A method for preparing copper-modified lead apatite

Abstract

This invention relates to a method for preparing copper-modified lead apatite. The method includes: sequentially subjecting precursor materials to a first hydrothermal process and a second hydrothermal process, followed by calcination to obtain copper-modified lead apatite; the precursor materials include liquid-phase precursor materials or solid-phase precursor materials; the liquid-phase precursor material is obtained by mixing lead salt, copper salt, phosphorus source, pH adjuster, chelating agent, and solvent; the solid-phase precursor material is obtained by mixing copper compound and lead compound; the temperature of the first hydrothermal process is lower than the temperature of the second hydrothermal process. The preparation method provided by this invention, by treating rationally designed raw materials using a specific hydrothermal process, can obtain copper-modified lead apatite with extremely low impurity content, which is beneficial for broadening the application fields of copper-modified lead apatite and improving its performance.

Description

Technical Field

[0001] This invention relates to the field of materials synthesis, specifically to a method for preparing copper-modified lead apatite. Background Technology

[0002] Currently, existing technologies propose a copper-modified lead apatite material, indicating that this material may possess diamagnetic and superconducting properties, with the molecular formula Pb. 10-x Cu x (PO4)6O has a lead apatite structure.

[0003] However, the existing technology discloses a synthesis process that involves three steps of calcination using lead sulfate, lead oxide, pure copper, and pure phosphorus. This method is costly, difficult to control, and contains Cu2S impurities, which makes it difficult for the copper-modified lead apatite material to perform well in practical applications. Summary of the Invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for preparing copper-modified lead apatite, so as to solve the problem that the product obtained in the existing preparation process has impurities and low purity.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] This invention provides a method for preparing copper-modified lead apatite, the method comprising:

[0007] The precursor material was subjected to first and second hydrothermal treatments in sequence, followed by calcination to obtain copper-modified lead apatite.

[0008] The precursor material includes liquid-phase precursor material or solid-phase precursor material;

[0009] The liquid-phase precursor material is obtained by mixing lead salt, copper salt, phosphorus source, pH adjuster, chelating agent and solvent;

[0010] The solid-phase precursor material includes a mixture of copper and lead compounds;

[0011] The temperature of the first hydrothermal treatment is less than the temperature of the second hydrothermal treatment.

[0012] The preparation method provided by this invention, by treating the rationally designed raw materials through a specific hydrothermal process, can obtain copper-modified lead apatite with extremely low impurity content, which is beneficial to broadening the application field of copper-modified lead apatite and improving its performance.

[0013] As a preferred embodiment of the present invention, the preparation process of the liquid-phase precursor material is as follows:

[0014] Lead salt, lead salt, chelating agent and solvent were prepared into a solution, and then the pH value was adjusted with a pH adjuster. Then a phosphorus source was added to obtain the liquid phase precursor material.

[0015] As a preferred embodiment of the present invention, the total concentration of copper and lead elements in the prepared solution is 0.1-0.15 mol / L;

[0016] Preferably, the amount of the chelating agent added is 1-1.1 times the total concentration of copper and lead in the solution;

[0017] Preferably, the final pH value for pH adjustment is 8-12;

[0018] Preferably, the molar ratio of (Cu+Pb) / P in the liquid-phase precursor is (1.5-1.7):1;

[0019] Preferably, the pH value of the liquid phase precursor is 8-12.

[0020] As a preferred embodiment of the present invention, the preparation process of the solid-phase precursor material is as follows:

[0021] S1. Lead oxide, lead salt, and copper oxide are mixed and ball-milled to obtain the first material, which is then mixed with copper salt to obtain the solid-phase precursor material.

[0022] Alternatively, S2, mix oxides, lead salts and copper salts to obtain solid-phase precursor materials.

[0023] As a preferred technical solution of the present invention, the molar ratio of lead oxide, lead salt, copper oxide and copper salt in S1 is (1-3):(0-1):(2-19 / 3):(1-8 / 3);

[0024] Preferably, the molar ratio of Pb to Cu in the solid precursor obtained in S1 is (7-9):(1-3).

[0025] As a preferred technical solution of the present invention, the molar ratio of (Cu+Pb) / P in the solid precursor material obtained in S2 is 5 / 3, wherein the molar ratio of Pb / Cu is (7-10):(0-3).

[0026] As a preferred technical solution of the present invention, when the precursor material is a solid-phase precursor material, the solid-phase precursor material is mixed with a solvent before the first hydrothermal treatment to obtain a mixture before the first hydrothermal treatment is performed.

[0027] Preferably, the solid-liquid ratio of the solid precursor and the solvent is 1:(40-60) g / mL;

[0028] Preferably, the pH value of the mixture is 8-12.

[0029] As a preferred embodiment of the present invention, the temperature of the first hydrothermal element is 60-80℃;

[0030] Preferably, the first hydrothermal time is 3-6 hours.

