A method for preparing carbide microspheres

Abstract

The application provides a preparation method of metal carbide microspheres, and belongs to the technical field of micro-nano materials. The method comprises the following steps: alloy powder smelting, alloy powder preparation, alloy powder screening, a metal matrix corrosion process, a cleaning process and a screening process, so that a metal carbide micro-nano spherical material is obtained. The metal carbide microspheres can be applied in the fields including but not limited to nuclear materials, energy materials and metal matrix composites. The size of the metal carbide microspheres prepared by the application can be customized in the range of 10-300 um through screening, the average thickness of metal carbide dendrites is 1-20 nm, the average dendrite spacing of the carbide is 1-5 um, and the composition of the metal carbide microspheres can be controlled by alloy composition.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of micro-nano materials, and particularly relates to a preparation method of carbide microspheres. BACKGROUND

[0002] The size effect of micro-nano materials increases the specific surface area and obtains some novel properties, and thus has been a research hotspot. Metal carbide materials have the advantages of high melting point, high hardness and corrosion resistance, and are widely used for preparing metal matrix composites, wear-resistant materials, corrosion-resistant materials, electronic component related materials and new energy materials. Micro-nano metal carbide spheres are expected to be applied in the fields of aerospace, energy materials, electrochemical catalysis and the like.

[0003] In the prior art, the preparation of micro-nano metal carbide is to dip metal salt on high specific surface area carbon microspheres, and then to obtain micro-nano metal carbide through hydrothermal reaction and vacuum treatment. For example, the patent document with the publication number CN114180965 discloses a preparation method of high-entropy carbide nano powder, which is to perform vacuum heat treatment on the carbide microspheres immersed in the metal salt solution to load metal oxides, and to perform hydrothermal reaction on the carbon microspheres loaded with metal salt to obtain nano powder. However, the method has high complexity, requires a large number of equipment, and needs a long preparation time for batch preparation. Moreover, the preparation of carbide microspheres, the preparation of precursors and the final separation and generation steps all need multiple heating treatments, which is not conducive to energy saving.

[0004] In the prior art, another method is to press and sinter metal oxides, carbon powder and magnesium powder to form pores to obtain high-entropy carbide ceramic nano powder. For example, the patent with the publication number CN113620712A discloses a preparation technology of high-entropy carbide nano ceramic powder, which is to sinter complex metal oxides, carbon powder, magnesium powder and NaF into a block and then to corrode to obtain high-entropy carbide material. Since oxides are used for sintering, and the high-entropy carbide is in a spherical shape, only the surface of the carbide that contacts the corrosion liquid can be corroded in the corrosion step, and the oxides embedded in the innermost part cannot be fully corroded. The minimum oxygen impurity content in the finished product is 2.55%, and the properties of high-entropy carbide are easily affected by oxygen impurities.

[0005] Therefore, it is necessary to provide a preparation method of carbide microspheres characterized by nanoscale width dendrites. SUMMARY

[0006] Therefore, the present application provides a preparation method of carbide microspheres, which can save energy, quickly manufacture and not be affected by oxides.

[0007] To solve the above technical problems, the present application provides a kind of metal alloy for preparing carbide microspheres, comprising the following components, the metal alloy includes matrix element A, carbide forming element B and carbon element C, the content of the carbide forming element B is 2.0-45.0 wt.%, the content of the carbon element C is 0.5-5.0 wt.%, and the rest is element A;

[0008] The matrix element A is one of Fe, Al, Ni, Co, Ti, Cu, Mo or a combination of two or more thereof, and the carbide forming element B is one of Ti, Zr, V, Ta, Nb, W, Mo, Cr, Mn, Fe, Si, B, Hf or a combination of two or more thereof.

[0009] The carbide microspheres finally formed using the above alloy composition will form carbide microspheres with perfect spherical shape in the case of uniform texture, as shown in Figure 4 and Figure 6 The surface area of the carbide microspheres prepared by late-stage corrosion is large, the spherical shape is perfect, and the pores of the prepared microspheres are more distinct and uniform compared to the two methods of the prior art.

