Cooking utensil and preparation method thereof

Abstract

The invention relates to a cooking utensil and a preparation method thereof. The cooking utensil comprises a cooking container provided with a cooking cavity, the cooking container comprises a porous ceramic matrix, a glaze layer and a carbon film, the glaze layer is attached to the inner surface and the outer side wall of the porous ceramic matrix, and the absolute value of the difference value of the thermal expansion coefficient of the glaze layer and the thermal expansion coefficient of the porous ceramic matrix is smaller than or equal to 3 * 10 <-6 > / DEG C; the carbon film is attached to the bottom of the outer surface of the porous ceramic matrix and permeates inwards to form a carbon-containing area, the thickness of the porous ceramic matrix is taken as H, in the carbon-containing area, the carbon content of the outer surface of the porous ceramic matrix is larger than or equal to 10 wt%, the carbon content at the H / 2 position is larger than or equal to 3 wt%, and the carbon content of the carbon-containing area is gradually decreased from the outer surface of the porous ceramic matrix to the direction close to the inner surface. The cooking utensil has excellent heat conduction performance, cold and hot impact resistance and heat preservation and heat storage performance.

Description

Technical Field

[0001] The present invention relates to the technical field of daily necessities, in particular to a cooking vessel and a preparation method thereof. Background Art

[0002] Daily-use ceramics generally have aluminum oxide and silicon oxide as the main components, and are usually made by spinning and sintering materials such as clay and kaolin. The thermal conductivity coefficient is generally 0.5W / mK-3W / mK, and the heat transfer efficiency is extremely low. As a result, when ceramic utensils are used in small household appliances such as electric stew pots and rice cookers, there are problems such as low energy efficiency, slow heat transfer, and long usage time.

[0003] However, it is extremely difficult to improve the thermal conductivity of ordinary ceramics. Conventionally adding high thermal conductivity substances to ceramic materials will affect the strength, heat resistance and other properties of the ceramics themselves. The use of high thermal conductivity materials, such as pure alumina, silicon carbide, etc., is not only extremely expensive, but also difficult to form, and is difficult to apply to the small household appliance industry. Even if the high thermal conductivity material is mixed with the matrix material for molding, the high thermal conductivity material is easily mixed unevenly with the matrix material, resulting in uneven distribution of the high thermal conductivity material, resulting in unstable performance, and the thermal shock resistance drops sharply after molding.

[0004] In addition, existing heat-resistant ceramics usually need to add spodumene to reduce the thermal expansion coefficient and improve resistance to thermal shock. However, the price of lithium ore has skyrocketed in recent years, resulting in a continuous increase in the cost of heat-resistant ceramics.

[0005] Therefore, it is necessary to develop a ceramic vessel that has high thermal conductivity and resistance to thermal shock and takes into account its own thermal insulation and heat storage performance. Summary of the invention

[0006] Based on this, it is necessary to provide a cooking vessel and a preparation method thereof to address the above problems; the cooking vessel not only has excellent thermal conductivity and resistance to cold and heat shock, but also can maintain good thermal insulation and heat storage performance. Using it as a cooking utensil is highly safe and conducive to improving the overall energy efficiency utilization rate.

[0007] A cooking vessel for a cooking utensil, comprising a cooking container provided with a cooking cavity, the cooking container comprising a porous ceramic substrate, a glaze layer and a carbon film;

[0008] The absolute value of the difference between the thermal expansion coefficient of the glaze layer and the thermal expansion coefficient of the porous ceramic matrix is ​​less than or equal to 3×10 -6 / ℃;

[0009] The carbon film is attached to the bottom of the outer surface of the porous ceramic substrate and penetrates inward to form a carbon-containing zone. The thickness of the porous ceramic substrate is denoted as H. In the carbon-containing zone, the carbon content of the outer surface of the porous ceramic substrate is greater than or equal to 10wt%, the carbon content at H / 2 is greater than or equal to 3wt%, and the carbon content of the carbon-containing zone decreases from the outer surface of the porous ceramic substrate to the inner surface.

