Method for producing ceramic part, in particular synthetic diamond

Abstract

The invention relates to a method for manufacturing a ceramic part from a sample of ceramic powder, comprising: heating said sample to a predetermined minimum temperature, generating and emitting a plurality of acoustic waves by a plurality of acoustic wave generators towards a focusing system, said plurality of acoustic waves together generating a sound intensity Ie at the input of said focusing system, focusing the plurality of acoustic waves in an acoustic focal region within the sample by the focusing system, the focusing system defining a product factor M, the focused plurality of acoustic waves together generating a minimum sound intensity at at least a portion of the acoustic focal region, the minimum sound intensity being at least M x Ie, and combining the minimum heating temperature applied to the sample of ceramic powder sufficient to sinter the ceramic powder in the portion of the acoustic focal region.

Description

Technical Field

[0001] This invention relates to the manufacture of a ceramic component, particularly the manufacture of diamond.

[0002] The present invention relates in particular to a method for manufacturing a ceramic component by sintering, preferably to a method for manufacturing synthetic diamond, and an apparatus for carrying out the method. Background Technology

[0003] Ceramic components manufactured by sintering are increasingly used in industry, especially due to their electronic, mechanical, optical, thermal, or chemical properties.

[0004] Conventional sintering is a process involving heating a powder of a selected material (such as alumina or zirconium oxide) onto a ceramic substrate. Heating causes the powder grains to form chemical bonds, thus creating a ceramic body. The required temperatures typically exceed 1500°C, and the heating time is on the order of several hours (with a core temperature increase of 10°C per minute). A major drawback of conventional sintering is that it produces ceramic parts with grain sizes ranging from 10 to 100 µm, resulting in hard but low mechanical strength. In fact, the grain size of a mechanical component is one of the parameters determining its mechanical strength. The smaller the grain size, the higher the mechanical strength of the component.

[0005] In the course of the 20th century, traditional sintering was improved, with powder heating rates reaching up to 200°C per minute at the core. This is known as flash sintering (spark plasma sintering). Flash sintering involves placing ceramic powder into a mold, typically made of graphite, and, if the material is conductive, passing a high-intensity direct current or alternating current through the mold and into the powder. This innovation made it possible to reduce sintering time to approximately 10 minutes, thereby limiting the growth of powder grains and promoting the formation of chemical bonds between them. This advantage enabled the production of mechanical parts with grain sizes on the order of 1µm by heating to temperatures exceeding 1200°C.

[0006] One of the drawbacks of flash sintering is the requirement for relatively high heating temperatures. This limits the application of metastable materials at ambient temperature and pressure in the manufacture of mechanical parts. For example, diamond is stable at ambient temperature and pressure, but it reverts to graphite when heated above 800°C in an oxygen atmosphere or above 1700°C in an inert gas atmosphere or vacuum.

[0007] In the early 21st century, flash sintering technology was improved by compressing powder under pressures exceeding several hundred MPa. Increasing such pressure in flash sintering not only makes it possible to sinter metastable materials under ambient pressure but also lowers the temperature required for powder sintering, ranging from 500 to 1000°C depending on the material, and thus further reduces grain growth during the sintering process. Mechanical parts with grain sizes smaller than 100 nanometers can be obtained in approximately ten minutes. It is also possible to sinter nanodiamond powder at 5 GPa and 1500°C to obtain polycrystalline diamond mechanical parts with grain sizes between 10 and 100 nanometers.

[0008] One of the main drawbacks of high-pressure flash sintering is the impossibility of creating complex shapes during the sintering process. Indeed, the current apparatus used to achieve pressures exceeding GPa severely limits the shape of the sintering molds.

[0009] In order to manufacture synthetic diamond ceramic components, there are other techniques available besides high-pressure flash sintering of diamond powder.

[0010] One such technique is high-pressure, high-temperature (HPHT). This technique involves placing a carbon sample, such as graphite, into a sealed container and subjecting it to a high temperature on the order of approximately 1500°C and a high pressure on the order of approximately 15 GPa. By adding a catalyst, such as a transition metal like nickel or cobalt, the temperature is reduced to 1000°C and the pressure to 6 GPa. Similarly, HPHT can sinter diamond particles, but uses graphite powder instead of diamond powder. In this case, the graphite powder is compressed to above 7 GPa and heated to above 2000°C. The powder then undergoes a series of phase changes and sintering steps to form a diamond particle.

[0011] Another technique is chemical vapor deposition (CVD). A diamond sample is placed in a vacuum chamber.

[0012] Hydrogen-containing gas is introduced into the vacuum chamber. The gas is then ionized by a microwave discharge, creating a plasma. The plasma-generated material gradually adheres to the substrate, forming an object.

[0013] The main disadvantages of these two technologies are: Precisely controlling the spatial location suitable for diamond formation is extremely difficult, if not impossible; Restricting the diamond growth direction: For HPHT technology, the direction is imposed by the compression mode; for CVD technology, the direction is perpendicular to the substrate.

[0014] Another technology only produces synthetic diamond powder, relying on the principle of dynamic compression to convert graphite into diamond.

[0015] In the dynamic compression-induced graphite-diamond conversion technique, the conversion process is not achieved through diffusion as in the high-temperature, high-pressure (HPHT) technique; that is, the conversion process is not caused by temperature-induced atomic diffusion. The transformation is martensitic, i.e., caused by local deformation of the crystal lattice, as described by Christian et al. in Journal de Physique IV, Vol. 5, C8, December 1995, and confirmed by numerous experiments since the early 1990s, especially those conducted by Erskine et al. in Journal of Applied Physics, Vol. 71, No. 10, 1992, Kraus et al. in Nature Communications, Vol. 7, No. 10970, 2016, and Volt et al. in Journal of Applied Physics, Vol. 125, No. 245902, 2019.

[0016] This technique is based on, for example, the use of shock waves. For instance, a shock wave is generated by projecting a metal foil onto a graphite sample. In the literature, shock waves are often referred to as those generated by an explosion. Shock waves can also be generated by laser ablation. This technique has many drawbacks, particularly that creating these shocks partially destroys the graphite sample, and the duration of these shocks is very limited, on the order of microseconds. The resulting diamond is only in the form of nanocrystals or microcrystals. Summary of the Invention

[0017] The present invention aims to overcome the shortcomings of solutions proposed in the prior art, especially those listed above.

[0018] Therefore, the present invention proposes a method for manufacturing a ceramic component from a sample of ceramic powder, comprising: The ceramic powder sample is heated to a predetermined minimum temperature using a heating system, and then... Multiple sound waves are generated and emitted toward a focusing system by multiple sound wave generators. Each sound wave generator is configured to emit a sound wave with a frequency f between 1 MHz and 100 MHz. The sound waves generate a sound intensity I at the input of the focusing system. e , The focusing system focuses the multiple acoustic waves into a single acoustic focal region within the ceramic powder sample, and the focusing system defines a multiplicative factor M.

[0019] The focused plurality of sound waves are generated together in at least a portion of the acoustic focal domain, forming a sum of at least M x I. eA minimum sound intensity, which, combined with the minimum heating temperature applied to the sample of the ceramic powder, is sufficient to sinter the ceramic powder in the portion of the acoustic focal zone.

[0020] The term "ceramic" refers to so-called technical ceramics. Technical ceramics include: Ceramic oxides are mainly composed of metal oxides such as zirconium oxide or aluminum oxide. Non-oxide ceramics are materials based on carbon, nitride, and silica compounds, such as silicon carbide, tungsten carbide, or aluminum nitride. Silicate ceramics are mainly made by combining raw materials with aluminum oxides such as aluminum silicate.

[0021] The method according to the invention advantageously heats a ceramic powder to a predefined minimum temperature while simultaneously compressing it locally to a pressure, allowing the ceramic powder to be sintered.

[0022] This process clearly shows that the sample was heated before the multiple sound wave generators generated and emitted the multiple sound waves. The multiple sound waves emitted by the multiple sound wave generators did not heat the sample.

[0023] The predefined minimum temperature is preferably higher than the sintering temperature of the selected ceramic powder. The sintering temperature corresponds to the minimum temperature required to sinter the powder under a given pressure. The higher the applied pressure, the lower the sintering temperature.

[0024] As is well known, sound pressure can be expressed as a function of sound intensity. For a given material initially subjected to ambient temperature and pressure, each sound intensity value corresponds to a pressure. Therefore, for the same powder, given that pressure is a function of sound intensity and the minimum temperature required for sintering is a function of pressure, it is possible to deduce that the minimum temperature required for sintering is a function of sound intensity.

[0025] Therefore, depending on the ceramic powder used in the method according to the invention, the heating temperature to be applied advantageously enables the powder to be sintered in at least a portion of the acoustic domain.

[0026] In other words, the sintering temperature of a ceramic powder is a function of the sound intensity generated within at least a portion of the acoustic focal region. The sound intensity and sintering temperature required to sinter a ceramic powder depend on the ceramic powder used.

[0027] The sintering temperature can be derived by prior knowledge of the acoustic intensities produced by the focused acoustic waves within at least a portion of the acoustic focal region. Then, for a given ceramic powder, the method according to the invention can be employed, and a set of values ​​to be applied (acoustic intensity, heating temperature) can be used to enable the sintering of the ceramic powder within at least a portion of the acoustic focal region.

[0028] Therefore, the method of the present invention advantageously enables the sintering of ceramic powder within a portion of the acoustic focal region. Advantageously, the method allows for precise control of the spatial position that satisfies the sintering conditions of the ceramic powder, thereby achieving the sintering of the ceramic powder.

[0029] In one example, according to the method of the present invention, diamond can be obtained by sintering diamond powder, with a sound intensity of 5.10. (11) W. m -2 And a minimum heating temperature of 1360°C is required.

[0030] Depending on the specific implementation mode, the present invention also conforms to the following features, which can be implemented individually or in combination with their respective technical operations.

[0031] In a specific embodiment of the present invention, the ceramic powder is selected from: diamond powder, tungsten carbide powder, silicon nitride powder, fully stabilized zirconia powder, alpha alumina powder, gamma alumina powder, and titanium dioxide powder.

[0032] In a specific embodiment of the invention, the method includes shifting the acoustic focal region in the sample during the emission of multiple sound waves.

