatment to the moissanite ornament in a suspension of nano-diamond powder; step 2: removing the moissanite ornament from The nano-diamond powder suspension is taken out, followed by ultrasonic cleaning with deionized water and absolute ethanol (alcohol); step 3: pressing the moissanite jewelry into the inverted tapered hole of the pre-selected conformal sample stage ; Step 4: placing the moissanite jewelry together with the conformal sample stage in a diamond film deposition furnace for plasma treatment; Step 5: injecting methane for in-situ diamond film deposition.

Further, in step 1, the nano-diamond particle size in the nano-diamond powder suspension is between 5 nm and 200 nm, and the concentration of the nano-diamond powder is 5%∽20%.

Furthermore, the time for the ultrasonic grinding pretreatment in the nano-diamond suspension is 1 hour∽6 hours.

Further, in step 3, the material of the conformal sample stage is pure copper.

Further, the conformal sample stage is provided with an inverted conical hole for placing moissanite ornaments, and its cone angle is slightly smaller than the cone angle of the moissanite ornament pavilion (deviation is 0° to -2°). In step 3, a pressure of 50Kgf∽250Kgf (depending on the size of the moissanite ornament) is used to press the moissanite ornament into the inverted tapered hole of the conformal sample holder.

Further, in step 4, the plasma treatment adopts DC arc plasma injection or microwave plasma.

Further, the temperature of the plasma treatment is 700°C-1000°C, and the time of the plasma treatment is 5 minutes-30 minutes. The purpose of plasma treatment is to completely remove the remaining organic root groups (derived from nano-diamond suspension) on the surface of moissanite jewelry, and activate the surface of moissanite jewelry.

Further, the in-situ deposition of the diamond film in step 5 includes the following two stages: nucleation and growth of the diamond film. The concentration of methane in the nucleation stage is 3%-10%, and the time is 5-20 minutes; the methane concentration in the growth stage is 0.5%-2%, and the time is 10 minutes-120 minutes. The pressure of the deposition furnace is set at 3kPa-20kPa.

Through the method of the invention, a uniform and dense diamond film coating with excellent optical properties can be obtained on the surface of the moissanite jewelry. The moissanite ornaments coated with diamond film on the surface prepared by the method of the present invention can show various physical and chemical properties of diamond while maintaining the optical properties (fire color) of moissanite, and its surface hardness reaches the hardness of diamond. It can greatly improve the scratch resistance of moissanite.

An improved method for preparing high optical quality diamond film coating on the surface of moissanite jewelry. The prepared diamond film coated moissanite jewelry has the hardness and excellent hardness of diamond while maintaining the fire color of moissanite. scratch resistance performance. A pure copper conformal sample stage with an inverted conical hole that can be used for the preparation of diamond film-coated moissanite jewelry. The moissanite jewelry pavilion forms a surface contact, making it possible to deposit a high optical quality diamond film on the surface of the moissanite jewelry. A method for realizing ultra-high density diamond nucleation on the surface of moissanite jewelry. Ultrasonic grinding in nano-diamond suspension, combined with an optimized nucleation process, enables the diamond nucleation density to reach 2.5x10 ¹³ /cm ² . A method for preparing a high-optical-quality diamond film on the surface of a moissanite ornament, the method comprising the following steps: Step 1: Ultrasonic grinding pretreatment of the Moissanite ornament in a nano-diamond suspension; Step 2: Moissanite The ornaments are taken out from the nano-diamond powder suspension and cleaned; step 3: pressing the moissanite ornaments into the pre-set conformal sample stage so that it forms surface contact with the inverted tapered hole of the sample stage; step 4 : Place the moissanite jewelry together with the conformal sample stage in a diamond film deposition furnace for plasma treatment; step 5: feed methane, and use a two-stage method (nucleation stage and growth stage) to carry out the in-situ diamond film deposition. The moissanite ornament coated with a diamond film on the surface of the present invention can maintain the optical performance (fire color) of the moissanite ornament while having various physical and chemical properties of diamond, and the surface hardness has reached the hardness of diamond, and has excellent Anti-scratch properties. By adopting the technology of the invention, batch deposition of diamond film-coated moissanite ornaments can be realized.