[0010] In the cooking vessel of the present invention, the surface of the porous ceramic substrate has a glaze layer and a regionally distributed carbon film, and the interior has a carbon-containing area with selectively gradient distributed carbon, and the glaze layer and the porous ceramic substrate satisfy a specific thermal expansion coefficient relationship. This special structure has many performance advantages: first, by reducing the porosity and defects of the cooking container, reducing the thermal resistance in the heat transfer process, and forming a carbide phase in the porous ceramic matrix, changing the crystal structure, and improving the thermal conductivity, the thermal conductivity of the cooking container reaches 5W / (m·K)-10W / (m·K); second , it can ensure that the cooking utensils still have good heat preservation and heat storage performance on the basis of greatly improving the thermal conductivity, thereby improving the comprehensive energy efficiency utilization rate; thirdly, the glaze layer and carbon film on the surface are conducive to enhancing the interface bonding and interface stability of the ceramic material, alleviating the generation and propagation of thermal stress and thermal shock, and the carbon film is also conducive to the uniform transfer of heat, which can avoid the generation of large temperature gradients and reduce the thermal stress caused by thermal shock, thereby reducing the risk of crack formation and rupture, and is particularly suitable for improving the thermal shock resistance in the case of a ceramic matrix that does not contain spodumene. In addition, the cooking utensils described in the present invention not only have the above-mentioned performance advantages, but also overcome the practical application problems of traditional carbon-based cooking utensils such as blackening and unsightly appearance.

[0011] In one embodiment, the carbon film has a thickness of 1 μm-20 μm.

[0012] By precisely controlling the thickness of the carbon film, it is helpful to further improve the thermal conductivity and resistance to thermal shock.

[0013] In one embodiment, the cooking container satisfies at least one of the following conditions:

[0014] (1) The carbon content in the range of thickness H / 4 extending from the outer surface of the porous ceramic substrate to the inner surface thereof is 5wt%-13wt%;

[0015] (2) the carbon content in the range of H / 2 extending from the thickness of H / 4 toward the outer surface of the porous ceramic substrate is 3wt%-5wt%;

[0016] (3) The carbon content in the cooking container is 5wt%-10wt%.

[0017] By regulating the specific distribution of the carbon content in the cooking container, it is helpful to further improve the thermal conductivity.

[0018] In one embodiment, the glaze layer satisfies at least one of the following conditions:

[0019] (1) The thermal expansion coefficient of the glaze layer is 2×10 -4 / ℃-7×10 -4 / ℃;

[0020] (2) The thickness of the glaze layer is 20 μm-500 μm;

[0021] (3) The porosity of the glaze layer is less than 1%;

[0022] (4) The glaze layer is selected from inorganic glaze layers.

[0023] By selecting a glaze layer that meets a specific thermal expansion coefficient, thickness and porosity, the relationship between the thermal expansion coefficients of the glaze layer and the porous ceramic matrix can be further regulated, so that the glaze layer and the porous ceramic matrix are compatible, which is beneficial to further improve the resistance to cold and heat shock. In addition, the glaze layer is controlled to have a low water absorption rate, which is beneficial to reduce the risk of water seepage and improve the easy cleaning and anti-pollution performance of cooking utensils.

[0024] In one embodiment, the porous ceramic matrix is ​​selected from terracotta-purple clay ceramic matrix, kaolin ceramic or cordierite ceramic.

[0025] A method for preparing the cooking vessel as described above comprises the following steps:

[0026] providing a porous ceramic substrate;

[0027] Glazing and sintering the porous ceramic substrate to obtain a pre-treated substrate, so that the inner surface and outer side wall of the pre-treated substrate have a glaze layer;

[0028] The pretreated substrate is heat-treated in a reaction atmosphere containing a carbon source to obtain the cooking vessel, wherein the concentration of the carbon source in the reaction atmosphere is 5wt%-10wt%.

[0029] The preparation method described in the present invention forms a glaze layer on the inner surface and outer side wall of the porous ceramic substrate, and then performs heat treatment in a reaction atmosphere containing a specific concentration of a carbon source, so that the carbon source is decomposed and deposited on the bottom of the exposed outer surface of the porous ceramic substrate and penetrates into its corresponding internal area. Since the inner surface and the outer side wall have the glaze layer, carbon atoms cannot penetrate the glaze layer and deposit into the macroscopic and microscopic pores of the porous ceramic substrate, thereby forming a unique structure with a glaze layer and a regionally distributed carbon film on the surface, and a carbon-containing area with selectively gradient distributed carbon inside.