[0033] This shift in the acoustic focal region of the sample advantageously allows the sample to be sintered in a selected area, thus producing a portion of powder with a given shape.

[0034] The present invention also relates to an apparatus for carrying out the method according to at least one embodiment thereof, the apparatus comprising: A heating system for heating the sample. Multiple sound wave generators, each configured to generate a sound wave. The multiple sound wave generators and the sample heating system are independent components within the device. A system for focusing multiple sound waves into a focal region in the sample, the focusing system defining a product factor M.

[0035] Each sound wave generator of the device is advantageously configured to emit a sound wave at a frequency of f, preferably between 1 MHz and 100 MHz.

[0036] In a preferred embodiment, all the sound wave generators of the device emit at the same frequency.

[0037] The focusing system is designed and sized to receive all sound waves emitted by the sound wave generator.

[0038] According to specific embodiments, the present invention also satisfies the following features, which can be implemented individually or in combination with their respective technical operations.

[0039] In a specific embodiment, the heating system enables the sample to be heated via the Joule effect or the inductive effect.

[0040] In a specific embodiment, each sound wave generator is a piezoelectric actuator.

[0041] In a specific embodiment, in order to sinter the entire sample, the apparatus includes a component for moving the acoustic focal zone within the sample.

[0042] In an example of an embodiment of the displacement member, the member for shifting the acoustic focal domain in the sample is a member for shifting the focusing system of the acoustic wave and / or a member for shifting the sample and / or a member for shifting the acoustic wave generator and / or a member for changing the phase of the acoustic wave generator.

[0043] The present invention also relates to a method for manufacturing diamond from a sample containing graphite powder, comprising: The graphite powder sample was heated to a predetermined minimum temperature using a heating system, and then... Multiple sound waves are generated and emitted toward a focusing system by multiple sound wave generators. Each sound wave generator is configured to emit a sound wave with a frequency f between 1 MHz and 100 MHz. The multiple sound waves together generate a strong sound at the input of the focusing system. , The focusing system focuses the multiple acoustic waves into a single acoustic focal region within the graphite powder sample, and the focusing system defines a product factor M. The focused plurality of sound waves together generate a sound intensity at least equal to M x I in at least a portion of the acoustic focal region. e = 1.10 12 Wm -2 This corresponds to a minimum sound intensity, and is sufficient to: In the first stage, a phase change from graphite powder to diamond powder is achieved, then... In a second stage, the diamond powder is sintered in conjunction with the minimum heating temperature applied to the sample.

[0044] In order to achieve a phase transition from graphite to diamond in the acoustic focal region, the sound intensity must be sufficient to: The sound pressure level reached exceeds a sufficiently low minimum pressure, making diamond more stable than graphite. During the duration of the sound wave emission, the kinetic energy of the atoms is sufficient to disrupt the metastable state of the graphite.

[0045] When the sound intensity produced by the acoustic focal region is at least equal to 1.10. 12 Wm -2 The duration of the emitted sound intensity then determines the percentage of graphite converted to diamond within the acoustic focal region. In other words, for a given sound intensity emitted within the acoustic focal region, the longer the duration of the emitted sound intensity, the greater the percentage of graphite converted to diamond within the acoustic focal region. Furthermore, for a desired percentage of graphite converted to diamond, the greater the emitted sound intensity, the shorter the duration of the emitted sound intensity at the acoustic focal region.

[0046] Therefore, depending on the sound intensity generated in the acoustic focal region, it is preferable to emit multiple sound waves of at least a minimum duration, thereby allowing graphite to be converted into diamond in the acoustic focal region to reach a desired predefined percentage.

[0047] This process clearly shows that the sample is heated before the multiple sound wave generators generate and emit the multiple sound waves. The sample is not heated by the multiple sound waves emitted by the multiple sound wave generators. This is achieved by heating the sample at a predefined minimum temperature when the sound intensity reaches 1.10. 12 Wm -2 Heating the sample in parallel within a portion of the acoustic focal region can advantageously densify the resulting diamond powder by sintering.

[0048] The sintering temperature of graphite powder depends on the acoustic intensity generated at least a portion of the acoustic focal region.

[0049] The sintering temperature can be derived by prior knowledge of the acoustic intensities produced by the focused multiple sound waves within at least a portion of the acoustic focal region. The graphite powder can then be applied using the method according to the invention, with a set of values ​​to be applied (acoustic intensity, heating temperature) so that sintering of the graphite powder can be performed within at least a portion of the acoustic focal region.

[0050] The present invention also relates to a method for manufacturing diamond from a sample containing amorphous carbon powder, comprising: The sample of amorphous carbon powder was heated to a predetermined minimum temperature, and then... Multiple sound waves are generated and emitted toward a focusing system by multiple sound wave generators. Each sound wave generator is configured to emit a sound wave with a frequency f between 1 MHz and 100 MHz. The multiple sound waves together generate a strong sound at the input of the focusing system. , The focusing system focuses the multiple acoustic waves into a single acoustic focal domain within the amorphous carbon powder sample. The focusing system defines a product factor M. The focused plurality of sound waves together generate a sound intensity at least equal to M x I in at least a portion of the acoustic focal region. e = 2.1.10 12 Wm -2 This corresponds to a minimum sound intensity, and is sufficient to: In the first stage, a phase change from amorphous carbon powder to diamond powder is achieved, then... In a second stage, the diamond powder is sintered in conjunction with the minimum heating temperature applied to the sample.

[0051] The term "amorphous carbon" refers to allotropes of carbon, including sp. 2 Atomic bonds (same type as graphite) and sp 3 It is a mixture of atomic bonds (similar to those in diamond) and contains a possible concentration of hydrogen atoms. The distribution of different bond types is random. This distribution does not necessarily exhibit any order on small or large scales.

[0052] Advantageously, amorphous carbon, which does not contain hydrogen atoms, typically has a sp2 ratio between 40% and 90%. 3 Hybridization rate.

[0053] In order to achieve a phase change from amorphous carbon to diamond in the acoustic focal region, the acoustic intensity must be sufficient to: The sound pressure level reached exceeds a minimum pressure sufficient to make diamond more stable than graphite. During the duration of the sound wave emission, the kinetic energy of the atoms is sufficient to disrupt the metastable state of the graphite.

[0054] When the sound intensity produced by the acoustic focal region is at least equal to 2, 1.10 12 Wm -2 Wm -2 The duration of the acoustic emission then determines the percentage of amorphous carbon converted into diamond within the acoustic focal region. In other words, for a given acoustic intensity emitted within the acoustic focal region, the longer the duration of the acoustic emission, the greater the percentage of amorphous carbon converted into diamond within the acoustic focal region. Furthermore, for a desired percentage of amorphous carbon converted into diamond, the greater the emitted acoustic intensity, the shorter the duration of the acoustic emission at the acoustic focal region.

[0055] Therefore, depending on the acoustic intensity generated in the acoustic focal region, multiple sound waves of at least a minimum duration are preferentially emitted, thereby allowing amorphous carbon in the acoustic focal region to be converted into diamond to a desired predefined percentage.

[0056] This process clearly shows that the sample is heated before the multiple sound wave generators generate and emit the multiple sound waves. The sample is not heated by the multiple sound waves emitted by the multiple sound wave generators.

[0057] By achieving a sound intensity of 2.1.10 at a predefined minimum temperature. 12 Wm -2 Wm -2 The sample is heated in parallel within a portion of the acoustic focal region, and the resulting diamond powder is densified by sintering.

[0058] The sintering temperature of amorphous carbon powder depends on the acoustic intensity generated at least a portion of the acoustic domain.

[0059] The sintering temperature can be derived by prior knowledge of the acoustic intensities produced by the focused multiple acoustic waves within at least a portion of the acoustic focal region. The amorphous carbon powder can then be applied using the method according to the invention, with a set of values ​​to be applied (acoustic intensity, heating temperature) to enable sintering within at least a portion of the acoustic focal region.

[0060] The present invention also relates to an apparatus for carrying out a method of manufacturing diamond from a sample containing graphite powder or a sample containing amorphous carbon powder, the apparatus comprising: A heating system is used to heat the sample. Multiple sound wave generators, each configured to generate a sound wave. The multiple sound wave generators and the sample heating system are independent components within the device. A system for focusing the plurality of acoustic waves in an acoustic focal domain within the sample, wherein the focusing system defines the product factor M.

[0061] Each sound wave generator of the device is advantageously configured to emit a sound wave at a frequency f, which is preferably between 1 MHz and 100 MHz.

[0062] In a preferred embodiment, all the sound wave generators of the device emit at the same frequency.

[0063] The focusing system is designed and sized to receive all sound waves emitted by the sound wave generator.

[0064] According to specific embodiments, the present invention also satisfies the following features, which can be implemented individually or in combination with their respective technical operations.

[0065] In a specific embodiment, the heating system enables the sample to be heated via the Joule effect or induction effect.

[0066] In a specific embodiment, each sound wave generator is a piezoelectric actuator.

[0067] In a specific embodiment, to make the diamond credible, the device includes a component for moving the acoustic focal region in the sample.

[0068] In an example of an embodiment of the displacement member, the member for shifting the acoustic focal domain in the sample is a member for shifting the focusing system of the acoustic wave and / or a member for shifting the sample and / or a member for shifting the acoustic wave generator and / or a member for changing the phase of the acoustic wave generator. Attached Figure Description

[0069] The invention can be better understood by reading the following description, which is given by way of example only and is not limited thereto, and reference is made to the following figures: Figure 1 A perspective view shows an apparatus particularly suitable for the ceramic manufacturing process according to the present invention; Figure 2 Showing Figure 1 A perspective view of half of the device shown; Figure 3 Showing Figure 2 A cross-section of the device shown; Figure 4 Showing Figure 3 An enlarged view of region III, illustrating an example of a piezoelectric actuator; Figure 5A graph showing the sintering temperature of different types of ceramic powder as a function of pressure; Figure 6 A graph showing the sintering temperature of different types of ceramic powder as a function of sound intensity; Figure 7 A model curve showing the induced pressure of graphite and amorphous carbon as a function of sound intensity is displayed. Figure 8 A modeling curve showing the kinetic energy of graphite and amorphous carbon as a function of sound intensity is displayed; Figure 9 A graph showing the time required to emit a sound wave as a function of the intensity of the sound wave is used to reproduce the conditions sufficient to achieve a 99% phase change in a diamond-graphite sample and a diamond-amorphous carbon sample.