The prepared diamond film-coated moissanite jewelry has the same fire color as the uncoated moissanite jewelry, and also has the hardness of diamond and excellent scratch resistance. It is a high-performance high imitation diamond product .

The preparation method described in the application can effectively overcome the poor thermal contact of the special-shaped moissanite (such as diamond ring) jewelry with the sample stage during the diamond film deposition process, it is difficult to obtain high quality, high light transmittance diamond film coating, and a large number of The temperature and the uniformity of the chemical vapor environment during the simultaneous deposition of samples are difficult. With the help of the technology disclosed in the invention, the industrialized production of diamond film-coated Moissanite can be realized.

Description of drawings

Figure 1 uses DC arc plasma jet diamond film CVD equipment, and the diamond-coated Moissanite jewelry prepared with a round-hole copper sample stage (see Figure 2 on the right) cannot obtain high optical quality diamond film coatings. Left: 6.5mm (1 carat) D color Moissanite uncoated sample (rough stone); Middle: The distance between the sample stage and the nozzle of the plasma torch is 60mm, the pressure is 2.3KPa (17Torr), the methane concentration is 1%, the input power 8KW. The surface temperature of the Moissanite sample was as high as 1150°C, and the surface of the sample was completely blackened after only 10 minutes of deposition; Right: High-quality optical-grade F60mm self-supporting diamond film (unpolished) grown on the same equipment. Process conditions: nozzle distance 20mm, input power 20KW, pressure 6KPa (45Torr), methane concentration 0.5%, temperature 900°C, time 24 hours;

Figure 2 Conformal pure copper sample stage with inverted conical hole. Left: Hole design for an inverted conical hole. The taper angle is 96°, the tolerance is 0o∽-2o, the diameter of the taper hole is slightly smaller than the girdle diameter of the diamond ring to be coated, and a small-diameter round hole is designed in the lower part to prevent the tip of the diamond ring pavilion from breaking when it is pressed in. Before the diamond film is deposited, the moissanite jewelry to be coated is pressed into the conformal hole, forcing the plastic deformation of the contact part between the conformal hole and the inverted cone-shaped pavilion of the moissanite jewelry, thereby forming a surface contact. Right: Schematic diagram of the hole shape of the round hole sample stage used by K. Nasso et al. The diameter of the hole is slightly smaller than the girdle diameter of the moissanite jewelry. Put the moissanite jewelry in the round hole before deposition, and the edge of the inverted pyramid pavilion of the moissanite jewelry is in point contact with the round hole;

Fig. 3 Field emission scanning electron micrograph of ultra-high density diamond nucleation. Nucleation pretreatment: Sonication in 30nm nanodiamond suspension for 2 hours. Nucleation process: DC arc plasma CVD system is adopted, the nozzle distance is 25mm, the pressure is 6KPa, the power is 10KW, the methane concentration is 4%, and the nucleation time is 10 minutes. The size of the diamond crystal nucleus shown in the figure is only 15-20nm, and the diamond nucleation density is as high as 2.5x10 ¹³ /cm ² ;

Figure 4 Comparison of fire color between diamond film coated Moissanite and uncoated (raw stone). Left: Uncoated, Right: Coated. A DC arc plasma jet CVD system is used. Coating process: nucleation: nozzle distance 25mm, pressure 6KPa, power 10KW, methane concentration 4%, nucleation time 10 minutes; growth: methane concentration reduced to 1%, time: 30 minutes;

Figure 5: Field emission scanning electron microscope (FSEM) image of the diamond film-coated Moissanite surface topography shown in Figure 4. It can be seen that the continuous dense diamond film shows obvious diamond (111) micro-facet characteristics, the average grain size is about 80-100nm, and the surface roughness is less than 10nm;