[0030] In one embodiment, the step of glazing and sintering the porous ceramic substrate includes: glazing the inner surface and outer side wall of the porous ceramic substrate and then sintering, or glazing the entire porous ceramic substrate and removing the bottom glaze layer after sintering.

[0031] In one embodiment, the heat treatment satisfies at least one of the following conditions:

[0032] (1) The carbon source is selected from at least one of alkanes, alkenes, alkyl acids or alkyl alcohols;

[0033] (2) The reaction atmosphere further includes at least one of an inert gas and a reducing gas;

[0034] (3) The heat treatment temperature is 700°C-1100°C and the time is 12h-24h.

[0035] By regulating the carbon source, reaction atmosphere, temperature and time of heat treatment, the penetration of carbon atoms is facilitated and a good carbon content distribution effect is achieved.

[0036] In one embodiment, the heat treatment comprises the following steps:

[0037] The pretreated substrate is subjected to a heat treatment in a reaction atmosphere containing a carbon source;

[0038] After completion, a secondary heat treatment is continued in a reaction atmosphere containing a carbon source to obtain the cooking vessel;

[0039] Wherein, the concentration of the carbon source in the reaction atmosphere in the primary heat treatment is less than the concentration of the carbon source in the reaction atmosphere in the secondary heat treatment, and the temperature of the primary heat treatment is less than or equal to the temperature of the secondary heat treatment.

[0040] The heat treatment is divided into two gradient heat treatments, wherein, in the first heat treatment stage, carbon atoms formed by the decomposition of the carbon source begin to enter the surface and internal pores of the porous ceramic matrix and begin to form a carbon film; in the second heat treatment stage, carbon atoms continue to penetrate into the interior of the porous ceramic matrix, increasing the thickness and concentration of carburization, and carbon reacts with ferric oxide in the porous ceramic matrix to form ferric oxide, so that the porous ceramic matrix containing red ferric oxide is transformed into a heat conductor containing black ferric oxide, thereby enhancing the heat conduction and heat radiation capabilities of the cooking vessel, which is beneficial to improving the heating effect.

[0041] In one embodiment, the heat treatment satisfies at least one of the following conditions:

[0042] (1) The concentration of the carbon source in the reaction atmosphere during the primary heat treatment is 5 wt% to 7 wt%;

[0043] (2) The concentration of the carbon source in the reaction atmosphere during the secondary heat treatment is 8 wt% to 10 wt%;

[0044] (3) The temperature of the primary heat treatment is 700° C.-800° C., and the time is 1 h-5 h;

[0045] (4) The temperature of the secondary heat treatment is 800°C-1100°C, and the time is 1h-10h.

[0046] By regulating the preparation conditions of the heat treatment, it is beneficial to further regulate the carbon content and the distribution of carbon materials in the cooking vessel, thereby further improving the thermal conductivity and resistance to cold and heat shock of the cooking vessel.

[0047] In one embodiment, before the heat treatment, it also includes: preheating the pretreated substrate at a first temperature in a protective atmosphere, and then introducing a reaction atmosphere containing a carbon source at a second temperature, wherein the first temperature is less than or equal to the second temperature.

[0048] Through preheat treatment, the porous ceramic matrix can be expanded and the pores can be enlarged, which is more conducive to the penetration of carbon atoms. Then, by controlling the temperature, the introduced carbon source can be decomposed to produce carbon atoms, which promotes the penetration of carbon atoms into the porous ceramic matrix during subsequent heat treatment.

[0049] In one embodiment, the first temperature is 400°C-500°C, and / or the second temperature is 400°C-700°C.

[0050] By regulating the gradient temperature conditions twice during the heat treatment, it is more conducive to the penetration of carbon atoms and a good carbon content distribution effect can be achieved.

[0051] In one embodiment, before the preheat treatment, a catalyst is attached to the surface of the pretreated substrate, and the catalyst is selected from iron and / or nickel.

[0052] The catalyst is beneficial to accelerate the decomposition and deposition of the carbon source, thereby increasing the carburizing rate and depth. DETAILED DESCRIPTION

[0053] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific implementation methods or embodiments and are not intended to limit the present invention.

[0055] The invention provides a cooking vessel for a cooking utensil, comprising a cooking container provided with a cooking cavity, wherein the cooking container comprises a porous ceramic matrix, a glaze layer and a carbon film.