[0010] Further, another object of the present application is to provide a method for preparing carbide microspheres, comprising the following steps:

[0011] The alloy powder is prepared according to the metal alloy composition of claim 1, the alloy powder is dispersed in liquid phase to obtain an alloy powder dispersion phase, the corrosion liquid is added into the alloy powder dispersion phase, and the reaction is carried out to obtain the carbide microspheres.

[0012] The present application first melts the metal components, carbide elements and carbon elements into a homogeneous alloy material, and then mills the alloy material. Compared with the first method of loading metal salt solution on the existing carbide microspheres and evaporating water to carry out hydrothermal reaction, the present application can greatly prepare batches of carbide microspheres, saving energy. Compared with the second method of producing carbide microspheres by pressing and sintering and corrosion, the performance of the carbide microspheres produced by the second method does not meet the demand of higher aerospace and energy material field due to the presence of oxides. The carbide microspheres prepared by the present application do not contain oxides.

[0013] Further, the alloy powder is prepared by using ball milling, the ball milling speed is 200-500 rpm, and the crushing time is 30-240 min.

[0014] Further, the alloy powder needs to be preliminarily screened before the liquid phase dispersion, and the average particle size of the preliminarily screened alloy powder is 10 nm-300 μm.

[0015] Furthermore, the liquid phase in the liquid-phase dispersion is anhydrous ethanol, and the volume ratio of the alloy powder to the anhydrous ethanol is 1:5~50.

[0016] Furthermore, when the matrix element A is Fe or Ni, the etching solution is aqua regia; when the matrix element A is Al, Co, or Cu, the etching solution is hydrochloric acid or nitric acid; when the matrix element A is Ti, the etching solution is sulfuric acid.

[0017] Furthermore, after the alloy powder undergoes the preliminary screening, if the average particle size of the alloy powder is 1~300 μm, the standing time shall be no less than 12h; if the average particle size of the alloy powder is 10~1000 nm, the standing time shall be no less than 24h.

[0018] Furthermore, the carbide microspheres after the corrosion solution reaction need to be cleaned. The cleaning agent for cleaning the carbide microspheres is anhydrous ethanol, and the volume ratio of the anhydrous ethanol to the settled alloy powder mixture is 1~3:1.

[0019] Furthermore, the carbide microspheres, after being cleaned, are dried at a temperature of 60-90°C for 1-4 hours.

[0020] Furthermore, the alloy powder needs to be heat-treated before liquid-phase dispersion. The heat treatment requires sealing protection, which is achieved by sealing with a glass tube or a metal sleeve. After sealing, the alloy powder is placed in a heat treatment furnace and modified under an inert gas atmosphere. The heating rate is 10 °C / min, the aging temperature is 600~1200 °C, and the aging time is 30~240 min. Attached Figure Description

[0021] Figure 1 This is a backscattered micrograph of the cross-section of the metal powder in Embodiment 1 of the present invention;

[0022] Figure 2 for Figure 1 Further magnification of these dendritic structures in the micrographs;

[0023] Figure 3 The image shows the EDS energy spectrum of the dendritic structure in Embodiment 1 of the present invention.

[0024] Figure 4 This is a schematic diagram of a carbide microsphere characterized by nanoscale-width dendrites prepared according to Embodiment 1 of the present invention;

[0025] Figure 5 This is a schematic diagram of the carbide microspheres prepared in Comparative Example 1 of the present invention;

[0026] Figure 6A schematic view of the carbide microspheres prepared in Example Six of the present application. DETAILED DESCRIPTION

[0027] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the following will combine the drawings of the embodiments of the present application to make a better description. Figures 1-6 The technical solutions of the embodiments of the present application are described clearly and completely. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by those skilled in the art belong to the scope of protection of the present application.

[0028] Example One

[0029] This embodiment is to prepare carbide microspheres with a particle size of less than 10 μm, including the following steps:

[0030] S1, component design

[0031] The alloy component design is as follows: C: 1.6, W: 10.0, Mo: 3.0, Cr: 5.0, V: 5.0, and Fe is supplemented to 100. Among them, the base material is Fe element, and the carbide forming elements are V element and W element;

[0032] S2, alloy smelting

[0033] The alloy ingredients are designed to be dosed (considering the loss of elements in the smelting process), and the alloy ingredients are smelted in a medium-frequency furnace to obtain alloy raw materials with qualified components;

[0034] S3, powder preparation

[0035] The alloy raw materials are rusted and cut into fragments, the alloy is smelted and atomized into metal powder by gas atomization powder preparation equipment, the atomizing gas medium is high-purity nitrogen, and the gas pressure is 20 MPa.