[0031] As a preferred embodiment of the present invention, the temperature of the second hydrothermal element is 150-180℃;

[0032] Preferably, the second hydrothermal time is 6-24 hours.

[0033] As a preferred embodiment of the present invention, the calcination temperature is 500-925℃;

[0034] Preferably, the roasting time is 10-24 hours.

[0035] Compared with existing technical solutions, the present invention has the following beneficial effects:

[0036] (1) The copper-modified lead apatite obtained by the preparation method provided by the present invention has a controllable doping ratio, high purity, and no oxide or phosphate impurities.

[0037] (2) Copper doping is stable, and lead and copper can be completely integrated into the apatite structure.

[0038] (3) Compared with the direct mixing of oxides and phosphates, this method effectively avoids the problem of high-temperature lead oxide volatilization and prevents stoichiometric imbalance caused by PbO volatilization. Attached Figure Description

[0039] Figure 1 This is a flowchart of the preparation method of copper-modified lead apatite provided in the embodiments of the present invention;

[0040] Figure 2 This is the XRD pattern of the copper-modified lead apatite product obtained in Example 1 of this invention;

[0041] Figure 3 This is a ZFC-FC result diagram of the copper-modified lead apatite product obtained in Example 1 of this invention;

[0042] Figure 4 This is a hysteresis loop result diagram of the copper-modified lead apatite product obtained in Example 1 of the present invention;

[0043] Figure 5 This is the XRD pattern of the copper-modified lead apatite product obtained in Example 2 of this invention;

[0044] Figure 6 This is a ZFC-FC result diagram of the copper-modified lead apatite product obtained in Example 2 of the present invention;

[0045] Figure 7This is a hysteresis loop result diagram of the copper-modified lead apatite product obtained in Example 2 of the present invention;

[0046] Figure 8 This is a diagram showing the hysteresis loop of the copper-modified lead apatite product obtained in Example 2 of this invention after removing the paramagnetic backplane.

[0047] Figure 9 This is the EPR spectrum of the copper-modified lead apatite product obtained in Example 2 of this invention at 25°C.

[0048] Figure 10 This is the XRD pattern of the copper-modified lead apatite product obtained in Example 3 of this invention;

[0049] Figure 11 This is a ZFC-FC result diagram of the copper-modified lead apatite product obtained in Example 3 of the present invention;

[0050] Figure 12 This is a graph showing the hysteresis loop (300K) of the copper-modified lead apatite product obtained in Example 3 of this invention.

[0051] Figure 13 This is a hysteresis loop (300K) diagram of the copper-modified lead apatite product obtained in Example 3 of the present invention after removing the diamagnetic straight line;

[0052] Figure 14 This is a graph showing the hysteresis loop (10K) of the copper-modified lead apatite product obtained in Example 3 of this invention after removing the paramagnetic straight line;

[0053] Figure 15 These are comparison images of the XRD patterns of the products obtained in Embodiments 1, 2, and 3 of this invention;

[0054] Figure 16 This is the XRD pattern of the copper-modified lead apatite product obtained in Example 4 of this invention;

[0055] Figure 17 This is a ZFC-FC result diagram of the copper-modified lead apatite product obtained in Example 4 of the present invention;

[0056] Figure 18 This is a graph showing the hysteresis loop (300K) of the copper-modified lead apatite product obtained in Example 4 of this invention.

[0057] Figure 19 These are comparison images of the XRD patterns of the products obtained in Embodiments 1 and 4 of this invention;

[0058] Figure 20 This is a comparison diagram of the hysteresis loop (300K) of the products obtained in Embodiments 1 and 4 of this invention;

[0059] Figure 21This is the XRD pattern of the copper-modified lead apatite product obtained in Example 5 of this invention;

[0060] Figure 22 This is a graph showing the hysteresis loop (300K) of the copper-modified lead apatite product obtained in Example 5 of this invention.

[0061] Figure 23 This is a graph showing the hysteresis loop (300K, -0.2T to 0.2T) of the copper-modified lead apatite product obtained in Example 5 of this invention.

[0062] Figure 24 This is a sample test connection diagram of the copper-modified lead apatite product obtained in Example 5 of the present invention when the resistance is measured by the four-electrode method.