[0056] The absolute value of the difference between the thermal expansion coefficient of the glaze layer and the thermal expansion coefficient of the porous ceramic matrix is ​​less than or equal to 3×10 -6 / ℃.

[0057] The carbon film is attached to the bottom of the outer surface of the porous ceramic substrate and penetrates inward to form a carbon-containing zone. The thickness of the porous ceramic substrate is denoted as H. In the carbon-containing zone, the carbon content of the outer surface of the porous ceramic substrate is greater than or equal to 10wt%, the carbon content at H / 2 is greater than or equal to 3wt%, and the carbon content of the carbon-containing zone decreases from the outer surface of the porous ceramic substrate to the inner surface.

[0058] In the cooking vessel of the present invention, the surface of the porous ceramic substrate has a glaze layer and a regionally distributed carbon film, and the interior has a carbon-containing area with selectively gradient distributed carbon, and the glaze layer and the porous ceramic substrate satisfy a specific thermal expansion coefficient relationship. This special structure has many performance advantages:

[0059] First, the carbon material with gradient distribution in the carbon-containing zone not only fills the pores and defects in the porous ceramic matrix, thereby reducing the thermal resistance in the heat transfer process, but also forms a partial carbide phase in the porous ceramic matrix, which is beneficial to improve thermal conductivity. In addition, carbon atoms can also replace other atoms in the ceramic crystal structure, thereby changing the crystal structure, which is beneficial to further improve the thermal conductivity effect, thereby making the thermal conductivity coefficient of the cooking container reach 5W / (m·K)-10W / (m·K).

[0060] Second, it can ensure that the cooking utensils still have good thermal insulation and heat storage performance on the basis of greatly improving the thermal conductivity, thereby improving the overall energy efficiency utilization rate.

[0061] Third, the glaze layer and carbon film on the surface are beneficial to enhancing the interfacial bonding and stability of ceramic materials, alleviating the generation and propagation of thermal stress and thermal shock, and the carbon film is also beneficial to the uniform transfer of heat, which can avoid the generation of large temperature gradients and reduce the thermal stress caused by thermal shock, thereby reducing the risk of crack formation and rupture. It is especially suitable for improving the thermal shock resistance in ceramic matrices that do not contain spodumene.

[0062] In addition, the cooking vessel of the present invention not only has the above-mentioned performance advantages, but also overcomes the practical application problems of traditional carbon-based cooking vessels such as blackening and unsightly appearance.

[0063] In one embodiment, the absolute value of the difference between the thermal expansion coefficient of the glaze layer and the thermal expansion coefficient of the porous ceramic substrate is preferably less than or equal to 2×10 -6 / ℃.

[0064] In one embodiment, the thickness of the carbon film is 1 μm-20 μm. Precisely controlling the thickness of the carbon film is beneficial to further improve thermal conductivity and resistance to thermal shock.

[0065] In one embodiment, the cooking container satisfies at least one of the following conditions:

[0066] (1) The carbon content in the range of thickness H / 4 extending from the outer surface of the porous ceramic substrate to the inner surface thereof is 5wt%-13wt%;

[0067] (2) the carbon content in the range of H / 2 extending from the thickness of H / 4 toward the outer surface of the porous ceramic substrate is 3wt%-5wt%;

[0068] (3) The carbon content in the cooking container is 5wt%-10wt%.

[0069] By regulating the specific distribution of the carbon content in the cooking container, it is helpful to further improve the thermal conductivity.

[0070] In one embodiment, the glaze layer satisfies at least one of the following conditions:

[0071] (1) The thermal expansion coefficient of the glaze layer is 2×10 -4 / ℃-7×10 -4 / ℃;

[0072] (2) The thickness of the glaze layer is 20 μm-500 μm;

[0073] (3) The porosity of the glaze layer is less than 1%;

[0074] (4) The glaze layer is selected from an inorganic glaze layer, preferably a ceramic glaze layer, a glass glaze layer or an enamel glaze layer.