[0070] In these accompanying drawings, the same reference numerals denote the same or similar elements. Furthermore, for clarity, unless otherwise stated, the drawings are not drawn to scale. Detailed Implementation

[0071] Figures 1 to 4 A device 100 is illustrated. This device 100 is suitable for performing: A process for manufacturing a ceramic component from a sample 50 of ceramic powder; this process is referred to below as the first process; A process for producing a diamond from a sample 50 containing graphite or amorphous carbon powder; this process is referred to below as the second process.

[0072] In the case of the first process, sample 50 contains only ceramic powder.

[0073] The ceramic powder is preferably selected from tungsten carbide, silicon nitride, fully stabilized zirconium oxide (FSZ), α-alumina, γ-alumina, titanium dioxide, and diamond.

[0074] In the second process, sample 50 may contain a diamond seed and graphite or amorphous carbon powder. Preferably, sample 50 contains only graphite or amorphous carbon powder.

[0075] Preferably, the ceramic, graphite, or amorphous carbon powder is composed of nano-sized grains. These grains are separated from each other.

[0076] In the remainder of this specification, "grains" refers to particles whose maximum size to minimum size ratio is preferably less than or equal to 5. Grains can be spherical, cubic, or other geometric shapes.

[0077] The term "size" is used to describe grains, referring to the maximum size of these grains.

[0078] The term "nanometric" also refers to a size greater than or equal to 1 nanometer and less than 1000 nanometers.

[0079] like Figures 1 to 4 As shown, the device 100 includes: Multiple sound wave generators 10, A system 20 for focusing the plurality of sound waves into a sonic focal region in the sample 50.

[0080] Preferably, such as Figure 3 and Figure 4 As shown, the sound wave generator 10 is attached to the focusing system 20.

[0081] The sample 50, located downstream of the focusing system 20, is placed in a medium called the propagation medium 40. The sample 50 is held in place in the propagation medium 40. For example, a container 70 placed in the propagation medium 40 is used to contain the sample 50.

[0082] In one embodiment, the container 70 is in the form of a tube, with at least one of its two ends closed, preferably both ends are closed.

[0083] Each sound wave generator 10 of the device 100 is configured to generate and emit a sound wave at a frequency of f, which is preferably between 1 MHz and 100 MHz. In a preferred embodiment, all the sound wave generators 10 of the device 100 emit at the same frequency.

[0084] Preferably, the multiple sound waves emitted by the generator 10 are synchronized.

[0085] In another non-limiting example, some of the sound wave generators 10 of the device 100 (e.g., half) emit at the same frequency f1, while the other sound wave generators 10 of the device 100 emit at the same frequency f2, different from f1.

[0086] Each sound wave generator 10 of the device 100 is configured to generate and transmit a sound wave with power P.

[0087] Preferably, the plurality of sound wave generators 10 are similar to each other.

[0088] In a preferred embodiment, the sound wave generators 10 are all piezoelectric actuators. A piezoelectric actuator converts an electrical signal into a sound signal with a given power.

[0089] In a preferred embodiment of a piezoelectric actuator, the piezoelectric actuator comprises a continuous stack of layers: At least one impedance mismatch layer11 At least one piezoelectric element 12, At least one impedance matching layer.13.

[0090] Therefore, the at least one piezoelectric element 12 is located between the at least one impedance mismatch layer 11 and the at least one impedance matching layer 13. The at least one impedance matching layer 13, in part, is located between the at least one piezoelectric element 12 and the focusing system 20.

[0091] exist Figure 4 In the non-limiting example shown, the piezoelectric actuator 10 includes two impedance mismatch layers 11, a piezoelectric element 12, and an impedance matching layer 13.

[0092] The frequency of the electrical signal applied to the terminals of the at least one piezoelectric element 12 determines the frequency of the generated sound wave. For example, this frequency may correspond to the resonant frequency of the at least one piezoelectric element 12 to maximize the conversion rate of the electrical signal into a sound wave.

[0093] The at least one impedance matching layer 13 is preferably configured to maximize the transmission of acoustic waves from the at least one piezoelectric element 12 to the focusing system 20.

[0094] The at least one impedance mismatch layer 11 is preferably configured to minimize the transmission of acoustic waves from the device 100.

[0095] The plurality of piezoelectric actuators 10 are preferably arranged and fixedly held in a component referred to as a cylinder 15.

[0096] The cylinder contains a plurality of orifices 151, each designed to receive a piezoelectric actuator. These orifices extend through the thickness of the cylinder.

[0097] Each piezoelectric actuator 10 is arranged in a hole 151 in the barrel 15 such that the at least one impedance matching layer 13 faces the focusing system 20.

[0098] The pores of the cylinder 15 are preferably parallel to each other. Since the piezoelectric actuators 10 are arranged parallel to each other, the sound waves leaving the piezoelectric actuators propagate in the same direction.

[0099] The pores are preferably arranged in the cylinder 15 such that the piezoelectric actuators 10 are equidistant from each other.

[0100] The components of the piezoelectric actuator 10 are, for example, cylindrical. The plurality of holes 151 in the cylinder 15 are cylindrical.

[0101] Preferably, a prestressed bolt 16 is configured to hold and compress a piezoelectric actuator 10 within an orifice 151 of the cylinder 15. This compression of the piezoelectric actuator helps to maximize the conversion rate of electrical energy to acoustic energy. Each prestressed bolt 16 is preferably located on the impedance mismatch layer 11.

[0102] The device 100 includes a plurality of prestressed bolts 16, the same number as the plurality of piezoelectric actuators 10.

[0103] Preferably, the device 100 includes a component referred to as a cover 17, which is fixed to the cylinder 15. This cover has a plurality of threaded holes 171 into which the prestressed bolts 16 are screwed.

[0104] The device 100 preferably includes a management unit (not shown in the figure) for the plurality of sound wave generators 10.

[0105] The device 100, preferably the management unit, is configured to control the duration of sound waves emitted by the plurality of sound wave generators 10.

[0106] In one embodiment (not shown in the figure), the management unit includes a power supply and a synchronization unit.

[0107] The power supply is configured to supply power to each acoustic wave generator 10 in the form of a DC signal.

[0108] The synchronization unit is configured to synchronously drive the plurality of acoustic wave generators 10.

[0109] In a non-limiting example, when the plurality of acoustic wave generators 10 are plurality of piezoelectric actuators, the management unit includes: A power supply is configured to provide the power required by each piezoelectric actuator in the form of a DC signal; A synchronization unit, comprising: A first clock, also known as the master clock, is used to drive the piezoelectric actuator from a single time reference; Multiple cascaded clocks control the power supply circuit of each piezoelectric actuator with in-phase signals; A power supply circuit consisting of half-H bridges is used to charge and discharge the piezoelectric actuator.

[0110] As previously mentioned, the device 100 also includes a focusing system 20.

[0111] This focusing system 20 is configured to receive multiple sound waves emitted from the plurality of sound wave generators 10 and focus them onto a single acoustic focal region within the sample 50.

[0112] The acoustic focal zone is a reduced-size region where all sound waves converge.

[0113] The acoustic focal range is preferably smaller than the sample size of 50.

[0114] Preferably, the sample is contained in a tubular container 70 with a diameter of 50 mm and a length of 50 mm. The sample completely fills the container.

[0115] Preferably, the acoustic focal length is less than 1mm x 1mm x 1mm.

[0116] The size of the acoustic focal region is determined by the frequency of the sound wave, the propagation speed of the sound wave in the sample 50, the cross-sectional diameter of the focusing system 20, and the focal length of the focusing system 20. The cross-section refers to a section perpendicular to an axis of symmetry of the focusing system.

[0117] The acoustic focal region typically resembles an ellipsoid with a circular cross-section. The cross-section of the acoustic focal region is a section perpendicular to the direction of propagation of a sound wave located on an axis of symmetry of the focusing system. The ellipsoid is defined by its semi-major axis and semi-minor axis. The semi-major axis corresponds to half the length of the ellipsoid along the direction of propagation of the sound wave on an axis of symmetry of the focusing system. The semi-minor axis corresponds to the radius of the largest cross-section.

[0118] Preferably, the acoustic focal region is an ellipsoid with a circular cross-section, having a major axis between 0.2 mm and 2 mm and a minor axis between 0.05 mm and 1 mm, more preferably between 0.07 mm and 0.75 mm. Higher values ​​are suitable for powders with high sound velocities, such as diamond powder, and lower values ​​are suitable for powders with low sound velocities, such as graphite powder.

[0119] Preferably, the sample is initially positioned such that the acoustic focal region is located within the center of the sample, i.e., such that the center of the ellipsoid coincides with the center of the sample.

[0120] The focal plane of the acoustic focal domain is defined as a transverse plane passing through the center of the acoustic focal domain of the ellipsoid. In other words, the maximum cross-section of the ellipsoid is contained within the focal plane.

[0121] Therefore, the initial positioning of sample 50 is preferably such that the focal plane of the acoustic focal region passes through the center of the sample.

[0122] The focusing system 20 defines a product factor M. This product factor M is defined as the ratio of the cross-sectional area of ​​the input end of the focusing system to the cross-sectional area of ​​the acoustic focal domain in the focal plane. The cross-sectional area of ​​the acoustic focal domain in the focal plane is defined as the cross-section corresponding to the cross-section passing through the center of the ellipsoid.

[0123] The focusing system 20 is designed and sized to receive all sound waves emitted by the plurality of sound wave generators 10.

[0124] The focusing system 20 is configured to have a minimum focal length. A minimum focal length facilitates minimizing the volume of the acoustic focal region, thereby maximizing the sound intensity achieved within the acoustic focal region. In a preferred example, regardless of the powder used, the focal length is approximately 100 millimeters for a focusing system 20 with a diameter of 15 centimeters (cm). The focal length increases with increasing diameter of the focusing system 20.

[0125] Advantageously, the focusing system 20 has a shape adapted to the speed of sound of the propagation medium 40 and its own speed of sound.

[0126] In one embodiment of the focusing system 20, the focusing system is a focusing lens. The focusing lens includes: A first surface 21 is provided for facing the plurality of sound wave generators 10, presenting a planar bearing surface for the plurality of sound wave generators 10. A second surface 22, for facing the sample 50, has a shape that is a function of the sound velocity of the propagation medium 40 and the sound velocity of the focusing lens.