[0036] S4, powder pretreatment

[0037] The prepared alloy powder is screened, and the alloy powder with a particle size of less than 15 μm is screened out.

[0038] S5, powder corrosion

[0039] The iron base is corroded using aqua regia (salt: nitric acid = 3:1), the pretreated alloy powder is placed in a corrosion-resistant container, anhydrous ethanol is used to disperse the alloy powder, in order to improve the reaction efficiency, a constant temperature heating table set at 60 ℃ and ultrasonic vibration are used, the aqua regia is gradually added to the corrosion-resistant container until the reaction is completed, and the mixture is left to stand for 24 h.

[0040] S6, powder post-treatment

[0041] The upper layer of the etching solution is removed, and the residual product is washed 5 times using anhydrous ethanol at a volume ratio of 1:2;

[0042] The product is dried using an oven at a temperature of 80°C for 3h to obtain micro-nano carbide microspheres.

[0043] Example Two

[0044] The difference between this example and Example One is the difference in alloy composition, which increases the proportion of C element.

[0045] This example is to prepare carbide microspheres with a particle size of less than 10 μm, including the following steps:

[0046] S1, component design

[0047] The alloy composition is designed as follows: C: 1.29, W: 6.3, Mo: 5.0, Cr: 4.2, V: 3.0, and Fe is supplemented to 100. Among them, the base material is Fe element, and the carbide forming elements are V element and W element;

[0048] S2, alloy smelting

[0049] The alloy ingredients are designed by considering the loss of elements in the smelting process, and the alloy ingredients are smelted in a medium-frequency furnace to obtain alloy raw materials with qualified components;

[0050] S3, powder preparation

[0051] The alloy raw material is rusted and cut into fragments, and the alloy is smelted and atomized into metal powder by gas atomization powder preparation equipment. The gas medium is high-purity nitrogen, and the gas pressure is 20 MPa.

[0052] S4, powder pretreatment

[0053] The prepared alloy powder is sieved to screen out alloy powder with a particle size of less than 15 μm.

[0054] S5, powder etching

[0055] The iron base is etched using aqua regia (hydrochloric acid: nitric acid = 3:1), the pretreated alloy powder is placed in a corrosion-resistant container, anhydrous ethanol is used to disperse the alloy powder, a constant temperature heating table set at 60°C and ultrasonic vibration are used to improve the reaction efficiency, and aqua regia is gradually added to the corrosion-resistant container until the reaction is complete, and then it is left to stand for 24h;

[0056] S6, powder post-treatment

[0057] The upper layer of the etching solution is removed, and the residual product is washed 5 times using anhydrous ethanol at a volume ratio of 1:2;

[0058] The product was dried in an oven at 80°C for 3 hours to obtain micro-nano carbide microspheres.

[0059] Example 3

[0060] The difference between this embodiment and Embodiment 1 lies in the alloy composition, which increases the proportion of carbon.

[0061] This embodiment describes the preparation of carbide microspheres with a particle size of less than 10 μm, and includes the following steps:

[0062] S1, Ingredient Design

[0063] The alloy composition is designed as follows: C: 1.64, W: 12.4, Mo: 0.5, Cr: 4.4, V: 4.9, and Fe to be rounded up to 100. The matrix material is Fe, and the carbide-forming elements are V and W.

[0064] S2, Alloy Smelting

[0065] The alloy composition is designed for batching (considering the loss of elements during the smelting process), and the alloy batches are smelted in an intermediate frequency furnace to obtain alloy raw materials with qualified composition.

[0066] S3, Powder Preparation

[0067] The alloy raw materials are derusted and cut into small pieces. The alloy is then smelted and atomized into metal powder using a gas atomization powder making equipment. The atomizing gas medium is high-purity nitrogen, and the gas pressure is 20 MPa.

[0068] S4, Powder Pretreatment

[0069] The prepared alloy powder was sieved to remove alloy powder with a particle size of less than 15 μm.