[0075] By selecting a glaze layer that meets a specific thermal expansion coefficient, thickness and porosity, the relationship between the thermal expansion coefficients of the glaze layer and the porous ceramic matrix can be further regulated, so that the glaze layer and the porous ceramic matrix are compatible, which is beneficial to further improve the resistance to cold and heat shock. In addition, the glaze layer is controlled to have a low water absorption rate, which is beneficial to reduce the risk of water seepage and improve the easy cleaning and anti-pollution performance of cooking utensils.

[0076] In one embodiment, the thermal expansion coefficient of the porous ceramic matrix is ​​preferably 3×10 -4 / ℃-6×10 -4 / ℃, the porous ceramic matrix is ​​selected from terracotta-purple sand ceramic matrix, kaolin ceramic or cordierite ceramic.

[0077] Therefore, using the cooking vessel of the present invention in cooking utensils can not only achieve excellent heating and heat preservation effects, but also improve the heat resistance level of the cooking vessel, avoid the risks of porcelain collapse and cracking in the cooking vessel in a hot and cold alternating environment, and meet the safety and health requirements of cooking utensils.

[0078] The present invention also provides a method for preparing the cooking vessel as described above, comprising the following steps:

[0079] S1, providing a porous ceramic substrate;

[0080] S2, glazing and sintering the porous ceramic substrate to obtain a pre-treated substrate, so that the inner surface and outer side wall of the pre-treated substrate have a glaze layer;

[0081] S3, heat-treating the pretreated substrate in a reaction atmosphere containing a carbon source to obtain the cooking vessel, wherein the concentration of the carbon source in the reaction atmosphere is 5wt%-10wt%.

[0082] In step S1, the water absorption rate of the porous ceramic matrix is ​​preferably below 25%, including but not limited to a porous oxide ceramic matrix or a porous silicate ceramic matrix, preferably a porous oxide ceramic matrix. By selecting a porous ceramic matrix with a specific component and water absorption rate, it is more conducive to regulating the carbon content and its distribution in the cooking container, thereby further improving the thermal conductivity and resistance to cold and heat shock of the cooking container, while maintaining good thermal insulation and heat storage performance.

[0083] Specifically, the main components of the porous ceramic matrix include but are not limited to at least one of Al2O3, SiO2, Fe2O3, CaO, MgO, K2O, Na2O, and TiO2.

[0084] Among them, when the content of Li2O in the porous ceramic matrix is ​​less than 0.1%, it can not only significantly reduce the cost of the cooking container, but also has the effect of improving thermal stability.

[0085] It should be noted that the existing conventional porous ceramic substrate can be used, or it can be prepared by itself according to conventional processes, including mud embryo molding, surface drying, biscuit firing, high-temperature sintering and other processes, and the present invention does not limit this.

[0086] In step S2 and step S3, a glaze layer is formed on the inner surface and outer wall of the porous ceramic substrate, and then heat treatment is performed in a reaction atmosphere containing a specific concentration of a carbon source, so that the carbon source is decomposed and deposited on the bottom of the exposed outer surface of the porous ceramic substrate and penetrates into the corresponding internal area. Since the inner surface and the outer wall have the glaze layer, carbon atoms cannot penetrate the glaze layer and deposit into the macroscopic and microscopic pores of the porous ceramic substrate, thereby forming a unique structure with a glaze layer and a regionally distributed carbon film on the surface, and a carbon-containing area with selectively gradient distributed carbon inside.

[0087] In one embodiment, the step of glazing and sintering the porous ceramic substrate includes: glazing the inner surface and outer side wall of the porous ceramic substrate and then sintering, or glazing the entire porous ceramic substrate and removing the bottom glaze layer after sintering.

[0088] Specifically, the glazing methods include but are not limited to dipping, spraying, brushing, etc. It is understandable that the glaze sintering processes of different systems are different, for example, the sintering temperature of high-temperature ceramic glaze is about 1200°C, the sintering temperature of glass glaze is 900-1100°C, and the sintering temperature of enamel glaze is 700-900°C.

[0089] In one embodiment, the heat treatment satisfies at least one of the following conditions:

[0090] (1) The carbon source is selected from at least one of alkanes, alkenes, alkyl acids or alkyl alcohols;

[0091] (2) The reaction atmosphere further includes at least one of an inert gas and a reducing gas;

[0092] (3) The heat treatment temperature is 700°C-1100°C and the time is 12h-24h.

[0093] By regulating the carbon source, reaction atmosphere, temperature and time of heat treatment, the penetration of carbon atoms is facilitated and a good carbon content distribution effect is achieved.