[0127] In this example, the size of the acoustic focal zone, that is, its volume, is determined by the frequency f of the plurality of sound waves, the propagation speed of the sound waves in the selected powder, the diameter of the focusing lens, and the focal length of the focusing lens.

[0128] As a non-limiting example, for a sample 50 in the form of graphite powder, for an acoustic frequency of 20 MHz, the acoustic wave propagates in the graphite, a focusing system has a diameter of 150 mm and a focal length of 100 mm, and the acoustic focal domain can be assimilated into an ellipsoid having a circular cross-section, a semi-major axis of 0.5 mm, and a semi-minor axis of 0.18 mm.

[0129] In another non-limiting example, for a sample in the form of diamond powder, having an acoustic wave frequency of 20 MHz, the acoustic wave propagating in the diamond powder, a focusing system with a diameter of 450 mm and a focal length of 300 mm, the acoustic focal domain can be assimilated into an ellipsoid having a circular cross-section, a semi-major axis of 1.0 mm, and a semi-minor axis of 0.35 mm.

[0130] exist Figure 1 In the example shown, the focusing system 20 is a plano-concavespherical lens. In other words, the first surface 21 is a plane, and the second surface 22 is a concave surface.

[0131] The product factor M of the plano-concave spherical lens is then defined as the ratio of the cross-sectional area of ​​the first surface 21 to the cross-sectional area of ​​the acoustic focal region in the focal plane.

[0132] In one embodiment, the focusing system 20 is arranged and fixed within a cylinder 19. A cylindrical body 15, housing a plurality of acoustic wave generators 10, is located at a first end 191 of the cylinder. A cover plate 18 is located at a second end 192 of the cylinder. The focusing system 20 and the cover plate 18 are separated by the propagation medium 40.

[0133] exist Figure 1 In the non-limiting example shown, the cylinder 19 has a circular cross-section.

[0134] Preferably, the propagation medium 40 is selected to facilitate the propagation of multiple sound waves leaving the focusing system 20 toward the sample 50. The propagation medium 40 is preferably a solid or liquid medium.

[0135] The propagation medium 40 is, for example, water or liquid gallium.

[0136] Preferably, the focusing system 20 is made of a material whose sound wave propagation speed is much higher than that of the propagation medium, in order to minimize the focal length of the focusing system and thus minimize the size of the acoustic focal domain. The focusing system 20 is made of a material having an acoustic impedance close to that of the propagation medium 40, in order to maximize the transmission of multiple sound waves from the focusing system 20 to the propagation medium 40.

[0137] In a preferred embodiment, the focusing system 20 is made of aluminum. The propagation speed of multiple sound waves in aluminum is approximately 6400 ms. -1 The propagation speed in gallium is approximately 2850 ms. -1The acoustic impedance of aluminum is approximately 17 MRayls, as is that of gallium, which allows multiple sound waves to be transmitted 100% from the focusing system 20 to the propagation medium 40.

[0138] The apparatus 100 also includes a heating system (not shown) for the sample 50. The heating system is configured to ensure a uniform heating temperature for the sample 50.

[0139] As can be clearly seen from the description, the heating system of the sample 50 is an additional element in the device 100, and the heating system is a separate and independent element from the plurality of sound wave generators.

[0140] In a first embodiment, the heating system is capable of heating using the Joule effect. For example, the heating system includes two cables, each connected to the container 70 containing the sample 50. The two cables are preferably spaced apart from each other. A high-intensity direct current or alternating current of several volts is applied to the container. The applied current is approximately several kiloamperes. The current flowing through the container causes the sample 50 to heat up.

[0141] Preferably, the container 70 is made of a conductive material, such as graphite.

[0142] Using a graphite container, the sample 50 can be heated to 3000°C.

[0143] In a second embodiment, the heating system is designed for induction heating. The heating system includes, for example, an induction coil wound around the container 70. The container is preferably in a tubular form. Alternating current is applied to the induction coil to generate an induced current in the container 70, thereby heating the container 70 and the sample 50.

[0144] Preferably, the container 70 is made of a conductive material, such as metal.

[0145] Depending on the metal used, the sample 50 can be heated to 1000°C to 1500°C.

[0146] As a reminder, diamond is stable under ambient temperature and pressure, but it will revert to graphite when heated to above 800°C in an oxygen atmosphere, or above 1700°C in an inert atmosphere or vacuum.

[0147] Preferably, if sample 50 is diamond powder, it is immersed in an inert or vacuum atmosphere. Furthermore, the entire apparatus 100 is also immersed in an inert or vacuum atmosphere.

[0148] In the case of other ceramics, there are no restrictions on the atmosphere in which the sample is immersed.

[0149] In a preferred embodiment, not shown in the figures, the apparatus 100 includes a displacement member (not shown) for displacing the acoustic focal region in the sample 50. This displacement member advantageously allows the acoustic focal region to be displaced within the sample to form the ceramic component.

[0150] In one embodiment of a displacement member, the displacement member is configured to displace the sample 50.

[0151] In another embodiment of a displacement member, the displacement member is configured to shift the focusing system 20.

[0152] In another embodiment of a displacement member, the displacement member is configured to displace the plurality of acoustic wave generators 10.

[0153] In a further embodiment of a displacement member, the displacement member is configured to perform phase displacement on the plurality of acoustic wave generators 10.

[0154] The first method will now be described.

[0155] The first process is based on the principle of high-pressure flash sintering. In other words, the first process heats the ceramic powder to a predefined temperature and simultaneously compresses it locally to a certain pressure, causing the ceramic powder to sinter.

[0156] It is well known that the higher the applied pressure, the lower the sintering temperature. As a reminder, the sintering temperature corresponds to the minimum temperature required for powder sintering at a given pressure.

[0157] Using diagrams, Figure 5 The example shows seven curves illustrating the minimum temperature required to sinter powders at different pressure values ​​(in GPa). Each curve is associated with a different type of ceramic powder. Figure 5 The various powders shown include diamond powder, tungsten carbide powder, silicon nitride powder, fully stabilized zirconium oxide powder, α-alumina powder, γ-alumina powder, and titanium dioxide powder.

[0158] The first process involves heating sample 50 to a predetermined temperature.

[0159] The sample is heated to a predetermined minimum temperature. This minimum temperature is preferably higher than the sintering temperature of the selected ceramic powder, which is a function of the pressure applied to the acoustic focal region of the sample 50.

[0160] As an example, such as Figure 5As shown, for a diamond powder, the sintering temperature is 1400°C when the applied pressure is 4 GPa, and the sintering temperature is 1300°C when the applied pressure is 5 GPa.

[0161] The heating is preferably performed by the heating system of the device 100.

[0162] In one embodiment, heating is achieved through the Joule effect by allowing an electric current to flow through the container 70 via multiple cables.

[0163] In another embodiment, heating is achieved through an induction effect, by generating an induced current in the container 70 via an induction coil.

[0164] Once the sample 50 reaches the predetermined minimum temperature, the first process involves the generation and emission of multiple sound waves.

[0165] As can be clearly seen from the description, the step of generating and emitting multiple sound waves is performed after the heating step. The step of generating and emitting multiple sound waves is performed only when the sample 50 is at the predetermined minimum temperature.

[0166] The multiple sound waves are emitted simultaneously over a predetermined duration, preferably over the same duration.

[0167] For example, the duration of each of the multiple sound waves emitted is approximately one hour.

[0168] The plurality of sound waves are preferably generated and emitted by a plurality of sound wave generators 10 controlled by the management unit. The duration of each sound wave emission is controlled by the management unit. Each sound wave generator 10 generates and emits a sound wave of a predetermined power. Preferably, the power generated by each sound wave generator 10 is the same.

[0169] Multiple sound waves together generate a strong sound I at the input of the focusing system 20. e .

[0170] As a reminder, the sound intensity I generated at the input of the focusing system e The power injected into the focusing system 20 is determined by the ratio of the power injected into the focusing system 20 to the cross-sectional area of ​​the input end of the focusing system 20. The power injected into the focusing system 20 is determined by multiplying the number of multiple acoustic generators 10 used by the power produced by one acoustic generator 10 (assuming that all acoustic generators produce the same power).

[0171] Then, the emitted sound waves are focused into an acoustic focal region located within the sample 50. The sound waves are emitted along the direction of the focusing system 20, pass through the focusing system, and converge towards the sample 50 into the acoustic focal region.

[0172] It is easy to understand that within the acoustic focal range, the focused sound wave will produce a sound intensity, which within a certain range corresponds to the sound intensity I at the input of the focusing system. e Multiply by the product factor M of the focusing system. This product factor M is the sound intensity I caused by focusing. e One of the product factors.

[0173] The sound intensity in the focal region is not uniform.

[0174] More precisely, the spatial distribution of sound intensity on a known focal plane is non-uniform, exhibiting an Airy spot pattern. Therefore, on the focal plane, the sound intensity forms a central (circular) point and a series of concentric rings surrounding this central point. The central point concentrates 85% of the sound power. The remaining sound power is distributed in a decreasing manner across the series of concentric rings. The average sound intensity at the central point is 0.85 x M x I. e The sound intensity at 80% of the maximum value at the center point is 2.9 x M x I. e The maximum sound intensity at the center point is 3.7 x M x I. e The maximum sound intensity at the center point is punctual. The spatial distribution of sound intensity on a plane perpendicular to the focal plane is also non-uniform. The sound intensity gradually decreases away from the focal plane.

[0175] For the purposes of this invention, the acoustic focal region corresponds to the center point on the focal plane. Therefore, since the maximum intensity within the acoustic focal region is greatest on the focal plane, the maximum sound intensity within the acoustic focal region is 3.7 x M x I. e .

[0176] According to the present invention, multiple focused sound waves together generate at least M x I in at least a portion of the acoustic focal domain. e A loud bang.

[0177] According to the present invention, in conjunction with the heating temperature applied to the sample 50 of ceramic powder, the acoustic intensity generated in at least a portion of the acoustic focal region must be at least equal to the minimum acoustic intensity sufficient to cause the ceramic powder to sinter in at least a portion of the acoustic focal region.