Figure 6 The small-angle X-ray diffraction spectrum of the diamond film-coated Moissanite surface, clearly sharp (111) and (220) diamond diffraction peaks can be seen. Illustrate that shown in Fig. 5 is indeed polycrystalline diamond film;

Figure 7 left: the surface morphology of diamond film-coated moissanite prepared by ultrasonic grinding of 5 micron and 1 micron mixed diamond powder for 2 hours pretreatment nucleation method and two-stage method (nucleation and growth). Discrete large-sized grains appear, and the fire color of the coated Moissanite becomes poor; Right: The surface morphology of the diamond film-coated Moissanite grown directly after cleaning without any pretreatment. The uniformity of the diamond film is very poor, the grain size is very large, and it is not dense, and the Moissanite sample is completely devitrified after deposition (see accompanying drawing 1). Illuminated the present invention adopts the superiority of nano-diamond suspension;

Fig. 8 Vickers hardness indentation photos of diamond film-coated Moissanite. The HVT-100 microhardness tester produced by Shanghai Lianer Testing Equipment Co., Ltd. was used for testing. Standard diamond pyramid indenter is used. The load P is 0.025kg (0.245N), and the holding time is 10 seconds. Test 10 points for each sample, measure the diagonal length of the diamond film-coated Moissanite hardness indentation with a laser confocal microscope, and calculate the Vickers hardness according to the formula: Hv=1854.4P/a ² . The microscale in the figure is 4 mm. The Vickers hardness calculated according to the indentation measurement data shown in the figure is as high as 117GPa, the average hardness calculated according to 10 test points is 84±7GPa, and the diamond hardness is 80-110GPa. The diamond film coating moissanite prepared by the technology of the present invention has reached the hardness of diamond;

Figure 9. Scratch resistance of diamond film-coated Moissanite. The scratch tester is used for testing, single crystal diamond stylus, the maximum scribing pressure is 20N, the scribing distance is 2mm, and the acoustic emission signal is recorded while scratching. (a) Uncoated sample (rough stone): The acoustic emission signal begins to appear at about 8N (the signal at 3N is the noise when the screw accidentally lands). The optical microscope image shows that the scribe needle has been carved into the moissanite, forming obvious grooves, showing many discontinuous lateral cracks on both sides of the grooves, corresponding to a series of discontinuous acoustic emission peaks on the acoustic emission spectrum. (b) Moissanite coated with diamond film; the acoustic emission peak does not appear until it is close to 20N. According to the light microscope photo, the scribing needle has broken the surface of the diamond film at this time, and the diamond film has a brittle fracture, and the fracture is very smooth. It has been rolled up, indicating that the diamond film itself has not a small stress, and it is compressive stress.

Figure 10. Thickness of diamond film coating. The thickness of the diamond film coating was measured under a field emission scanning electron microscope using a prefabricated fractured mosaic sample. The thickness of the diamond film coating measured from the fracture image shown in the figure is 0.2-0.3 μm;

Fig. 11 adopts the 6.5mm (1 carat) diamond film-coated Moissanite drill produced in batches by the technology of the present invention. The diameter of the sample stage is 62mm, which can allow 55 grains of 6.5mm (1 carat) diamond film-coated Moissanite to be deposited at one time;

Figure 12 is a comparison of fire color of diamond film-coated Moissanite and uncoated sample (raw stone) prepared by microwave plasma CVD system. Center position: Uncoated rough, left and right diamond coated samples. Adopt 6KW domestic microwave plasma CVD system. Power: 3KW; Pressure: 4.04KPa; Methane concentration: 5%; Plasma etching time: 5 minutes; Deposition time: 1.5 hours; The pretreatment process is the same as DC arc plasma CVD.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings.

The most important core content of the present invention is the fundamental improvement of the circular hole sample stage that K. Nassau et al adopt in its disclosed patent technology.