[0063] Figure 25 This is the RT curve of channel 1 of the copper-modified lead apatite product obtained in Example 5 of the present invention;

[0064] Figure 26 This is the RT curve of the copper-modified lead apatite product obtained in Example 5 of this invention after removing the Pb metal backing from channel 1;

[0065] Figure 27 This is the RT curve of channel 2 of the copper-modified lead apatite product obtained in Example 5 of the present invention;

[0066] Figure 28 This is a supplementary 1R-T curve of the copper-modified lead apatite product obtained in Example 5 of the present invention;

[0067] Figure 29 This is a supplementary 2R-T curve for the copper-modified lead apatite product obtained in Example 5 of this invention;

[0068] Figure 30 This is a supplementary 3R-T curve for the copper-modified lead apatite product obtained in Example 5 of this invention;

[0069] Figure 31 This is a supplementary 4R-T curve for the copper-modified lead apatite product obtained in Example 5 of this invention;

[0070] Figure 32 This is the refined XRD pattern of the dried sample obtained in step (8) of Example 3 of the present invention;

[0071] Figure 33 This is a refined XRD pattern of the copper-modified lead apatite product obtained in Example 3 of this invention.

[0072] Figure 34 This is a schematic diagram of the structure of the copper-modified lead apatite product obtained in Example 3 of the present invention;

[0073] Figure 35This is a finely refined XRD pattern of the copper-modified lead apatite product obtained in Example 1 of this invention;

[0074] Figure 36 This is a finely detailed XRD pattern of the copper-modified lead apatite product obtained in Example 4 of this invention.

[0075] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims. Detailed Implementation

[0076] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0077] This embodiment provides a method for preparing copper-modified lead apatite, such as... Figure 1 As shown, the preparation method includes:

[0078] The precursor material was subjected to first and second hydrothermal treatments in sequence, followed by calcination to obtain copper-modified lead apatite.

[0079] The precursor material includes liquid-phase precursor material or solid-phase precursor material;

[0080] The liquid-phase precursor material is obtained by mixing lead salt, copper salt, phosphorus source, pH adjuster, chelating agent and solvent;

[0081] The solid-phase precursor material includes a mixture of copper and lead compounds;

[0082] The temperature of the first hydrothermal treatment is less than the temperature of the second hydrothermal treatment.

[0083] The copper compounds include copper oxides and copper hydroxides, and lead oxides and lead hydroxides.

[0084] In this invention, the chemical formula of the copper hydroxide-modified lead apatite obtained after hydrothermal treatment is Pb. 10-x Cu x (PO4)6(OH)2.

[0085] In this invention, the lead salt includes organic acid salts and / or inorganic acid salts. Specifically, inorganic acid salts can be lead sulfate, lead chloride, lead carbonate, lead nitrate, etc.; organic acid salts can be lead acetate, etc.

[0086] In this invention, the copper salt includes organic copper salts and / or inorganic copper salts. Inorganic copper salts include copper sulfate, copper nitrate, copper chloride, copper phosphate, etc.; organic copper salts may be selected from copper acetate, etc.

[0087] In this invention, the phosphorus source includes phosphoric acid and / or phosphates, such as sodium phosphate, sodium monohydrogen phosphate, sodium dihydrogen phosphate, potassium phosphate, potassium monohydrogen phosphate, potassium dihydrogen phosphate, etc.

[0088] In this invention, the pH adjuster includes inorganic bases such as sodium hydroxide and potassium hydroxide, or organic bases such as triethylamine.

[0089] In this invention, the chelating agent includes aminocarboxylate, aminocarboxylic acid, hydroxycarboxylic acid, hydroxycarboxylate, or organophosphonate, etc.

[0090] In this invention, the chelating agent may specifically be selected from ethylenediaminetetraacetic acid, diethylenetriaminepentacarboxylic acid, aminotriacetic acid, sodium aminotriacetate, sodium aminotriacetate, diethylenetriaminepentacarboxylic acid salt, tartaric acid, sodium alginate, sodium ethylenediaminetetramethylene phosphate, or diethylenetriaminepentamethylene phosphonate, etc.

[0091] In this invention, the solvent includes water or ethanol, which are solvents for the corresponding metal compounds of this invention.

[0092] In this invention, the copper oxide includes copper oxide, and the copper hydroxide includes copper hydroxide, basic copper carbonate, etc.

[0093] In this invention, the lead oxide includes lead oxide, and the lead hydroxide includes lead hydroxide, etc.

[0094] In this invention, when various raw materials are used in a corresponding manner, the following ratio limits must be met. For example, when using copper phosphate or lead phosphate as the phosphorus source in the liquid phase precursor, it is necessary to ensure that the amount of lead element is consistent with the elemental composition of the prepared product. That is, under the premise of meeting the ratio, some of the aforementioned raw materials may not be added, i.e., the amount added is 0.

[0095] Specifically, the preparation process of the liquid-phase precursor material is as follows:

[0096] Lead salt, lead salt, chelating agent and solvent were prepared into a solution, and then the pH value was adjusted with a pH adjuster. Then a phosphorus source was added to obtain the liquid phase precursor material.