[0178] As is well known to those skilled in the art, sound pressure can be expressed as a function of sound intensity. For a given material initially subjected to ambient temperature and pressure, each sound intensity value corresponds to a pressure. These sound intensity values ​​have been characterized in great detail through studies of so-called Hugoniot curves, as documented in the book "LASL shock Hugoniot data" published by the University of California Press in 1980.

[0179] Therefore, for the same powder, knowing that pressure is a function of sound intensity and the minimum temperature required for sintering is a function of pressure, it is possible to obtain the minimum temperature required for sintering as a function of sound intensity.

[0180] Figure 6 Four curves are shown as examples, illustrating different sound intensity values ​​(unit: Wm). -2 The minimum temperature required for sintering the powder. Each curve is associated with a different type of ceramic powder. Figure 6 In the non-limiting examples shown, the various powders represented are diamond powder, tungsten carbide powder, silicon nitride powder, and α-alumina powder.

[0181] Therefore, as Figure 6 As shown, a sample of 50 diamond powder heated to a minimum temperature of 1375°C was subjected to a 4.7.10 treatment. 11 Wm - 2 A strong sintering sound is all it takes to sinter diamond powder, whereas sintering the same powder without pressure requires temperatures exceeding 2000°C. Similarly, a sample of 50 α-alumina powder heated to a minimum temperature of 840°C was subjected to 4.9.10... 10 Wm - 2 With a loud screwing sound, α-alumina powder can be sintered, while sintering the same powder without pressure requires a temperature of 1100°C.

[0182] Depending on the ceramic powder used in the first process, a pair of values ​​to be applied (sound intensity, heating temperature) can be associated, which is beneficial for sintering the powder in at least a portion of the acoustic domain.

[0183] According to the first process of the present invention, diamond can be obtained by sintering diamond powder, with a sound intensity of 5.10. 11 Wm -2 And a minimum heating temperature of 1360°C is required.

[0184] According to the first process of the present invention, diamond can be obtained by sintering diamond powder, from: The intensity of a single sound is 1.10. 11 Wm -2 And a minimum heating temperature of 1700℃, The intensity of one beat is 5.10. 13 Wm -2 And a minimum heating temperature of 1000℃.

[0185] Generally, in order to obtain diamond from diamond powder, the sound intensity can be increased from 1.10. 11 Wm -2 Change to 5.10 13 Wm -2The minimum heating temperature can be varied from 1700°C to 1000°C.

[0186] To prevent diamond from graphitizing, the minimum heating temperature should not exceed 1700°C in an inert gas atmosphere or under vacuum.

[0187] Further examples are described below in a non-restrictive manner.

[0188] According to the first process of the present invention, an oxide can be obtained by sintering oxide powder, from: The intensity of one beat is 5.10. 8 Wm -2 And a minimum heating temperature of 1700℃, The intensity of a single sound is 1.10. 12 Wm -2 And a minimum heating temperature of 500℃.

[0189] Generally, in order to obtain an oxide by sintering oxide powder, the acoustic intensity can be from 5.10. 8 Wm -2 Change to version 1.10 12 Wm -2 And a minimum heating temperature that can be varied from 1700°C to 500°C.

[0190] Oxides include aluminum oxide or bauxite, silicon oxide, titanium dioxide, zinc oxide, zirconium oxide or zirconium oxide, molybdenum oxide or tungsten oxide.

[0191] According to the first process of the present invention, a carbide can be obtained by sintering carbide powder, from: The intensity of one beat is 5.10. 8 Wm -2 And a minimum heating temperature of 2200℃, The intensity of one beat is 5.10. 12 Wm -2 And a minimum heating temperature of 1000℃.

[0192] Generally, in order to obtain a carbide by sintering carbide powder, the sound intensity can be from 5.10. 8 Wm -2 Change to 5.10 12 Wm -2 And a minimum heating temperature that can be varied from 2200°C to 1000°C.

[0193] Carbides include boron carbide, silicon carbide, titanium carbide, zirconium carbide, molybdenum carbide, and tungsten carbide.

[0194] According to the first process of the present invention, a nitride, a boride, or a silicide can be obtained by sintering nitride, boride, or silicide powder, respectively, from: A sound intensity of 5.10 8 Wm -2 And a minimum heating temperature of 2000℃, The intensity of one beat is 5.10. 12 Wm -2 And a minimum heating temperature of 700℃.

[0195] Generally, in order to obtain a carbide by sintering carbide powder, the sound intensity can be from 5.10. 8 Wm -2 Change to 5.10 12 Wm -2 And a minimum heating temperature that can be varied from 2200°C to 700°C.

[0196] Carbides include boron nitride, aluminum nitride, silicon nitride, titanium nitride, zirconium nitride, molybdenum nitride, tungsten nitride, aluminum boride, titanium boride, zirconium boride, or molybdenum silicide in hexagonal or cubic form.

[0197] Example 1: A simulation was performed to replicate 100 devices on a small scale and determine a desired volume of the acoustic focal region.

[0198] In this simulation, the focusing system 20 is a plano-concave spherical lens. The dimensions of the plano-concave spherical lens are as follows: the diameter of the first surface 21 is 7.5 mm, its center thickness is 2 mm, and the radius of curvature of the second surface 22 is 4 mm. The plano-concave spherical lens is made of aluminum.

[0199] 190 piezoelectric actuators, each with a diameter of 0.5 mm, are evenly distributed opposite the first surface 21 of the plano-concave spherical lens. The 190 piezoelectric actuators are bonded to the first surface 21 of the plano-concave spherical lens. Each piezoelectric actuator emits a sound wave with a frequency of 20 MHz. Each piezoelectric actuator generates a power of 1 W.

[0200] The following values ​​correspond to a sample of diamond powder. For ease of comparison, the values ​​given in parentheses correspond to a sample of α-alumina powder.

[0201] Simulation results show that, within the acoustic focal domain, its volume can be assimilated into an ellipsoid with a circular cross-section, a semi-major axis of 0.92 mm (0.87 mm respectively), and a semi-minor axis of 0.33 mm (0.31 mm respectively).

[0202] Through this simulation, we can derive the product factor M of the plano-concave spherical lens. In this case, the product factor M is the ratio of the entry cross-section of the plano-concave spherical lens to the cross-section of the acoustic focal region on the focal plane. Therefore, the product factor M is 1.3.10. 2 (respectively 1.4.10) 2 ).

[0203] As is well known, as long as the angular aperture of the plano-concave spherical lens remains constant, increasing its size will not affect the size of the acoustic focal region. As a reminder, the angular aperture is proportional to the ratio of the diameter of the first surface of the plano-concave spherical lens to the radius of curvature of the second surface.

[0204] Therefore, a plano-concave spherical lens, having a first facet with a diameter of 450 mm (150 mm in total) and a second facet with a radius of curvature of 240 mm (80 mm in total), can maintain the acoustic focal domain dimensions obtained in the simulation. It is well known that lens thickness has no effect on the angular aperture. The lens thickness is set to 1 cm to minimize the propagation distance of the sound waves while maintaining lens strength.

[0205] At these dimensions, the product factor M of the plano-concave spherical lens is 4.7.10. 5 (5.7.10 respectively) 4 ).

[0206] To cover the first surface of this plano-concave spherical lens, we can use, for example, 1600 (150 each) piezoelectric actuators with a diameter of 10 mm, or 10000 (940 each) piezoelectric actuators with a diameter of 4 mm, or 100 (10 each) piezoelectric actuators with a diameter of 40 mm.

[0207] If we choose 1600 piezoelectric actuators (150 of each) with a diameter of 10 mm as an example, and each actuator generates a sound wave with a power of 100 W, then multiple sound waves will together generate 1.0.10 at the input of the lens. 6 Wm -2 (8.5.10 respectively) 5 Wm -2 A loud I e .

[0208] It should be noted that sound intensity I e This corresponds to the ratio of the power injected into the plano-concave spherical lens to the cross-sectional area of ​​the first surface of the plano-concave spherical lens. The power injected into the lens corresponds to the number of piezoelectric actuators used multiplied by the power generated by each piezoelectric actuator.

[0209] It is worth noting that the same acoustic intensity can be obtained at the entrance of the plano-concave spherical lens in either of the configurations using 10,000 piezoelectric actuators (940 each) with a diameter of 4 mm and each actuator producing 15.90 W of power, or 100 piezoelectric actuators (10 each) with a diameter of 40 mm and each actuator producing 1590 W of power.

[0210] In a configuration with 1600 (150) piezoelectric actuators, this gives an average sound intensity of 4.010 in the focal plane of the acoustic focal region. 11 Wm -2 (Corresponding to 0.85 x 4.7.10) 5 x 1.0.10 6 Wm -2 (respectively 4.1.10) 10 Wm -2 Furthermore, the maximum sound intensity in the acoustic focal region is 1.710. 12 Wm -2 (Corresponding to 3.7 x 4.7.10) 5 x 1.0.10 6 Wm -2 (respectively 1.8.10) 11 Wm -2 For α-alumina).

[0211] Therefore, a minimum sound intensity of 4.7.10 can be achieved within at least a portion of the aforementioned acoustic focal range. 11 Wm -2 (corresponding to 1.6.10) 6 x 1.0.10 6 Wm -2 (4.9.10 respectively) 10 Wm -2 ).

[0212] By heating sample 50 to a minimum temperature of 1375°C (840°C respectively), the sound intensity reached 4.710 in a portion of the acoustic focal region. 11 Wm -2 (4.9.10 respectively) 10 Wm -2 The resulting diamond powder (α-alumina) is densified by sintering.

[0213] Therefore, the first process according to the invention advantageously enables the ceramic powder to be sintered within the acoustic domain. Advantageously, the method allows for precise control of the spatial position that satisfies the sintering conditions of the ceramic powder, thereby achieving the sintering of the ceramic powder.

[0214] In a particular implementation of the first process, the acoustic focal zone moves within the sample when multiple sound waves are emitted.

[0215] Moving the acoustic focal zone within the sample facilitates the sintering of the ceramic powder in different regions of the sample until the desired size and shape of the final sintered ceramic component is obtained.

[0216] In one example, in order to obtain a relative displacement of the acoustic focal region relative to the sample, the sample is moved by a displacement member.