Referring to accompanying drawing 1, adopt the same round-hole pure copper sample stage as K. Nassau et al., and deposit diamond film on moissanite jewelry with DC arc plasma jet CVD system. Accompanying drawing 1 left side: be 6.5mm (1 carat) uncoated moissanite (original stone); Middle: diamond film coating moissanite, deposition condition is: the distance between sample platform and plasma torch spout is 60mm, and pressure is 2.3KPa (17Torr), the methane concentration is 1%, and the input power is 8KW. The surface temperature of the Moissanite sample was as high as 1150°C, and the surface of the sample was completely blackened after only 10 minutes of deposition; right: a high-quality optical-grade Φ60mm self-supporting diamond film (unpolished) grown on the same equipment. Process conditions: nozzle distance 20mm, input power 20KW, pressure 6KPa (45Torr), methane concentration 0.5%, temperature 900°C, time 24 hours. It can be seen from accompanying drawing 1 that the circular hole sample stage designed by K. Nassau et al. can only deposit diamond film under normal deposition conditions (low power, low pressure, long distance). Even so, the quality of the diamond film is too poor to meet the requirements for high optical quality diamond film coatings.

For this purpose with reference to accompanying drawing 2, the present invention has designed a kind of inverted conical hole conformal pure copper sample stage. Left: Schematic diagram of the hole shape design for an inverted conical hole. The taper angle is 96°, the tolerance is 0° to -2°, the diameter of the taper hole is slightly smaller than the girdle diameter of the diamond ring to be coated, and a small-diameter round hole is designed in the lower part to prevent the tip of the diamond ring from breaking when it is pressed in. Before the deposition of the diamond film, the moissanite jewelry to be coated is pressed into the conformal hole, forcing the plastic deformation of the contact part between the conformal hole and the inverted cone-shaped pavilion of the moissanite jewelry, thereby forming a surface contact. Right: Schematic diagram of the hole shape of the round hole sample stage used by K. Nasso et al. The diameter of the hole is slightly smaller than the girdle diameter of the moissanite jewelry. Put the moissanite jewelry on the round hole before deposition, and the edge of the inverted pyramid pavilion of the moissanite jewelry is in point contact with the round hole;

Another core content of the present invention is to realize ultra-high density (more than 10 ¹⁰ /cm ² ) diamond nucleation technology on the surface of Moissanite samples. The optical properties of diamond film coatings depend on the intrinsic optical quality of the coating (i.e., the absorption coefficient, related to crystal structure and crystal defects) and the surface roughness of the diamond film (directly related to surface scattering). For optical coatings with very small thicknesses, the influence of surface roughness on optical properties is more important than that of crystal intrinsic quality.

Referring to accompanying drawing 3, the present invention adopts a nucleation pretreatment method of ultrasonic grinding in nano-diamond suspension to greatly increase the diamond nucleation density. As shown in the field emission scanning electron microscope photo in Figure 3, the diamond nucleation density is as high as 2.5x10 ¹³ /cm ² , and the specific process conditions are: the particle size of nano-diamond is 30 nm, and the ultrasonic treatment time is 2 hours: DC arc plasma CVD system is used , nozzle distance 25mm, pressure 6KPa, power 10KW, methane concentration 4%, nucleation time 10 minutes. Obtaining such a high diamond nucleation density on moissanite jewelry has not been reported in any literature so far. The original magnification of accompanying drawing 3 is 50,000 times, and the scale in the figure is 2 microns.

Another core content of the present invention is to form an optimized method for applying high optical quality diamond film coating on Moissanite. Its specific content is as follows:

The method includes the following steps: Step 1: performing ultrasonic grinding pretreatment on moissanite jewelry in nanometer diamond powder suspension. Wherein, the particle size of the nano-diamond powder is between 5 nanometers and 200 nanometers, the concentration of the nano-diamond powder is 5%∽20%, and the pretreatment time of ultrasonic grinding is 2 hours∽6 hours. The purpose of this step is mainly to increase the nucleation density of the diamond film deposition, so that the nucleation density of the diamond film is greater than 10 ¹⁰ cm ^-2 .