[0094] Specifically, the alkane includes but is not limited to methane or ethane; the olefin includes but is not limited to ethylene or propylene; the alkyl acid includes but is not limited to acetic acid or propionic acid; the alkyl alcohol includes but is not limited to methanol or ethanol; the inert gas includes but is not limited to argon, nitrogen or helium; the reducing gas includes but is not limited to hydrogen or carbon monoxide.

[0095] It should be noted that the heat treatment may be performed using existing technical means, such as chemical vapor infiltration (CVI), which is not limited in the present invention.

[0096] In one embodiment, the heat treatment comprises the following steps:

[0097] The pretreated substrate is subjected to a heat treatment in a reaction atmosphere containing a carbon source;

[0098] After completion, a secondary heat treatment is continued in a reaction atmosphere containing a carbon source to obtain the cooking vessel;

[0099] Wherein, the concentration of the carbon source in the reaction atmosphere in the primary heat treatment is less than the concentration of the carbon source in the reaction atmosphere in the secondary heat treatment, and the temperature of the primary heat treatment is less than or equal to the temperature of the secondary heat treatment.

[0100] The heat treatment is divided into two gradient heat treatments, wherein, in the first heat treatment stage, carbon atoms formed by the decomposition of the carbon source begin to enter the surface and internal pores of the porous ceramic matrix and begin to form a carbon film; in the second heat treatment stage, carbon atoms continue to penetrate into the interior of the porous ceramic matrix, increasing the thickness and concentration of carburization, and carbon reacts with ferric oxide in the porous ceramic matrix to form ferric oxide, so that the porous ceramic matrix containing red ferric oxide is transformed into a heat conductor containing black ferric oxide, thereby enhancing the heat conduction and heat radiation capabilities of the cooking vessel, which is beneficial to improving the heating effect.

[0101] In one embodiment, the heat treatment satisfies at least one of the following conditions:

[0102] (1) The concentration of the carbon source in the reaction atmosphere during the primary heat treatment is 5 wt% to 7 wt%;

[0103] (2) The concentration of the carbon source in the reaction atmosphere during the secondary heat treatment is 8 wt% to 10 wt%;

[0104] (3) The temperature of the primary heat treatment is 700° C.-800° C., and the time is 1 h-5 h;

[0105] (4) The temperature of the secondary heat treatment is 800°C-1100°C, and the time is 1h-10h.

[0106] More preferably, the heat treatment satisfies the preparation conditions of the above-mentioned primary heat treatment and secondary heat treatment at the same time, which is conducive to further regulating the carbon content and carbon material distribution in the cooking vessel, thereby further improving the thermal conductivity and thermal shock resistance of the cooking vessel.

[0107] In one embodiment, before the heat treatment, the method further includes: preheating the pretreated substrate at a first temperature in a protective atmosphere, and then introducing a reaction atmosphere containing a carbon source at a second temperature, wherein the first temperature is less than or equal to the second temperature.

[0108] Through preheat treatment, the porous ceramic matrix can be expanded and the pores can be enlarged, which is more conducive to the penetration of carbon atoms. Then, by controlling the temperature, the introduced carbon source can be decomposed to produce carbon atoms, which promotes the penetration of carbon atoms into the porous ceramic matrix during subsequent heat treatment.

[0109] Specifically, during the preheat treatment, it is preferred to introduce an inert gas to facilitate the removal of air from the reaction atmosphere.

[0110] Preferably, the first temperature is 400°C-500°C, and / or the second temperature is 400°C-700°C.

[0111] More preferably, the first temperature is preferably 400°C-500°C, and the second temperature is preferably 400°C-700°C.

[0112] By regulating the gradient temperature conditions twice during the heat treatment, it is more conducive to the penetration of carbon atoms and a good carbon content distribution effect can be achieved.

[0113] In one embodiment, before the preheat treatment, a catalyst is attached to the surface of the pretreated substrate, which is beneficial to accelerate the decomposition and deposition of the carbon source, thereby increasing the carburizing rate and depth.

[0114] Preferably, the catalyst is selected from iron and / or nickel, utilizing the high chemical reactivity and adsorption capacity of the iron and / or nickel metal surfaces. The metal surfaces can also provide reaction sites, which are conducive to the adsorption of carbon source gas and promote the decomposition and deposition of the carbon source.