[0217] In another embodiment, in order to obtain a relative displacement of the acoustic focal region relative to the sample, the focusing system is moved by a displacement member.

[0218] In another embodiment, in order to obtain a relative displacement of the acoustic focal region relative to the sample, the acoustic wave generator is simultaneously displaced by a displacement member.

[0219] In a further embodiment, in order to obtain a relative displacement of the acoustic focal region relative to the sample, the acoustic generators are phase-displaced relative to each other by a well-defined value to obtain the displacement of the acoustic focal region in the sample.

[0220] The second process will now be described. As a reminder, the second process is designed to manufacture diamond from a sample containing graphite or amorphous carbon powder.

[0221] As a reminder, amorphous carbon contains a mixture of sp... 2 and sp 3 Atomic bonds, and a possible concentration of hydrogen atoms.

[0222] Advantageously, amorphous carbon, which does not contain hydrogen atoms, typically has an sp2 ratio between 40% and 90%. 3 Mixing rate.

[0223] The second process is advantageously based on the principle of dynamic compression in a first stage, which will be described later, and then on the principle of high-pressure flash sintering in a second stage.

[0224] In the first stage, graphite powder is converted into diamond powder, and then in the second stage, the diamond powder is densified by sintering to form diamond.

[0225] The second process produces uniform dense diamond with improved mechanical strength.

[0226] The second process involves heating the sample 50 to a predetermined temperature.

[0227] The sample is heated to a predetermined minimum temperature. This minimum temperature is preferably higher than the sintering temperature of the diamond powder, which is a function of the pressure applied to the sample.

[0228] As a reminder, for diamond powder, the sintering temperature is 1400°C when a pressure of 5 GPa is applied.

[0229] Preferably, heating is performed by the heating system of the device 100.

[0230] In one embodiment, heating is achieved by using the Joule effect to allow an electric current to flow through multiple cables through the container 70.

[0231] In another embodiment, an induced current is generated in the container 70 by an induction coil, and heating is achieved by using the induction effect.

[0232] Once the sample has reached the predetermined minimum temperature, the second process involves generating and emitting multiple sound waves.

[0233] As can be clearly seen from the description, the step of generating and emitting multiple sound waves is performed after the heating step. The step of generating and emitting multiple sound waves is performed only when the sample 50 is at the predetermined minimum temperature.

[0234] The multiple sound waves are emitted simultaneously over a predetermined duration, preferably over the same duration.

[0235] For example, the duration of each of the multiple sound waves emitted is approximately one hour.

[0236] The plurality of sound waves are preferably generated and emitted by a plurality of sound wave generators 10 controlled by the management unit. The duration of each sound wave emission is controlled by the management unit. Each sound wave generator 10 generates and emits a sound wave of a predetermined power. Preferably, the power generated by each sound wave generator 10 is the same.

[0237] Multiple sound waves together generate a strong sound I at the input of the focusing system 20. e .

[0238] Similar to the first process, the sound intensity I generated at the input of the focusing system e The power injected into the focusing system 20 is determined by the ratio of the power injected into the focusing system 20 to the cross-sectional area of ​​the input end of the focusing system 20. The power injected into the focusing system 20 is determined by multiplying the number of multiple acoustic generators 10 used by the power produced by one acoustic generator 10 (assuming that all acoustic generators produce the same power).

[0239] Then, the emitted sound waves are focused into an acoustic focal region located within the sample 50. The sound waves are emitted along the direction of the focusing system 20, pass through the focusing system, and converge towards the sample 50 into the acoustic focal region.

[0240] Similar to the first process, within the acoustic focal domain, the focused sound wave will produce a sound intensity, which within a certain range corresponds to the sound intensity I at the input of the focusing system. e Multiply by the product factor M of the focusing system. This product factor M is the sound intensity I caused by focusing. e One of the product factors.

[0241] Similar to the first method, the sound intensity in the focal region is non-uniform. More precisely, the spatial distribution of sound intensity on a known focal plane is non-uniform, but rather exhibits the form of an Airy disk. Therefore, on the focal plane, the sound intensity forms a central (circular) point and a series of concentric rings surrounding this central point. The central point concentrates 85% of the sound power. The remaining sound power is distributed in a decreasing manner across the series of concentric rings. The average sound intensity at the central point is 0.85 x M x I. e The sound intensity at 80% of the maximum value at the center point is 2.9 x M x I. e The maximum sound intensity at the center point is 3.7 x M x I. e The maximum sound intensity at the center point is punctual. The spatial distribution of sound intensity on a plane perpendicular to the focal plane is also uneven. The sound intensity gradually decreases as it moves away from the focal plane.

[0242] The acoustic focal region of this invention corresponds to the center point on the focal plane. Therefore, since the maximum intensity within the acoustic focal region is greatest on the focal plane, the maximum sound intensity within the acoustic focal region is 3.7 x M x I. e .

[0243] According to the present invention, for graphite powder, the multiple focused sound waves must be generated together within at least a portion of the acoustic focal domain to produce a value at least equal to 1.10. 12 Wm -2 A sound intensity corresponds to a minimum sound intensity, which is sufficient to achieve a phase change from graphite to diamond.

[0244] According to the present invention, for having a sp 3 An amorphous toner with a mixing ratio between 40% and 90% must be used to focus multiple acoustic waves, which must be generated together within at least a portion of the acoustic focal region to produce a value at least equal to 2.1.10. 12 Wm -2 A sound intensity corresponds to a minimum sound intensity, which is sufficient to achieve a phase change from amorphous carbon to diamond.

[0245] More precisely, for those with a sp 3 An amorphous carbon powder with a mixing ratio of 40% is used to focus the multiple sound waves, which must be generated together within at least a portion of the acoustic focal region, at least equal to 1.4.10. 12 Wm -2 A sound intensity, a strength corresponding to a minimum sound intensity sufficient to achieve a phase change from amorphous carbon to diamond. For a sound with a sp 3 An amorphous carbon powder with a mixing ratio of 90% is used, and the multiple focused sound waves must be generated together within at least a portion of the acoustic focal region, with a value at least equal to 2.1.10. 12 Wm -2 A sound intensity, a strength corresponding to a minimum sound intensity sufficient to achieve a phase change from the amorphous carbon to diamond.

[0246] The following descriptions and values ​​are given using a graphite powder sample as an example. To avoid repetition of the description for an amorphous toner sample, the relevant values ​​for the amorphous toner sample will be given in parentheses.

[0247] In order to obtain 1.10 in at least a portion of the said acoustic focal range 12 Wm -2 (depending on the sp respectively) 3 The blending ratio is between 1.4.10. 12 Wm -2 and 2.1.10 12 Wm -2 The sound intensity between (between) affects the sound intensity I generated at the input of the focusing system. e The product factor M of the focusing system is possible. It may affect multiple parameters in the device, such as the number of acoustic generators, the power generated by these generators, the cross-sectional area of ​​the input of the focusing system, and the product factor M of the focusing system, thereby achieving 1.10 in at least a portion of the acoustic focus domain. 12 Wm -2 A loud sound (depending on the sp) 3 The mixing ratios are between 1.4 and 10. 12 Wm -2 and 2.1.10 12 Wm -2 between).

[0248] As previously stated, the second process according to the invention advantageously converts graphite (amorphous carbon, respectively) into diamond based on the principle of dynamic compression.

[0249] In order to achieve a phase transformation from graphite (amorphous carbon) to diamond through dynamic compression, those skilled in the art know that two conditions must be met: Under sufficient pressure, diamond is more stable than graphite (which is amorphous carbon, respectively). Give carbon atoms enough kinetic energy to break the metastable state of graphite (which is amorphous carbon) caused by the double bonds between carbon atoms.

[0250] In other words, applying sufficient pressure to graphite (which is amorphous carbon) will stabilize diamond, and sufficient kinetic energy will cause a phase change.

[0251] For dynamic compression using shock waves, as described in the prior art, pressure and kinetic energy are provided by the shock. For a shock wave, pressure and kinetic energy can be expressed as functions of the shock intensity. Therefore, the shock intensity must be sufficient to ensure that: The pressure reached exceeds a sufficiently minimum pressure that makes diamond more stable than graphite (which is amorphous carbon, respectively), for example, at least 5 GPa; 5 GPa corresponds to the stable pressure of diamond under static compression; During the duration of the shock wave emission, the kinetic energy of the atoms is sufficient to disrupt the metastable state of the graphite (specifically, the amorphous carbon).

[0252] For example, Erskine et al. showed in their publication that, for dynamic compression using shock waves, a graphite sample was transformed into diamond in a few hundred nanoseconds at 6 GPa and in less than 10 nanoseconds at 20 GPa.

[0253] Similarly, for the use of sound wave compression, pressure and kinetic energy can be expressed as functions of sound intensity.

[0254] The sound intensity must be sufficient to ensure: The pressure reached exceeded a sufficiently low minimum pressure, making diamond more stable than graphite (which is amorphous carbon). During the duration of the sound wave emission, the kinetic energy of the atoms is sufficient to disrupt the metastable state of the graphite (specifically, the amorphous carbon).

[0255] For a given material initially subjected to ambient temperature and pressure, each acoustic intensity value gives a unique pair of values ​​(pressure, kinetic energy). These acoustic intensity values ​​have been characterized in great detail through the so-called Hugoniot curve study, which is included in the book "LASL shock Hugoniot data" published by the University of California Press in 1980.

[0256] The effect of kinetic energy on the transformation of graphite (amorphous carbon) into diamond can be modeled using a kinetic Arrhenius law, similar to the effect of temperature. This model explains the role of kinetic energy in dynamic compression, replacing the heat energy in static compression, thus causing graphite (amorphous carbon) to transform into diamond. For example, for graphite (amorphous carbon) with a kinetic energy of 1 / 2000 ppm, the effect of kinetic energy on the transformation of graphite (amorphous carbon) into diamond can be modeled using a kinetic Arrhenius law. 3 Dynamic compression was performed on amorphous carbon (with a mixture ratio of 40% to 90%), with a sound intensity of approximately 2.10. 13 Wm -2 (2.7.10 respectively) 13 Wm -2 (For those with a sp) 3 (40% amorphous toner) to 4.0.10 13 Wm -2 (For those with a sp) 3 (90% amorphous toner) triggers a pressure of 25 GPa (from 34 GPa for a single sp) 3 (40% amorphous toner) up to 49 GPa (for a sample with a sp...) 3 (90% amorphous toner) and 0.16 eV of kinetic energy, equivalent to thermal kinetic energy caused by a temperature of about 1500°C.