After ultrasonic grinding pretreatment, in step 2: take out the moissanite jewelry from the nano-diamond powder suspension, and clean it, and use deionized water and absolute ethanol (alcohol) to ultrasonically clean it according to the cleaning procedure. blow dry.

After the moissanite jewelry has been pre-treated and cleaned by ultrasonic grinding, in step 3: the moissanite jewelry is pressed into a preset conformal sample stage for maintenance. Wherein, taking Moissanite as an example, in order to keep Moissanite, with reference to Figure 2, an inverted conical hole for maintaining a Moissanite jewelry can be provided in the conformal sample stand, and the depth of the conical hole is about 4/5 of the bottom depth, the cone angle of the inverted cone is roughly 96°, and the tolerance of 0°∽-2° is specially designed. In order to facilitate the pressing of Moissanite drills, the best choice for the material of the conformal sample stage is pure copper. Moissanite can be pressed into the inverted conical hole of the conformal sample stage by applying a pressure of 50Kgf∽250Kgf, forcing it to form surface contact with the inverted conical hole of the copper sample stage.

After ultrasonic grinding pretreatment, and Moissanite is pressed into the inverted conical hole of the conformal sample stage, in step 4, the Moissanite jewelry is placed together with the conformal sample stage in the diamond film deposition furnace for plasma treatment . In step 4, diamond film deposition methods such as DC Arc Plasma Jet (DC Arc Plasma Jet) CVD, microwave plasma CVD (MWCVD), and hot wire CVD (HFCVD) can be used for diamond film coating of Moissanite. However, due to the low degree of gas activation in hot-wire CVD, the concentration of atomic hydrogen is too low, and it is difficult to obtain diamond thin film coatings with good optical properties. Therefore, in step 4, plasma treatment employs DC arc plasma jet or microwave plasma. The temperature of the plasma treatment is 700°C∽1000°C, and the time of the plasma treatment is 5 minutes∽30 minutes. To completely remove the influence of any organic root group (derived from nano-diamond powder suspension) remaining on the surface of Moissanite on the deposition of diamond film, and activate the surface state of the Moissanite sample, which is conducive to the uniform deposition and improvement of diamond film Adhesion of diamond film.

After the plasma treatment is completed, in step 5: methane is introduced, and then the in-situ diamond film deposition is carried out. The in-situ deposition of the diamond film described in step 5 includes the following two stages: nucleation and growth of the diamond film. The concentration of methane in the nucleation stage is 3%∽10%, and the time is 5∽20 minutes; the concentration of methane in the growth stage is 0.5%∽2%, and the time is 10 minutes∽120 minutes. The pressure of the deposition furnace is set to 3kPa∽20kPa.

After the deposition is completed, cool for 10 minutes to take out the coated Moissanite sample.

Further with embodiment below, in conjunction with accompanying drawing, carry out more specific description:

Example 1: Batch deposition of diamond film-coated Moissanite jewelry by DC arc plasma jet CVD system

Hereinafter, an example of a diamond film coating on a Moissanite (1 carat) with a diameter of 6.5 mm will be further described.

Moissanite samples were first ultrasonically milled in a 30 nm diamond powder suspension for 2 h.

Take out the Moissanite sample and clean it.

Press it into a prefabricated inverted tapered hole on the surface of a copper conformal sample stage with a height of 30mm and a diameter of 62mm (cone angle 96°, tolerance 0°∽-2°) with a force of 150kg.