[0115] In one embodiment, after the heat treatment, the cooking vessel is preferably cooled to room temperature by slow air cooling, and the supply of carbon source is gradually stopped to avoid problems such as ceramic cracking caused by thermal stress.

[0116] In one embodiment, the cooking container is preferably cleaned with a solvent such as deionized water, acetic acid or sodium hydroxide to remove the catalyst remaining on the surface.

[0117] The present invention also provides a cooking utensil, including the cooking vessel as described above, such as an electric stew pot, an electric rice cooker, an electric heating cup and the like.

[0118] The cooking vessel and the preparation method thereof will be further described below by the following specific examples. However, those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are followed. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0119] Example 1

[0120] A red pottery-purple sand ceramic substrate with a thickness of 6 mm and a volume of 5 L (wherein Li2O is about 0.01%) was selected, and was washed with deionized water and dried to remove grease, dust and other impurities on the surface.

[0121] A masking fixture was used to mask and protect the bottom of the outer surface of the terracotta-purple clay ceramic substrate, and then a spraying process was used to glaze the inner surface and outer side wall of the terracotta-purple clay ceramic substrate. After surface drying and baking, it was sintered at 1100°C for 8 hours to form a 100μm thick ceramic glaze layer on the inner surface and outer side wall of the terracotta-purple clay ceramic substrate to obtain a pretreated substrate.

[0122] The pretreated substrate is placed in a heat treatment furnace, nitrogen is introduced and the temperature is gradually preheated to 200°C for 2 hours, then the temperature is raised to 700°C, and methane is introduced into the nitrogen at the same time, so that the concentration of methane in the mixed gas is about 5wt%, and after 1 hour of heat preservation, the temperature is further raised to 800°C, so that the concentration of methane in the mixed gas is about 8wt%, and the temperature is maintained for 1 hour. After completion, it is slowly cooled to room temperature and washed to obtain a cooking vessel.

[0123] Example 2

[0124] A red pottery-purple sand ceramic substrate with a thickness of 6 mm and a volume of 5 L (wherein Li2O is about 0.05%) was selected, and was washed with deionized water and dried to remove grease, dust and other impurities on the surface.

[0125] A masking fixture was used to mask and protect the bottom of the outer surface of the terracotta-purple clay ceramic substrate, and then a spraying process was used to glaze the inner surface and outer side wall of the terracotta-purple clay ceramic substrate. After surface drying and baking, it was sintered at 1150°C for 8 hours to form a 200μm thick ceramic glaze layer on the inner surface and outer side wall of the terracotta-purple clay ceramic substrate to obtain a pretreated substrate.

[0126] The pretreated substrate was placed in a heat treatment furnace, nitrogen was introduced and the temperature was gradually preheated to 200°C for 2 hours, then the temperature was raised to 730°C, and methane was introduced into the nitrogen at the same time, so that the concentration of methane in the mixed gas was about 5.8wt%, and after 2 hours of heat preservation, the temperature was further raised to 900°C, so that the concentration of methane in the mixed gas was about 8.9wt%, and the temperature was maintained for 3 hours. After completion, it was slowly cooled to room temperature and washed to obtain a cooking vessel.

[0127] Example 3

[0128] A red pottery-purple sand ceramic substrate with a thickness of 6 mm and a volume of 5 L (wherein Li2O is about 0.06%) was selected, and was washed with deionized water and dried to remove grease, dust and other impurities on the surface.

[0129] A masking fixture was used to mask and protect the bottom of the outer surface of the terracotta-purple clay ceramic substrate, and then the inner surface and outer side wall of the terracotta-purple clay ceramic substrate were glazed by dipping. After surface drying and baking, it was sintered at 1100°C for 8 hours to form a 300μm thick ceramic glaze layer on the inner surface and outer side wall of the terracotta-purple clay ceramic substrate to obtain a pretreated substrate.

[0130] The pretreated substrate was placed in a heat treatment furnace, nitrogen was introduced and the temperature was gradually preheated to 200°C for 2 hours, then the temperature was raised to 780°C, and methane was introduced into the nitrogen at the same time, so that the concentration of methane in the mixed gas was about 6.5wt%, and after 3.5 hours of heat preservation, the temperature was further raised to 1000°C, so that the concentration of methane in the mixed gas was about 9wt%, and the temperature was maintained for 6 hours. After completion, the cooking vessel was slowly cooled to room temperature and cleaned to obtain the cooking vessel.