[0097] The total concentration of copper and lead in the prepared solution is 0.1-0.15 mol / L, for example, it can be 0.1 mol / L, 0.11 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L or 0.15 mol / L, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0098] The amount of chelating agent added is 1-1.1 times the total concentration of copper and lead in the solution, for example, it can be 1, 1.02, 1.04, 1.06, 1.08 or 1.1 times, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0099] The endpoint pH value for pH adjustment is 8-12, such as 8, 8.5, 9, 9.5, 10, 10.2, 10.4, 10.6, 10.8, 11, 11.5 or 12, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0100] Stirring is performed during the pH adjustment process;

[0101] The stirring speed in the pH adjustment is 50-500 r / min, for example, it can be 50 r / min, 100 r / min, 200 r / min, 300 r / min, 400 r / min or 500 r / min, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0102] The stirring time during pH adjustment is 30-45 minutes, for example, it can be 30 minutes, 35 minutes, 40 minutes or 45 minutes, but it is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0103] The molar ratio of (Cu+Pb) / P in the liquid-phase precursor material is (1.5-1.7):1, for example, it can be 1.5:1, 1.52:1, 1.54:1, 1.56:1, 1.58:1, 1.6:1, 1.62:1, 1.64:1, 1.66:1, 1.68:1 or 1.7:1, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0104] The pH value of the liquid phase precursor material is 8-12, for example, it can be 8, 8.5, 9, 9.5, 10, 10.2, 10.4, 10.6, 10.8, 11, 11.5 or 12, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0105] The preparation process of the solid-phase precursor material is as follows:

[0106] S1. Lead oxide, lead salt, and copper oxide are mixed and ball-milled to obtain the first material, which is then mixed with copper salt to obtain the solid-phase precursor material.

[0107] Alternatively, S2, mix oxides, lead salts and copper salts to obtain solid-phase precursor materials;

[0108] In this invention, the oxide in S2 includes copper oxide and / or lead oxide.

[0109] Specifically, the molar ratio of lead oxide, lead salt, copper oxide and copper salt in S1 is (1-3):(0-1):(2-19 / 3):(1-8 / 3), for example, it can be 1:1:2:1, 2:1:5:2, 3:0.5:3:1, 2:0.5:3:2 or 3:0.75:4:1.5, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0110] Specifically, the molar ratio of Pb to Cu in the solid precursor material obtained in S1 is (7-9):(1-3), for example, it can be 7:1, 7:2, 7:3, 8:1, 8:2, 8:3, 9:1, 9:2 or 9:3, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0111] In S1, a planetary ball mill can be used for mixing, with a rotation speed of 300-400 r / min and a mixing time of ≥2 h. A dispersant can also be added to the mixing ball mill, with a material-to-dispersant mass ratio of 1:(3-10).

[0112] The rotation speed is 300-400 r / min, for example, it can be 300 r / min, 320 r / min, 340 r / min, 360 r / min, 380 r / min or 400 r / min, but it is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0113] The mixing time is ≥2h, for example, it can be 2h, 3h or 4h, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0114] The dispersant includes water, ethanol, isopropanol, and other commonly used dispersants in the art.

[0115] The mass ratio of the mixed material to the dispersant is 1:(3-10), for example, it can be 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0116] Specifically, the (Cu+Pb) / P molar ratio in the solid precursor obtained in S2 is 5 / 3, and the molar ratio of Pb / Cu is (7-10):(0-3).

[0117] Specifically, when the precursor material is a solid-phase precursor material, the solid-phase precursor material is mixed with a solvent before the first hydrothermal treatment to obtain a mixture before the first hydrothermal treatment.

[0118] The solid-liquid ratio of the solid-phase precursor and the solvent in the mixture is 1:(40-60) g / mL, for example, it can be 1:40, 1:42, 1:44, 1:46, 1:48, 1:50, 1:52, 1:54, 1:56, 1:58 or 1:60, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0119] The pH value of the mixture is 8-12, for example, it can be 8, 9, 10, 11 or 12, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0120] Specifically, the temperature of the first hydrothermal treatment is 60-80℃, for example, it can be 60℃, 65℃, 70℃, 75℃ or 80℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0121] Specifically, the stirring speed of the first hydrothermal process is 50-500 r / min, for example, it can be 50 r / min, 100 r / min, 200 r / min, 300 r / min, 400 r / min or 500 r / min, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0122] Specifically, the first hydrothermal time is 3-6 hours, for example, it can be 3 hours, 4 hours, 5 hours or 6 hours, but it is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0123] Specifically, the temperature of the second hydrothermal treatment is 150-180℃, for example, it can be 150℃, 155℃, 160℃, 165℃, 170℃, 175℃ or 180℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0124] Specifically, the second hydrothermal time is 6-24 hours, for example, it can be 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0125] In this invention, the heating methods in the first and second hydrothermal processes can be indirect heating methods such as water bath heating, oil bath heating, and sand bath heating, or direct heating methods such as thermocouples, microwaves, and electromagnetic heating.