[0070] S5, Powder Corrosion

[0071] The iron matrix was corroded using aqua regia (hydrochloric acid: nitric acid = 3:1). The pretreated alloy powder was placed in a corrosion-resistant container and dispersed with anhydrous ethanol. To improve the reaction efficiency, a constant temperature heating table set to 60°C and ultrasonic vibration were used to gradually add aqua regia to the corrosion-resistant container until the reaction was completed and then allowed to stand for 24 hours.

[0072] S6. Powder Post-processing

[0073] Remove the upper corrosive liquid, and wash the remaining product five times with anhydrous ethanol at a volume ratio of 1:2.

[0074] The product was dried in an oven at 80°C for 3 hours to obtain micro-nano carbide microspheres.

[0075] Example 4

[0076] The difference between this embodiment and Embodiment 1 lies in the alloy composition, which increases the proportion of carbon.

[0077] This embodiment describes the preparation of carbide microspheres with a particle size of less than 10 μm, and includes the following steps:

[0078] S1, Ingredient Design

[0079] The alloy composition is designed as follows: C: 2.0, W: 14.3, Mo: 2.5, Cr: 3.8, V: 5.1, Fe to be rounded up to 100. The matrix material is Fe, and the carbide-forming elements are V and W.

[0080] S2, Alloy Smelting

[0081] The alloy composition is designed for batching (considering the loss of elements during the smelting process), and the alloy batches are smelted in an intermediate frequency furnace to obtain alloy raw materials with qualified composition.

[0082] S3, Powder Preparation

[0083] The alloy raw materials are derusted and cut into small pieces. The alloy is then smelted and atomized into metal powder using a gas atomization powder making equipment. The atomizing gas medium is high-purity nitrogen, and the gas pressure is 20 MPa.

[0084] S4, Powder Pretreatment

[0085] The prepared alloy powder was sieved to remove alloy powder with a particle size of less than 15 μm.

[0086] S5, Powder Corrosion

[0087] The iron matrix was corroded using aqua regia (hydrochloric acid: nitric acid = 3:1). The pretreated alloy powder was placed in a corrosion-resistant container and dispersed with anhydrous ethanol. To improve the reaction efficiency, a constant temperature heating table set to 60°C and ultrasonic vibration were used to gradually add aqua regia to the corrosion-resistant container until the reaction was completed and then allowed to stand for 24 hours.

[0088] S6. Powder Post-processing

[0089] Remove the upper corrosive liquid, and wash the remaining product five times with anhydrous ethanol at a volume ratio of 1:2.

[0090] The product was dried in an oven at 80°C for 3 hours to obtain micro-nano carbide microspheres.

[0091] Example 5

[0092] The difference between this embodiment and Embodiment 1 lies in the alloy composition, which increases the proportion of carbon.

[0093] This embodiment describes the preparation of carbide microspheres with a particle size of less than 10 μm, and includes the following steps:

[0094] S1, Ingredient Design

[0095] The alloy composition is designed as follows: C: 2.3, W: 6.5, Mo: 7.0, Cr: 4.2, V: 6.5, Fe to 100. The matrix material is Fe, and the carbide-forming elements are V and W.

[0096] S2, Alloy Smelting

[0097] The alloy composition is designed for batching (considering the loss of elements during the smelting process), and the alloy batches are smelted in an intermediate frequency furnace to obtain alloy raw materials with qualified composition.

[0098] S3, Powder Preparation

[0099] The alloy raw materials are derusted and cut into small pieces. The alloy is then smelted and atomized into metal powder using a gas atomization powder making equipment. The atomizing gas medium is high-purity nitrogen, and the gas pressure is 20 MPa.

[0100] S4, Powder Pretreatment

[0101] The prepared alloy powder was sieved to remove alloy powder with a particle size of less than 15 μm.

[0102] S5, Powder Corrosion

[0103] The iron matrix was corroded using aqua regia (hydrochloric acid: nitric acid = 3:1). The pretreated alloy powder was placed in a corrosion-resistant container and dispersed with anhydrous ethanol. To improve the reaction efficiency, a constant temperature heating table set to 60°C and ultrasonic vibration were used to gradually add aqua regia to the corrosion-resistant container until the reaction was completed and then allowed to stand for 24 hours.