Put the Moissanite sample into a DC arc plasma CVD diamond film deposition furnace, and treat it in argon/hydrogen plasma for 5 minutes (Ar: 3slm; H2: 8slm; chamber pressure: 3∽20kPa; plasma torch current: 90 ∽120A; voltage: 97∽110V; nozzle distance: 25mm). Then adopt the two-stage method for in-situ diamond nucleation and growth: the concentration of methane in the nucleation stage is 3%∽10%, and the time is 5∽20 minutes; the concentration of methane in the growth stage is 0.5%∽2%, and the time is 10 minutes∽ 120 minutes. The sample surface temperature is 700∽1000°C.

After the deposition is completed, the current is cut off to terminate the deposition of the diamond film, and the coated Moissanite sample can be taken out after cooling for 10 minutes.

With reference to accompanying drawing 4, the Moissanite sample of this diamond film coating has no difference in its degree of transparency and brilliance (fire color) and uncoated Moissanite (rough stone) under the naked eye or the low-magnification optical microscope photograph of illustration.

Referring to accompanying drawing 5, it can be seen in the high magnification (30,000 times) photo of the field emission scanning electron microscope that the diamond film on the surface of the diamond film coating Moissanite shown in Figure 4 is very uniform and dense, showing obvious diamond (111) microscopic facets Features, the average grain size is about 80-100nm, and the surface roughness is less than Ra10nm.

With reference to accompanying drawing 6, the small-angle X-ray diffraction spectrum of diamond film coating moissanite surface, visible sharp (111) and (220) diamond diffraction peaks. It shows that what is shown in Fig. 5 is indeed a polycrystalline diamond film.

With reference to accompanying drawing 7, left side: Adopt 5 micron and 1 micron mixed diamond powder ultrasonic grinding 2 hours pretreatment nucleation method and two-stage method (nucleation and growth) to prepare the surface morphology of diamond film coating Moissanite. Discrete large-sized grains appear, and the fire color of the coated Moissanite becomes poor; Right: The surface morphology of the diamond film-coated Moissanite grown directly after cleaning without any pretreatment. The uniformity of the diamond film is very poor, the grain size is very large, and it is not dense, and the Moissanite sample is completely devitrified after deposition (see accompanying drawing 1). It illustrates the superiority of the present invention in adopting the nano-diamond suspension to carry out ultra-high-density diamond nucleation.

Referring to accompanying drawing 8, the Vickers hardness indentation photograph of diamond film coating Moissanite. The HVT-100 microhardness tester produced by Shanghai Lianer Equipment Co., Ltd. was used for testing. Standard diamond pyramid indenter is used. The load P is 0.025kg (0.245N), and the holding time is 10 seconds. Test 10 points for each sample, measure the average diagonal length of the diamond film-coated Moissanite Vickers hardness indentation with a laser confocal microscope, and calculate the Vickers hardness according to the formula: Hv=1854.4P/a ² . The microscale in the figure is 4 μm. The Vickers hardness calculated according to the indentation measurement data shown in the figure is as high as 117GPa, the average hardness calculated according to 10 test points is 84±7GPa, and the diamond hardness is 80-110GPa. The diamond film-coated moissanite prepared by the technology of the invention has reached the hardness of diamond.

Referring to accompanying drawing 9, the scratch resistance ability of diamond film coating moissanite. The scratch tester is used for testing, single crystal diamond stylus, the maximum scribing pressure is 20N, the scribing distance is 2mm, and the acoustic emission signal is recorded while scratching. (a) Uncoated sample (rough stone): The acoustic emission signal begins to appear at about 8N (the signal at 3N is the noise when the screw accidentally lands). The optical microscope image shows that the scribe needle has been carved into the moissanite, forming obvious grooves, showing many discontinuous lateral cracks on both sides of the grooves, corresponding to a series of discontinuous acoustic emission peaks on the acoustic emission spectrum. (b) Moissanite coated with diamond film; the acoustic emission peak does not appear until it is close to 20N. According to the light microscope photo, the scribing needle has broken the surface of the diamond film at this time, and the diamond film has a brittle fracture, and the fracture is very smooth. It has been rolled up, indicating that the diamond film itself has not a small stress, and it is compressive stress. Therefore, it can be shown through experiments that the moissanite jewelry with a diamond film on the surface is only crushed when the pressure is large enough (close to 20N). Compared with jewelry without diamond coating, its scratch resistance performance is greatly improved.