[0257] Figure 7 A modeling curve is displayed, plotting graphite powder (solid line curve) with 40% sp. 3 The blended amorphous toner (dashed curve) and has 90% sp 3 The induced pressure of the mixed amorphous carbon powder (dotted curve) is used as a function of sound intensity.

[0258] Figure 8 A modeling curve is displayed, plotting graphite powder (continuous line) with 40% sp. 3 The mixed amorphous toner (dashed line) and has 90% sp 3 The kinetic energy of the mixed amorphous carbon powder (dots and lines) is a function of the sound intensity. When the sound intensity is sufficient, the duration of the sound emission then determines the proportion of the phase change, i.e., the percentage of graphite (amorphous carbon) converted into diamond. In other words, for a given sound intensity, the percentage of graphite (amorphous carbon) converted into diamond is a function of the duration of the sound emission at that intensity. More precisely, the longer the duration of the sound intensity, the greater the percentage of graphite (amorphous carbon) converted into diamond. Furthermore, for a given percentage of graphite (amorphous carbon) converted into diamond, the greater the emitted sound intensity, the shorter the duration of the sound emission.

[0259] Based on Arrhenius's law, the reaction rate k can be approximated by the following relationship:

[0260] in E a It is the activation energy for the transformation of graphite into diamond, that is, the energy required for carbon atoms to break the metastable state of graphite, and A is a constant that depends primarily on the mechanism involved in the phase transformation (thermal diffusion, martensitic transformation).

[0261] E a It is approximately 0.2 eV, according to Xie et al., Journal of the American Chemical Society, 139, 7, pages 2545-2548, published in 2017.

[0262] Based on previous experimental results by Erskine et al., the constant A is approximately 2.310. 9 s -1 .

[0263] Therefore, for a graphite powder (each having a sp...) 3 Dynamic compression of amorphous toner with a blending ratio between 40% and 90%, with a sound intensity of approximately 1.1.10. 12 Wm -2 The magnitude (respectively 1.4.10) 12 Wm -2 (For those with a sp) 3 (Amorphous toner with a blending rate of 40%) to 2.1.10 12 Wm -2 (For those with 90% sp) 3 The amorphous carbon powder (mixed) can achieve a pressure on the order of 5 GPa (corresponding to the stable pressure of diamond) (from 6.5 GPa (for a diamond with 40% sp...). 3 (mixed amorphous carbon powder) up to 9.5 GPa (for a powder with a sp) 3 (90% amorphous toner) and a kinetic energy on the order of 0.012 eV (for a substance with a sp...) 3 (Amorphous carbon with a mixture rate between 40% and 90%). The rate of one-phase change k caused by this kinetic energy is approximately 410 s. -1 (with a sp) 3 The values ​​for amorphous carbon with a blending rate between 40% and 90% are the same.

[0264] Percentage phase change is expressed as

[0265] Where t is time.

[0266] This means 95% conversion within 3 / k seconds and 99% conversion within 5 / k seconds. Therefore, 99% conversion of the region under dynamic compression is achieved in approximately 0.01 seconds (compared to a region with a sp...). 3 It is possible to have the same value for amorphous carbon with a blending rate between 40% and 90%.

[0267] For example, Figure 9 A graph is shown plotting the time required to emit a sound wave as a function of the sound wave intensity, to reproduce a diamond-graphite sample (solid line curve) with a sp in diamond. 3 An amorphous carbon sample with a mixing ratio of around 40% (dashed curve) and a sample with a sp in diamond. 3 Conditions for a 99% phase change in an amorphous carbon sample (dotted curve) with a mixing ratio between 40%.

[0268] like Figure 9 As shown, for a single graphite powder, the magnitude of a sound intensity is on the order of 1.4.10. 13 Wm -2 At this pressure, a pressure of 20 GPa can be reached, which is higher than the minimum pressure required to stabilize diamond. This imparts kinetic energy to carbon atoms, allowing at least 99% of the graphite sample to transform into diamond within a time frame on the order of 10 ns. The intensity of the sound is on the order of 1.610. 12 Wm -2 A pressure of up to 6 GPa can be achieved, which is higher than the minimum pressure required to stabilize diamond, imparting a kinetic energy of 0.017 eV to carbon atoms, allowing at least 99% of graphite samples to transform into diamond within a timeframe on the order of 1 ms. On the other hand, if the pressure is still sufficient to maintain the stability of diamond, then pressures below 5.10... 11 Wm -2 A loud noise will trigger a phase change that lasts for more than one hundred hours.

[0269] Returning to the second process according to the invention, the multiple focused sound waves will thus generate a sound intensity with induced sound pressure and kinetic energy in the acoustic focal region, as described above.

[0270] In order to cause graphite (each having a sp) to occur in the acoustic focal region 3 When amorphous carbon (with a mixture ratio between 40% and 90%) undergoes a phase transformation into diamond, the resulting sound intensity must be at least equal to a minimum sufficient sound intensity, i.e., 1.10, within at least a portion of the acoustic focal range. 12 Wm -2 (from 1.4.10 respectively)12 Wm -2 (For those with a sp) 3 (Amorphous toner with a blending rate of 40%) to 2.1.10 12 Wm -2 (For those with a sp) 3 (Amorphous toner with a blending rate of 90%).

[0271] As previously stated, when the acoustic intensity obtained in the acoustic focal region is sufficient to achieve a phase change from graphite (amorphous carbon, respectively) to diamond, the emission duration of the acoustic intensity will affect the proportion of the phase change from graphite (amorphous carbon, respectively) to diamond within the acoustic focal region. In other words, for a given acoustic intensity within the acoustic focal region, the percentage of graphite (amorphous carbon, respectively) to diamond conversion within the acoustic focal region is a function of the duration of acoustic wave emission. More precisely, for a given acoustic intensity, the percentage of graphite (amorphous carbon, respectively) to diamond conversion increases with increasing acoustic wave emission duration.

[0272] In the second stage of the process, once the graphite (or amorphous carbon) is converted into diamond powder or very low-density diamond, the conditions for sintering to densify the diamond are advantageously met by combining pressure and the heating temperature of sample 50.

[0273] According to the second process of the present invention, from 1.10 12 Wm -2 A loud sound (from 1.4.10 respectively) 12 Wm -2 (For those with a sp) 3 (Amorphous toner with a blending rate of 40%) to 2.1.10 12 Wm -2 (For those with sp) 3 (Starting with 90% amorphous toner), and a minimum heating temperature of 1300°C (from 1250°C for those with sp) 3 Mix to 40% amorphous toner) and heat to 1100°C (for products with SP). 3 (Mixed into 90% amorphous carbon powder), by using graphite (each having a sp...) 3 The amorphous carbon (with a mixture ratio of 40% to 90%) is transformed into diamond and sintered from graphite powder (each having a sp... 3 Diamond is obtained by mixing amorphous carbon with a mixture rate of 40% to 90%.

[0274] To prevent diamond from graphitizing, the minimum heating temperature must not exceed 1700°C in an inert gas atmosphere or under vacuum.

[0275] Example 2: A simulation was performed to replicate 100 devices on a small scale and determine a desired volume of the acoustic focal region.

[0276] In this simulation, the focusing system 20 is a plano-concave spherical lens. The dimensions of the plano-concave spherical lens are as follows: the diameter of the first surface 21 is 7.5 mm, its center thickness is 2 mm, and the radius of curvature of the second surface 22 is 4 mm. The plano-concave spherical lens is made of aluminum.

[0277] 190 piezoelectric actuators, each with a diameter of 0.5 mm, are evenly distributed opposite the first surface 21 of the plano-concave spherical lens. The 190 piezoelectric actuators are bonded to the first surface 21 of the plano-concave spherical lens. Each piezoelectric actuator emits a sound wave with a frequency of 20 MHz. Each piezoelectric actuator generates a power of 1 W.

[0278] The following values ​​correspond to a sample of graphite powder. For ease of comparison, the values ​​given in parentheses correspond to a sample of amorphous carbon powder with a concentration between 40% and 90%. 3 Mixing rate.

[0279] The simulation yields a acoustic focal region whose volume can be approximated as an ellipsoid with a circular cross-section and a semi-major axis of 0.5 mm (from 0.66 mm for a given sp). 3 (40% amorphous toner) to 0.87 (for a mixture with a sp. 3 (90% amorphous toner), and half of the short axis is 0.18 mm (from 0.24 mm respectively for a sp 3 (40% amorphous toner) to 0.32 mm (for a powder with a sp...) 3 (Amorphous toner with a blending rate of 90%).

[0280] Through this simulation, we can derive the product factor M of the plano-concave spherical lens. In this case, the product factor M is the ratio of the entry cross-section of the plano-concave spherical lens to the cross-section of the acoustic focal region on the focal plane. Therefore, the product factor M is 4.3.10. 2 (from 2.4.10 respectively) 2 (For those with a sp) 3 (Amorphous toner with a blending rate of 40%) to 1.3.10 2 (For those with a sp) 3 (Amorphous toner with a blending rate of 90%).

[0281] As is well known, as long as the angular aperture of the plano-concave spherical lens remains constant, increasing its size will not affect the size of the acoustic focal region. As a reminder, the angular aperture is proportional to the ratio of the diameter of the first surface of the plano-concave spherical lens to the radius of curvature of the second surface.

[0282] Therefore, a plano-concave spherical lens, having a first surface with a diameter of 450 mm and a second surface with a radius of curvature of 240 mm, can maintain the acoustic focal domain dimensions obtained in the simulation. It is well known that lens thickness has no effect on the angular aperture. The lens thickness is set to 1 cm to minimize the propagation distance of the sound waves while maintaining lens strength.

[0283] At this size, the product factor M of the plano-concave spherical lens is 1.6.10. 6 (from 8, 9, and 10 respectively) 5 (For those with a sp) 3 (40% amorphous toner) to 4.7.10 5 (For those with a sp) 3 (Amorphous toner with a blending rate of 90%).