[0126] Furthermore, to ensure the efficient conduct of the synthesis process, methods such as ultrasonic treatment can be used to enhance reaction efficiency.

[0127] Furthermore, the material after hydrothermal treatment undergoes solid-liquid separation before being roasted. The solid-liquid separation can be achieved using common separation methods in this field, such as evaporation, filtration, membrane filtration, pressure filtration, and centrifugation.

[0128] Membrane filtration can be selected from methods such as reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF).

[0129] The equipment used in filter press can be selected from belt filter press, plate and frame filter press, horizontal screw sedimentation centrifuge, chamber filter press, vertical hydraulic filter press, diaphragm machine and high pressure plate and frame machine, etc.

[0130] Furthermore, to facilitate the calcination process, the solid-liquid separated material can be shaped and pressed into blocks to obtain regular blanks for sintering.

[0131] The briquetting process can be carried out by cold pressing.

[0132] Specifically, the roasting temperature is 500-925℃, for example, it can be 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃ or 925℃, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0133] Specifically, the heating rate of the roasting is 5-8℃ / min, for example, it can be 5℃ / min, 5.5℃ / min, 6℃ / min, 6.5℃ / min, 7℃ / min, 7.5℃ / min or 8℃ / min, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0134] Specifically, the roasting time is 10-24 hours, for example, it can be 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0135] Furthermore, the roasting process provided by the present invention can be carried out under an atmosphere, which can be selected as argon atmosphere, nitrogen atmosphere, air atmosphere, mixed atmosphere of carbon monoxide and carbon dioxide, etc., and the roasting equipment used can be a high-temperature box furnace or tube furnace commonly used in the art.

[0136] Furthermore, to illustrate the superior properties of the copper-modified lead apatite obtained by the preparation method provided by the present invention, the following specific embodiments are provided for description:

[0137] Example 1

[0138] This embodiment provides a method for preparing copper-modified lead apatite. Taking a Pb / Cu molar ratio of 9 / 1 as an example, Pb9Cu1(PO4)6O is synthesized as follows:

[0139] (1) Dissolve 3.7261g of lead nitrate and 0.302g of copper nitrate in 100mL of deionized water and stir magnetically until fully dissolved.

[0140] (2) Add 0.9306g of Na2EDTA·H2O to the solution and mix thoroughly by magnetic stirring.

[0141] (3) Prepare a saturated NaOH solution, add it dropwise to the pre-prepared solution to form a precipitate, and stir continuously to adjust the pH to 10.

[0142] (4) Weigh 1.065g of NaH2PO4 powder and add it to the solution, and continue to use NaOH to adjust the pH to 10.

[0143] (5) Place the beaker in a water bath with a magnetic stirrer and stir at 400 r / min for 6 hours at 60°C. At this time, the color of the solution changes from grayish-green to dark brown.

[0144] (6) Pour the solution into a hydrothermal reactor and keep it at 150°C for 6 hours.

[0145] (7) After the hydrothermal treatment is completed, the powder is repeatedly rinsed with deionized water and then dried.

[0146] (8) Place the dried powder in a corundum crucible for calcination. The calcination temperature is set at 925℃, and the calcination heating rate is 5℃ / min. The calcination time is 10 hours.

[0147] (9) After the sample is taken out, it is placed in the air to cool naturally. After cooling, the sample turns silver-gray.

[0148] The resistance of the obtained samples was tested using a probe, with the samples either completely insulated or exceeding the measurement range. The XRD pattern of the calcined samples is shown below. Figure 2 As shown. The ZFC-FC curve of the sample is as follows. Figure 3 As shown, no obvious superconducting or ferromagnetic signals were observed. The sample exhibited a superposition of diamagnetism and ferromagnetism at 300 K at room temperature, as... Figure 4 As shown, the sample exhibits a suspected ferromagnetic signal, and this test result may be due to electron spin.

[0149] Example 2

[0150] This embodiment provides a method for preparing copper-modified lead apatite. Taking Pb / Cu = 9 / 1 as an example, Pb9Cu1(PO4)6O is synthesized as follows:

[0151] (1) Dissolve 3.7261g of lead nitrate and 0.302g of copper nitrate in 100mL of deionized water and stir magnetically until fully dissolved.

[0152] (2) Add 0.9306g of Na2EDTA·H2O to the solution and mix thoroughly by magnetic stirring.

[0153] (3) Prepare a saturated NaOH solution, add it dropwise to the pre-prepared solution to form a precipitate, and stir continuously to adjust the pH to 12.

[0154] (4) Weigh 1.065g of NaH2PO4 powder and add it to the solution, and continue to use NaOH to adjust the pH to 12.