With reference to the thickness of accompanying drawing 10 diamond film coatings. The thickness of the diamond film coating was measured under a field emission scanning electron microscope using a prefabricated fractured mosaic sample. The diamond film coating thickness measured from the illustrated fracture images is 0.2–0.3 μm.

With reference to accompanying drawing 11, adopt the 6.5mm (1 carat) diamond film coating Moissanite of the present invention's technology batch production. The diameter of the sample stage is 62mm, which can allow 55 grains of 6.5mm (1 carat) diamond film-coated Moissanite to be deposited at one time. It can be seen from Figure 12 that the uniformity of the moissanite ornaments deposited in batches is very good, thanks to the precise control that each grain of moissanite ornaments can be pressed into the conformal hole with exactly the same pressure, thus ensuring Temperature uniformity during deposition of large volumes of moissanite jewelry. This is another advantage of the conformal sample stage of the present invention.

Example 2: Preparation of diamond film-coated Moissanite by microwave plasma CVD diamond film deposition equipment

The domestic 6KW grade stainless steel resonant cavity microwave plasma CVD diamond film deposition system is adopted. The pretreatment process of Moissanite nuclei is exactly the same as that of DC arc plasma jet CVD.

Accompanying drawing 12, the comparison of the fire color of the diamond film-coated Moissanite prepared by the microwave plasma CVD system and the uncoated sample (raw stone). Center position: Uncoated rough, left and right diamond coated samples. Deposition process parameters: power: 3KW; pressure: 4.04KPa; methane concentration: 5%; plasma etching time: 5 minutes; deposition time: 1.5 hours; the sample stage is directly in contact with the microwave plasma ball (immersion deposition). It can be seen that there is no difference in fire color between the diamond film-coated Moissanite prepared by microwave plasma CVD and the uncoated rough. The only difference in the deposition process is that the microwave plasma CVD process does not use a two-stage method (nucleation and growth), but uses a methane concentration (5%) to carry nucleation and growth through to the end.

There is no difference in various properties between the diamond film-coated Moissanite prepared by microwave plasma CVD and the diamond film-coated Moissanite prepared by DC arc plasma CVD.

Although hot-filament CVD can also be used to prepare diamond film-coated moissanite, due to the low temperature of the hot filament and insufficient gas activation, the concentration of atomic hydrogen is very low, which seriously affects the quality of the diamond film. Therefore, it is not recommended.

The above is only an embodiment of the present invention, and does not limit the protection scope of the present invention. Any equivalent structure or equivalent process conversion made by using the content of the description of the present invention, directly or indirectly used in other related technical fields, should be included in this document. inventions within the scope of patent protection.

Claims

A diamond film-coated ornament is characterized in that a layer of diamond film coating is coated on the surface of the moissanite ornament, the average grain size of the diamond film is 50 nanometers to 200 nanometers, the surface roughness is less than 10nm, and the thickness of the diamond film is 0.1-200 nanometers. 0.5 microns.
The diamond film-coated ornament according to claim 1, wherein the diamond film-coated ornament is prepared through the following steps:

1) Ultrasonic grinding pretreatment is carried out to moissanite jewelry in the suspension of nano-diamond powder; The time is 1 hour ∽ 6 hours;

2) Moissanite ornaments are taken out from the nano-diamond powder suspension, and cleaned;

3) Apply a certain force to the moissanite jewelry, and press it into the pre-set inverted conical hole of the pure copper conformal sample stand, so that it forms a close contact with the conical hole, that is, surface contact, and the pressure is 50kgf∽ 250kgf;