[0104] S6. Powder Post-processing

[0105] Remove the upper corrosive liquid, and wash the remaining product five times with anhydrous ethanol at a volume ratio of 1:2.

[0106] The product was dried in an oven at 80°C for 3 hours to obtain micro-nano carbide microspheres.

[0107] Example 6

[0108] The difference between this embodiment and Embodiment 1 is that alloy powder with a smaller particle size was selected for preparation.

[0109] A method for preparing micro / nano carbide microspheres, in this example for preparing carbide microspheres with a particle size of less than 10 μm, includes the following steps:

[0110] S1, Ingredient Design

[0111] To prepare the required carbide microspheres, the alloy composition was designed as follows: C: 1.6, W: 10.0, Mo: 3.0, Cr: 5.0, V: 5.0, and Fe to 100. The matrix material is Fe, and the carbide-forming elements are V and W.

[0112] S2, Alloy Smelting

[0113] The alloy composition is designed for batching (considering the loss of elements during the smelting process), and the alloy batches are smelted in an intermediate frequency furnace to obtain alloy raw materials with qualified composition.

[0114] S3, Powder Preparation

[0115] The alloy raw materials are derusted and cut into small pieces. These pieces are then smelted and atomized into metal powder using a gas atomization powder-making device. The atomizing gas medium is high-purity nitrogen, and the gas pressure is 10~20 MPa. S4. Powder Pretreatment

[0116] S4, Powder Pretreatment

[0117] The prepared alloy powder was sieved to remove alloy powder with a particle size of less than 5 μm.

[0118] S5, Powder Corrosion

[0119] The iron matrix was corroded using aqua regia (hydrochloric acid: nitric acid = 3:1). The pretreated alloy powder was placed in a corrosion-resistant container and dispersed with anhydrous ethanol. To improve the reaction efficiency, a constant temperature heating table set to 60°C and ultrasonic vibration were used to gradually add aqua regia to the corrosion-resistant container until the reaction was completed and then allowed to stand for 24 hours.

[0120] S6. Powder Post-processing

[0121] Remove the upper corrosive solution and wash the remaining product five times with anhydrous ethanol.

[0122] The product was dried in an oven at 80°C for 3 hours to obtain micro-nano carbide microspheres.

[0123] Comparative Example 1

[0124] The difference between this comparative example and Example 1 is that the standing time after adding the etchant is shortened.

[0125] A method for preparing micro / nano carbide microspheres, in this example for preparing carbide microspheres with a particle size of less than 10 μm, includes the following steps:

[0126] S1, Ingredient Design

[0127] To prepare the required carbide microspheres, the alloy composition was designed as follows: C: 1.6, W: 10.0, Mo: 3.0, Cr: 5.0, V: 5.0, and Fe to 100. The matrix material is Fe, and the carbide-forming elements are V and W.

[0128] S2, Alloy Smelting

[0129] The alloy composition is designed for batching (considering the loss of elements during the smelting process), and the alloy batches are smelted in an intermediate frequency furnace to obtain alloy raw materials with qualified composition.

[0130] S3, Powder Preparation

[0131] The alloy raw materials are derusted and cut into small pieces. The alloy is then smelted and atomized into metal powder using a gas atomization powder making equipment. The atomizing gas medium is high-purity nitrogen, and the gas pressure is 10~20 MPa.

[0132] S4, Powder Pretreatment

[0133] The prepared alloy powder was sieved to remove alloy powder with a particle size of less than 15 μm.

[0134] S5, Powder Corrosion

[0135] The iron matrix was corroded using aqua regia (hydrochloric acid: nitric acid = 3:1). The pretreated alloy powder was placed in a corrosion-resistant container, and the alloy powder was dispersed using anhydrous ethanol. Aqua regia was gradually added to the corrosion-resistant container and allowed to stand for 2 hours.

[0136] S6. Powder Post-processing

[0137] Remove the upper corrosive solution and wash the remaining product five times with anhydrous ethanol.

[0138] The product was dried in an oven at 80°C for 3 hours to obtain micro-nano carbide microspheres.

[0139] analyze:

[0140] The carbide microspheres prepared in Example 1 were scanned by electron microscopy. Figure 1 The image shows a cross-section of a metal powder under backscattered microscopy, revealing a large number of bright white dendritic structures within the powder.