[0155] (5) Place the beaker in a water bath with a magnetic stirrer and stir at 400 r / min for 6 hours at 60°C. At this time, the color of the solution changes from grayish-green to dark brown.

[0156] (6) Pour the solution into a hydrothermal reactor and keep it at 160°C for 6 hours.

[0157] (7) After the hydrothermal treatment is completed, the powder is repeatedly rinsed with deionized water and then dried.

[0158] (8) Place the dried powder in a corundum crucible for calcination. The calcination temperature is set at 925℃, and the calcination heating rate is 5℃ / min. The calcination time is 10 hours.

[0159] (9) After the sample is taken out, it is placed in the air to cool naturally. After cooling, the sample turns silver-gray.

[0160] The resistivity of the calcined samples was measured using a probe, and the sample resistivity was approximately 20-40 MΩ / cm. The XRD pattern of the calcined samples is shown below. Figure 5 As shown. The ZFC-FC curve of the sample is as follows. Figure 6 As shown, no obvious superconducting or ferromagnetic signals were observed. The sample exhibited a superposition of paramagnetism and ferromagnetism near room temperature, such as... Figure 7 As shown. After removing the paramagnetic backplane, the sample contained weak ferromagnetic impurities, which may be related to the trace amounts of copper oxides that failed to participate in the reaction, such as... Figure 8 As shown. Further, the EPR test was performed on the calcined sample, as shown... Figure 9 As shown, there is a distinct peak near 3300 Oe, which may be related to the Cu-O chain. Other peaks may be related to oxygen vacancies.

[0161] Example 3

[0162] This embodiment provides a method for preparing copper-modified lead apatite. Taking Pb / Cu = 9 / 1 as an example, Pb9Cu1(PO4)6O is synthesized as follows:

[0163] (1) Mix lead oxide, lead phosphate, and copper phosphate in a molar ratio of 3:8:1 and then place them in deionized water and stir at a stirring rate of 400 r / min. The actual amount added is 0.03 mol lead oxide, 0.08 mol copper phosphate, 0.01 mol copper nitrate, and 200 mL deionized water.

[0164] (2) Adjust the pH of the mixed liquid to 10 using NaOH.

[0165] (3) Place the beaker in a water bath with a magnetic stirrer and stir at 400 r / min for 6 hours at 60°C. At this time, the color of the solution changes from grayish-green to dark brown.

[0166] (4) Pour the solution into a hydrothermal reactor and keep it at 150°C for 6 hours.

[0167] (5) After the hydrothermal treatment is completed, the powder is repeatedly rinsed with deionized water and then dried.

[0168] (6) Place the dried powder in a corundum crucible for calcination. The calcination temperature is set at 900℃, and the calcination heating rate is 5℃ / min. The calcination time is 10 hours.

[0169] (7) After the sample is taken out, it is placed in the air to cool naturally. After cooling, the sample turns silver-gray.

[0170] The resistance of the calcined sample was tested using a probe, with the sample either completely insulated or exceeding the measurement range. The XRD pattern of the calcined sample is shown below. Figure 10 As shown. The ZFC-FC curve of the sample is as follows. Figure 11 As shown, no obvious superconducting or ferromagnetic signals were observed. The sample exhibited paramagnetism at low temperatures and diamagnetic behavior near room temperature, but the hysteresis loops did not completely coincide, as shown in the figure. Figure 12 As shown. Furthermore, the 300K hysteresis loop, after removing the diamagnetic bottom straight line, is as follows... Figure 13 As shown, the sample exhibits a suspected ferromagnetic signal, a result that could potentially be caused by electron spin. A very few peaks in the sample's XRD pattern point to the possible presence of a cubic structure similar to copper oxides. The ferromagnetic properties of some copper oxides have been noted in previous studies; this result could be due to instrumental error. Furthermore, the 10K hysteresis loop, after removing the paramagnetic base straight line, as shown... Figure 14 As shown, the sample exhibits a suspected superconducting magnetic signal, which may be due to residual Pb in the sample. x Cu y Materials such as O are common superconductors.

[0171] Examples 1-3 above describe three different methods for preparing copper-modified lead apatite, with slight differences between the methods. The XRD patterns of the three samples were compared, as follows: Figure 15 As shown, the purity of the products is high, but there are slight differences in their structure, which leads to significant differences in their magnetic properties.

[0172] Example 4

[0173] This embodiment provides a method for preparing copper-modified lead apatite. Taking Pb / Cu = 7 / 3 as an example, the specific steps for synthesizing Pb7Cu3(PO4)6O are as follows:

[0174] (1) Dissolve 2.8980g of lead nitrate and 0.906g of copper nitrate in 100mL of deionized water and stir magnetically until fully dissolved.

[0175] (2) Add 0.9306g of Na2EDTA·H2O to the solution and mix thoroughly by magnetic stirring.