4) Place the moissanite jewelry together with the conformal sample stage in a diamond film deposition furnace for plasma treatment, the temperature of the plasma treatment is 700°C∽1000°C, and the time of the plasma treatment is 5 minute ∽ 30 minutes;

5) Introduce methane for in-situ diamond film deposition; diamond film deposition adopts "two-stage method": nucleation stage and growth stage, the concentration of methane in the nucleation stage is 3%∽10%, and the time is 5∽20 minutes; The methane concentration in the growth stage is 0.5%∽2%, and the time is 10 minutes∽120 minutes; the pressure of the deposition furnace is set at 3kPa∽20kPa.
The diamond film coated ornament according to claim 2, characterized in that, in said step 4) and step 5), said plasma treatment and in-situ diamond film deposition adopt DC arc plasma jet CVD or microwave plasma CVD.
According to claim 1, 2 or 3 described diamond film coating jewelry, it is characterized in that, described Moissanite jewelry adopts nano-diamond suspension to carry out ultrasonic grinding pretreatment; The diamond particle size in described nano-diamond suspension is 5 nanometers Between 200 nanometers, the concentration of the nano-diamond particles is 5%-20%, and the ultrasonic grinding pretreatment time is 1 hour∽6 hours.
The diamond film-coated ornament according to claim 1, 2 or 3, wherein the pure copper conformal sample stage has an inverted conical conformal hole, and its cone angle is slightly smaller than the inverted pyramid at the pavilion of the moissanite ornament The cone angle is 0°∽-2°. When in use, a certain force is applied to press the moissanite jewelry into the inverted conical conformal hole of the conformal sample stand, forcing the conical hole to undergo plastic deformation. The edges and corners of the moissanite jewelry pavilion on it form surface contact.
A method for preparing a diamond film coating on the surface of an ornament, characterized in that the diamond film-coated ornament is prepared through the following steps:

1) Ultrasonic grinding pretreatment is carried out to moissanite jewelry in the suspension of nano-diamond powder; The time is 1 hour ∽ 6 hours;

2) Moissanite ornaments are taken out from the nano-diamond powder suspension, and cleaned;

3) Apply a certain force to the moissanite jewelry, and press it into the pre-set inverted conical hole of the pure copper conformal sample stand, so that it forms a close contact with the conical hole, that is, surface contact, and the pressure is 50kgf∽ 250kgf;

4) Place the moissanite jewelry together with the conformal sample stage in a diamond film deposition furnace for plasma treatment, the temperature of the plasma treatment is 700°C∽1000°C, and the time of the plasma treatment is 5 minute ∽ 30 minutes;

5) Introduce methane for in-situ diamond film deposition; diamond film deposition adopts "two-stage method": nucleation stage and growth stage, the concentration of methane in the nucleation stage is 3%∽10%, and the time is 5∽20 minutes; The methane concentration in the growth stage is 0.5%∽2%, and the time is 10 minutes∽120 minutes; the pressure of the deposition furnace is set at 3kPa∽20kPa.
The method according to claim 6, characterized in that, in the step 4) and step 5), the plasma treatment and the in-situ diamond film deposition adopt DC arc plasma jet CVD or microwave plasma CVD.
The method according to claim 6 or 7, wherein the moissanite jewelry adopts a nano-diamond suspension for ultrasonic grinding pretreatment; the diamond particle size in the nano-diamond suspension is between 5 nanometers and 200 nanometers, The concentration of the nano-diamond particles is 5%-20%, and the ultrasonic grinding pretreatment time is 1 hour∽6 hours.
The method according to claim 6 or 7, wherein the pure copper conformal sample stage has an inverted conical conformal hole, and its cone angle is slightly smaller than the cone angle of the Moissanite jewelry pavilion inverted pyramid, and the deviation is 0°∽-2°, apply a certain force during use to press the moissanite jewelry into the inverted conical conformal hole of the conformal sample stand, forcing the conical hole to undergo plastic deformation, and the moissanite placed on it The corners and corners of the ornament pavilion form surface contact.