[0141] Figure 2To further magnify these dendritic structures, it can be seen that the width of the dendritic structure is about 200 nm and the dendrite spacing is about 4 μm.

[0142] Figure 3 The EDS spectrum of the dendritic structure shows that it contains a high proportion of carbon and strong carbide-synthesizing elements V and W, therefore the dendritic structure is a carbide.

[0143] Figure 4 The example shown is a carbide microsphere characterized by nanoscale-width dendrites, which was finally prepared in Example 1.

[0144] In Example 6, Figure 6 To ultimately prepare a carbide microsphere characterized by nanoscale dendrites, the microspheres in Examples 1 and 6 are perfectly shaped, have a uniform alloy material texture, and have a large surface area. Compared with the two methods in the prior art, the microspheres prepared have distinct and uniform pores.

[0145] In Comparative Example 1, Figure 5 The main reason for the failure to prepare carbide microspheres was the low reaction efficiency and insufficient reaction time under the case conditions. Compared with Example 1 and Example 6, the microspheres of Comparative Example 1 had almost no pores, and the spheres were of different sizes, not round, and had uneven shape and texture.

[0146] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing carbide microspheres, characterized in that, Includes the following steps: The metal alloy comprises a matrix element A, a carbide-forming element B, and carbon element C, wherein the content of the carbide-forming element B is 2.0 ~ 45.0 wt.%, the content of the carbon element C is 0.5 ~ 5.0 wt.%, and the remainder is element A; The matrix element A is one or more of Fe, Al, Ni, Co, Ti, Cu, and Mo, and the carbide forming element B is one or more of Ti, Zr, V, Ta, Nb, W, Mo, Cr, Mn, Fe, Si, B, and Hf. Alloy powder is prepared according to the metal alloy composition, and the alloy powder is dispersed in the liquid phase to obtain an alloy powder dispersion phase. Corrosion liquid is added to the alloy powder dispersion phase, and carbide microspheres are obtained by reaction. The alloy powder is prepared by melting the alloy and atomizing it into metal powder using a gas atomization powder preparation equipment. The atomizing gas medium is high-purity nitrogen.

2. The method for preparing carbide microspheres as described in claim 1, characterized in that, The alloy powder before liquid phase dispersion needs to be pre-screened, and the average particle size of the pre-screened alloy powder is 10 nm ~ 300 μm.

3. The method for preparing carbide microspheres as described in claim 1, characterized in that, The liquid phase in the liquid-phase dispersion is anhydrous ethanol, and the volume ratio of the alloy powder to the anhydrous ethanol is 1:5 to 50.

4. The method for preparing carbide microspheres as described in claim 1, characterized in that, When the matrix element A is Fe or Ni, the etching solution is aqua regia; when the matrix element A is Al, Co or Cu, the etching solution is hydrochloric acid or nitric acid; when the matrix element A is Ti, the etching solution is sulfuric acid.

5. The method for preparing carbide microspheres as described in claim 2, characterized in that, After the alloy powder undergoes the preliminary screening, if the average particle size of the alloy powder is 1~300 μm, the standing time shall not be less than 12h; if the average particle size of the alloy powder is 10~1000 nm, the standing time shall not be less than 24h.

6. The method for preparing carbide microspheres as described in claim 1, characterized in that, The carbide microspheres after the corrosion solution reaction need to be cleaned. The cleaning agent for cleaning the carbide microspheres is anhydrous ethanol, and the volume ratio of the anhydrous ethanol to the settled alloy powder mixture is 1~3:

1.

7. The method for preparing carbide microspheres as described in claim 6, characterized in that, The carbide microspheres, after being cleaned, are dried at a temperature of 60-90°C for 1-4 hours.

8. The method for preparing carbide microspheres as described in claim 1, characterized in that, The alloy powder needs to be heat-treated before liquid-phase dispersion. The heat treatment requires sealing protection, which is achieved by sealing with a glass tube or a metal sleeve. After sealing, the alloy powder is placed in a heat treatment furnace and modified under an inert gas atmosphere. The heating rate is 10 °C / min, the aging temperature is 600 ~ 1200 °C, and the aging time is 30 ~ 240 min.

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