[0176] (3) Prepare a saturated NaOH solution, add it dropwise to the pre-prepared solution to form a precipitate, and stir continuously to adjust the pH to 10.

[0177] (4) Weigh 1.065g of NaH2PO4 powder and add it to the solution, and continue to use NaOH to adjust the pH to 10.

[0178] (5) Place the beaker in a water bath with a magnetic stirrer and stir at 400 r / min for 6 hours at 60°C. At this time, the color of the solution changes from grayish-green to dark brown.

[0179] (6) Pour the solution into a hydrothermal reactor and keep it at 150°C for 6 hours.

[0180] (7) After the hydrothermal treatment is completed, the powder is repeatedly rinsed with deionized water and then dried.

[0181] (8) Place the dried powder in a corundum crucible for calcination. The calcination temperature is set at 925℃, and the calcination heating rate is 5℃ / min. The calcination time is 10 hours.

[0182] (9) After the sample is taken out, it is placed in the air to cool naturally. After cooling, the sample turns silver-gray.

[0183] The resistance of the calcined sample was tested using a probe, with the sample either completely insulated or exceeding the measurement range. The XRD pattern of the calcined sample is shown below. Figure 16 As shown, the lattice stability deteriorates when the Pb / Cu ratio is 7:3. The ZFC-FC curves of the samples are shown below. Figure 17As shown, no obvious superconducting or ferromagnetic signals were observed. The sample exhibited a superposition of diamagnetism and ferromagnetism at 300 K at room temperature, as... Figure 18 As shown, the sample exhibits a suspected ferromagnetic signal, and this test result may be due to electron spin.

[0184] The preparation methods for Examples 1 and 4 are the same, although there is a difference in the Pb / Cu molar ratio. The XRD patterns of the two are shown below. Figure 19 As shown, the crystal structures of the two are quite different. The methods in Examples 1 and 4 are the same, but the copper doping ratio differs, such as... Figure 20 The hysteresis loop shown indicates that the higher the copper doping ratio, the worse the ferromagnetism or spin, but the significantly improved the diamagnetism.

[0185] Example 5

[0186] The only difference from Example 1 is that the calcination was carried out under argon atmosphere and low vacuum (100 Pa), and the sample calcination temperature was 925°C. The sample calcination time was 24 hours, and the sample was water quenched after calcination.

[0187] Under an Ar atmosphere, some lead oxides undergo deoxidation, resulting in the formation of metallic Pb at the bottom of the sample. A pure Ar atmosphere is not conducive to the preparation of high-purity samples. After removing the small amount of Pb from the bottom, the XRD pattern of the calcined sample is as follows. Figure 21 As shown. The sample peak positions still correspond to the lead apatite structure, but the proportions of some peaks differ significantly. The sample exhibits a superposition of diamagnetism and ferromagnetism at 300K, as shown. Figure 22 and Figure 23 As shown. The sample exhibits a suspected ferromagnetic signal. After calcination, the sample demonstrates good conductivity. Resistance was measured using the four-electrode method; the upper surface resistance is low. The sample's connection and surface are shown in the image. Figure 24 As shown.

[0188] Because deoxidation occurs during calcination, the apatite structure adheres to the surface of metallic Pb. Around 6K, the sample exhibits a superconducting phase transition, which coincides with the superconducting transition temperature of metallic lead. Figure 25 As shown, the sample in channel 1 is metallic lead, and its resistance matches that of metallic lead. The RT curve for metallic Pb becomes a straight line after exceeding the superconducting transition temperature, which does not match the actual measurement results. We believe that an additional conductor exists in this phase and is connected in series with metallic Pb. This conductor exhibits the same conductivity as the metal at low temperatures, and its resistance increases linearly with temperature. However, a significant phase transition occurs around 250-280 K. Before the phase transition temperature, we consider the resistance of metallic lead to be A, and the resistance of the additional conductor to be B.

[0189] After removing resistors A and B, the sample resistance is as follows: Figure 26As shown, the resistance of the sample in channel 2 is significantly lower than that in channel 1, and also shows a linear increase, but a significant jump occurs around 300K, which may be due to testing errors. The test results for channel 2 are as follows... Figure 27 As shown.

[0190] After rewiring the sample, four resistance tests were performed, and the results are as follows. Figure 28-31 As shown, the sample exhibits a resistance jump at room temperature, transitioning towards a lower resistance. This may be related to a phase transition of a certain type of material, or the existence of a low-resistance conductor forming an equivalent circuit with Pb.

[0191] The lead apatite sample prepared by calcination according to the method of the present invention has high purity. The XRD pattern was refined by Materialsstudio, and the prepared sample conforms to random doping. The experimental value is basically consistent with the theoretical value.