[0284] To cover the first surface of this plano-concave spherical lens, we can use, for example, 1600 piezoelectric actuators with a diameter of 10 mm, or 10000 piezoelectric actuators with a diameter of 4 mm, or 100 piezoelectric actuators with a diameter of 40 mm.

[0285] If we choose 1600 piezoelectric actuators with a diameter of 10 mm as an example, and each actuator generates a sound wave with a power of 100 W (200 W respectively), then multiple sound waves will together generate 1.0.10 at the input end of the lens. 6 Wm -2 (2.0.10 respectively) 6 Wm -2 A loud I e .

[0286] It should be noted that sound intensity I e This corresponds to the ratio of the power injected into the plano-concave spherical lens to the cross-sectional area of ​​the first surface of the plano-concave spherical lens. The power injected into the lens corresponds to the number of piezoelectric actuators used multiplied by the power generated by each piezoelectric actuator.

[0287] It is worth noting that the same sound intensity can be obtained at the entrance of the plano-concave spherical lens whether using 10,000 piezoelectric actuators (4 mm in diameter) each generating 15.90 W of power, or 100 piezoelectric actuators (40 mm in diameter) each generating 1590 W of power.

[0288] In a configuration with 1600 piezoelectric actuators, this yields an average sound intensity of 1.310 in the focal plane of the acoustic focal domain. 12 Wm -2 (0.85 x 1.6.10) 6 x 1.0.10 6 Wm -2 (respectively 1.5.10) 12 Wm -2 (For those with 40% sp) 3 (Amorphous toner powder mixed with other materials) up to 0.8.10 12 (For those with 90% sp) 3 (The mixed amorphous carbon powder), and the maximum sound intensity in the acoustic focal region is 5.4.10. (12) Wm -2 (3.7 x 1.6.10 6 x 1.0.10 6 Wm -2 (6.6.10 respectively) 12 Wm -2 (For those with 40% sp) 3 (Mixed amorphous toner) up to 3.6.10 12 (For those with 90% sp) 3 Hybridized amorphous toner).

[0289] Therefore, within a portion of the aforementioned acoustic focal range, a value greater than 10 can be achieved. 12 Wm -2 The sound intensity (respectively 1.4.10) 12 Wm -2 (For those with sp) 3 (Amorphous toner with a blending rate of 40%) to 2.1.10 12 (Regarding sp) 3 (90% amorphous carbon powder), sufficient to separate from graphite powder (sp respectively) 3 A strong sound is produced by manufacturing diamond powder using a mixture of amorphous carbon powder with a blending rate between 40% and 90%.

[0290] Sample 50 was heated in parallel at a minimum temperature of 1300°C (from 1250°C for samples with sp...). 3 (40% amorphous toner) to 1100°C (for those with sp) 3 (Amorphous carbon powder with a mixing ratio of 90%), wherein the sound intensity reaches 1.10 in a portion of the acoustic focal region. 12 Wm -2 (from 1.4.10 respectively) 12Wm -2 (Regarding sp) 3 (40% amorphous toner) to 2.1.10 12 (Regarding sp) 3 Amorphous carbon powder with a mixing rate of 90% is used to densify the resulting diamond powder through sintering.

[0291] Therefore, the second process according to the invention can advantageously create a diamond seed within the acoustic focal region, or expand a seed that is previously present in the sample.

[0292] Advantageously, the second process allows for precise control of the spatial position that satisfies the conditions for diamond formation. Unlike shock wave technology, the second process according to the invention also advantageously enables the production of diamonds without damaging the sample.

[0293] The second process according to the invention can also control the duration of sound wave emission.

[0294] In a particular implementation of the second process, the acoustic focal zone moves within the sample during sound wave emission.

[0295] This special mode of the second process is achieved when the time required to emit multiple sound waves is longer than the time required to convert a desired predefined percentage of graphite (amorphous carbon, respectively) in the acoustic focal region into diamond.

[0296] By moving the acoustic focal region within the sample, a diamond seed can be grown to the desired diamond size and shape. The direction of movement of the acoustic focal region within the sample guides the direction of diamond growth to achieve the desired shape.

[0297] The velocity of the acoustic focal region in the sample is advantageously correlated with the duration of acoustic emission required to convert a desired predefined percentage of graphite (a few amorphous carbons) in the acoustic focal region into diamond. Therefore, the velocity of the acoustic focal region in the sample is a function of the acoustic intensity of the sound waves in the acoustic focal region, since the acoustic intensity determines the emission duration required to convert the desired predefined percentage of graphite (a few amorphous carbons) into diamond.

[0298] Preferably, since the emission time required to convert all or part of graphite (or amorphous carbon) into diamond is very short, typically less than one second, the acoustic focal zone can be moved continuously by adjusting the speed at which the acoustic focal zone is moved.

[0299] In one embodiment, in order to obtain a relative displacement of the acoustic focal region relative to the sample, the sample is moved by a displacement member.

[0300] In another embodiment, in order to obtain a relative displacement of the acoustic focal region relative to the sample, the focusing system is moved by a displacement member.

[0301] In another embodiment, in order to obtain a relative displacement of the acoustic focal region relative to the sample, the acoustic generator is simultaneously displaced by a displacement member.

[0302] In a further embodiment, in order to obtain a relative displacement of the acoustic focal region relative to the sample, the acoustic generators are phase-displaced relative to each other by a well-defined value to obtain the displacement of the acoustic focal region in the sample.

[0303] The above description clearly demonstrates that the present invention achieves its intended objectives through its various features and advantages. Specifically, the present invention provides two methods for manufacturing diamonds, which have the advantage of not damaging the sample and allowing for precise control over the direction of diamond growth.

Claims

1. A method for manufacturing a ceramic component from a sample (50) of ceramic powder, characterized in that: The method includes the following steps: The ceramic powder sample (50) is heated to a predetermined minimum heating temperature using a heating system, and then... Multiple sound waves are generated and emitted toward a focusing system (20) by multiple sound wave generators, each configured to emit a sound wave with a frequency f between 1 MHz and 100 MHz. The multiple sound waves together generate a sound intensity at the input of the focusing system. , The focusing system (20) focuses the plurality of acoustic waves into a single acoustic focal region within the ceramic powder sample (50), wherein the focusing system defines a product factor M. The focused plurality of sound waves together generate a minimum sound intensity at at least a portion of the acoustic focal region, the minimum sound intensity being at least M x I. e The minimum heating temperature applied to the sample (50) of the ceramic powder, combined with the minimum heating temperature, is sufficient to sinter the ceramic powder in the portion of the acoustic domain.

2. The method according to claim 1, characterized in that: The minimum heating temperature of the ceramic powder sample (50) is higher than a sintering temperature of the ceramic powder.

3. The method according to any one of the preceding claims, characterized in that: The ceramic powder is selected from: diamond powder, tungsten carbide powder, silicon nitride powder, fully stabilized zirconium oxide powder, α-alumina powder, γ-alumina powder, and titanium dioxide powder.

4. The method according to any one of the preceding claims, characterized in that: The method includes shifting the acoustic focal region in the sample (50) during the emission of the plurality of acoustic waves.

5. An apparatus (100) for performing the method according to any one of the preceding claims, characterized in that: The device includes: A system for heating the sample (50), Multiple sound wave generators (10), each configured to generate a sound wave with a frequency f between 1 MHz and 100 MHz, The plurality of acoustic wave generators (10) and the heating system of the sample (50) are independent components within the device (100). A focusing system (20) is used for the plurality of acoustic waves in a sonic domain within the sample (50), the focusing system defining the product factor M.

6. The apparatus (100) according to claim 4, characterized in that: Each acoustic wave generator (10) is a piezoelectric actuator.

7. The apparatus (100) according to claim 4 or 5, characterized in that: The device also includes a component for shifting the acoustic focal region within the sample (50).

8. The apparatus (100) according to the preceding claim, characterized in that: The component for moving the acoustic focal region in the sample (50) is a component for moving the acoustic focusing system and / or a component for moving the sample and / or a component for moving the acoustic generator and / or a component for changing the phase of the acoustic generator.

9. A method for manufacturing diamond from a sample (50), said sample (50) comprising graphite powder, characterized in that: The method includes the following steps: The graphite powder sample (50) is heated to a predetermined minimum temperature using a heating system, and then... Multiple sound waves are generated and emitted to a focusing system (20) by multiple sound wave generators, each sound wave generator being configured to emit a sound wave with a frequency f between 1 MHz and 100 MHz, the multiple sound waves together generating a sound intensity at the input of the focusing system. , The focusing system (20) focuses the plurality of acoustic waves into a single acoustic focal region within the graphite powder sample (50), wherein the focusing system defines a product factor M. The focused plurality of sound waves together generate a sound intensity at least equal to M x I in at least a portion of the acoustic focal region. e = 1.10 12 Wm -2 This corresponds to a minimum sound intensity, and is sufficient to: In the first stage, a phase change from graphite powder to diamond powder is achieved, then... In a second stage, the diamond powder obtained is sintered in conjunction with the minimum heating temperature applied to the sample (50).

10. The method according to claim 9, characterized in that: The minimum heating temperature of the sample (50) containing graphite powder is higher than a sintering temperature of the graphite powder.

11. A method for manufacturing diamond from a sample (50), said sample (50) comprising amorphous carbon powder, characterized in that: The method includes the following steps: The sample (50) of amorphous carbon powder is heated to a predetermined minimum temperature using a heating system, and then... Multiple sound waves are generated and emitted toward a focusing system (20) by multiple sound wave generators, each sound wave generator being configured to emit a sound wave with a frequency f between 1 MHz and 100 MHz, the multiple sound waves together generating a sound intensity at the input of the focusing system. , The focusing system (20) focuses the plurality of acoustic waves within an acoustic focal domain of the amorphous toner sample (50), wherein the focusing system defines a product factor M. The focused plurality of sound waves together generate a sound intensity at least equal to M x I in at least a portion of the acoustic focal region. e = 2.1.10 12 W . m -2 This corresponds to a minimum sound intensity, and is sufficient to: In the first stage, a phase change from amorphous carbon powder to diamond powder is achieved, then... In a second stage, the diamond powder obtained is sintered in conjunction with the minimum heating temperature applied to the sample (50).

12. The method according to claim 11, characterized in that: The minimum heating temperature of the sample (50) containing amorphous carbon powder is higher than a sintering temperature of the amorphous carbon powder.

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