[0192] Taking Example 3 as an example, after hydrothermal treatment, the sample obtained by solid-liquid separation was copper-doped lead hydroxyapatite. After refinement, the theoretical and calculated values ​​were in high agreement. The refined XRD pattern of the sample after hydrothermal treatment is shown below. Figure 32 As shown.

[0193] The calcined sample obtained in Example 3, after XRD refinement, is as follows: Figure 33 As shown. A schematic diagram of the structure of Example 3 is shown below. Figure 34 As shown.

[0194] Furthermore, the XRD refinement results of the samples from Examples 1 and 4 are detailed in [reference needed]. Figure 35 and Figure 36 .

[0195] The preparation method provided by this invention, by treating the rationally designed raw materials through a specific hydrothermal process, can obtain copper-modified lead apatite with extremely low impurity content, which is beneficial to broadening the application field of copper-modified lead apatite and improving its performance.

[0196] The present invention is described in detail through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0197] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0198] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0199] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A preparation method of copper-modified lead phosphate apatite, characterized in that, The preparation method includes the following steps: Subjecting the precursor material to first hydrothermal treatment and then second hydrothermal treatment in sequence, and then obtaining copper-modified lead phosphate through calcination; The precursor material includes a liquid-phase precursor material or a solid-phase precursor material; The liquid-phase precursor material is obtained by mixing a lead salt, a copper salt, a phosphorus source, a pH adjuster, a chelating agent and a solvent; The solid-phase precursor material is obtained by mixing a copper compound and a lead compound; The temperature of the first hydrothermal treatment < the temperature of the second hydrothermal treatment; The preparation process of the liquid-phase precursor material is as follows: Prepare a solution from a lead salt, a copper salt, a chelating agent and a solvent, then adjust the pH value using a pH adjuster, and then add a phosphorus source to obtain the liquid-phase precursor material; The temperature of the first hydrothermal treatment is 60 - 80 °C; The temperature of the second hydrothermal treatment is 150 - 180 °C.

2. The preparation method of copper-modified lead phosphate as claimed in claim 1, wherein, The total concentration of copper and lead elements in the prepared solution is 0.1 - 0.15 mol / L.

3. The preparation method of copper-modified lead phosphate apatite according to claim 1, wherein The addition amount of the chelating agent is 1 - 1.1 times the total concentration of copper and lead elements in the solution.

4. The preparation method of copper-modified lead phosphate as claimed in claim 1, wherein The end pH value of the pH adjustment is 8 - 12.

5. The preparation method of the copper-modified lead phosphate apatite according to claim 1, wherein The molar ratio of (Cu + Pb) / P in the liquid-phase precursor material is (1.5 - 1.7):

1.

6. The preparation method of copper-modified lead phosphate apatite according to claim 1, characterized in that, The pH value of the liquid-phase precursor material is 8 - 12.

7. The preparation method of copper-modified lead phosphate apatite according to claim 1, wherein The preparation process of the solid-phase precursor material is as follows: S1. Mix and ball-mill lead oxide, lead salt, and copper oxide to obtain a first material, and then mix it with a copper salt to obtain the solid-phase precursor material; Or, S2. Mix an oxide, a lead salt and a copper salt to obtain the solid-phase precursor material; the oxide in S2 includes copper oxide and / or lead oxide.

8. The preparation method of copper-modified lead phosphate apatite according to claim 7, characterized in that, In S1, the molar ratio of the lead oxide, lead salt, copper oxide and copper salt is (1 - 3):(0 - 1):(2 - 19 / 3):(1 - 8 / 3).

9. The preparation method of the copper-modified lead phosphate apatite according to claim 1, wherein, In S1, the molar ratio of Pb to Cu in the obtained solid-phase precursor material is (7 - 9):(1 - 3).

10. The preparation method of the copper-modified lead phosphate apatite according to claim 1, wherein, When the precursor material is a solid-phase precursor material, before the first hydrothermal treatment, mix the solid-phase precursor material with a solvent to obtain a mixed material and then perform the first hydrothermal treatment.

11. The preparation method of copper-modified lead phosphate apatite according to claim 1, characterized in that, The solid-liquid ratio g / mL of the solid-phase precursor material and the solvent is 1:(40 - 60).

12. The preparation method of the copper-modified lead phosphate apatite according to claim 10, wherein, The pH value of the mixed material is 8 - 12.

13. The preparation method of the copper-modified lead phosphate as claimed in claim 11, wherein The time of the first hydrothermal treatment is 3 - 6 h.

14. The preparation method of the copper-modified lead phosphate apatite according to claim 1, wherein, The time of the second hydrothermal treatment is 6 - 24 h.

15. The preparation method of copper-modified lead phosphate as claimed in claim 1, wherein The temperature of the calcination is 500 - 925 °C.

16. The preparation method of copper-modified lead phosphate apatite according to claim 1, wherein, The time of the calcination is 10 - 24 h.

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