[0131] Example 4

[0132] A red pottery-purple sand ceramic substrate with a thickness of 6 mm and a volume of 5 L (wherein Li2O is about 0.08%) was selected, and was washed with deionized water and dried to remove grease, dust and other impurities on the surface.

[0133] A masking fixture was used to mask and protect the bottom of the outer surface of the terracotta-purple clay ceramic substrate, and then the inner surface and outer side wall of the terracotta-purple clay ceramic substrate were glazed by dipping. After surface drying and baking, it was sintered at 1100°C for 8 hours to form a 500μm thick ceramic glaze layer on the inner surface and outer side wall of the terracotta-purple clay ceramic substrate to obtain a pretreated substrate.

[0134] The pretreated substrate is placed in a heat treatment furnace, nitrogen is introduced and the temperature is gradually preheated to 200°C for 2 hours, then the temperature is raised to 800°C, and methane is introduced into the nitrogen at the same time, so that the concentration of methane in the mixed gas is about 7wt%, and after 1 hour of heat preservation, the temperature is further raised to 1100°C, so that the concentration of methane in the mixed gas is about 10wt%, and the temperature is maintained for 10 hours. After completion, it is slowly cooled to room temperature and washed to obtain a cooking vessel.

[0135] Example 5

[0136] A cordierite ceramic substrate with a thickness of 6 mm and a volume of 5 L (wherein Li2O is about 0.8%) was selected, and was cleaned with deionized water and dried to remove grease, dust and other impurities on the surface.

[0137] A masking fixture was used to mask and protect the bottom of the outer surface of the terracotta-purple clay ceramic substrate, and then a spraying process was used to glaze the inner surface and outer side wall of the terracotta-purple clay ceramic substrate. After surface drying and baking, it was sintered at 1200°C for 8 hours to form a 500μm thick enamel glaze layer on the inner surface and outer side wall of the terracotta-purple clay ceramic substrate to obtain a pretreated substrate.

[0138] The pretreated substrate is placed in a heat treatment furnace, nitrogen is introduced and the temperature is gradually preheated to 200°C for 2 hours, then the temperature is raised to 800°C, and methane is introduced into the nitrogen at the same time, so that the concentration of methane in the mixed gas is about 7wt%, and after 5 hours of heat preservation, the temperature is further raised to 1100°C, so that the concentration of methane in the mixed gas is about 10wt%, and the temperature is maintained for 10 hours. After completion, it is slowly cooled to room temperature and washed to obtain a cooking vessel.

[0139] Comparative Example 1

[0140] The same red pottery-purple sand ceramic substrate as in Example 1 was directly used as a cooking vessel.

[0141] Comparative Example 2

[0142] The difference between Comparative Example 2 and Example 1 is that only the inner surface of the porous ceramic substrate is glazed, and the outer surface of the cooking vessel is completely carburized.

[0143] Comparative Example 3

[0144] The difference between Comparative Example 3 and Example 1 is that the concentration of the carbon source in the reaction atmosphere in both the primary heat treatment and the secondary heat treatment is 2 wt %.

[0145] Comparative Example 4

[0146] The difference between Comparative Example 4 and Example 1 is that the concentration of the carbon source in the reaction atmosphere in both the primary heat treatment and the secondary heat treatment is 4.5 wt %.

[0147] Comparative Example 5

[0148] The difference between Comparative Example 5 and Example 1 is that the thermal expansion coefficient of the surface of the porous ceramic substrate is 2×10 -6 / ℃ glaze layer.

[0149] Examples 1-6 and comparative examples 2-5 were tested, and the results are shown in Tables 1 and 2. In Table 2, the thickness of the cooking container is H, the carbon content at the bottom of the groove close to the surface of the carbon film substrate is X, the carbon content at the bottom of the groove close to the surface of the carbon film substrate extending H / 4 in the direction of the substrate is h1, the carbon content at H / 2 extending H / 4 in the direction of the groove is h2, and the carbon content at H / 2 is Y, then the average carbon content = (X+h1+h2+Y) / 4.

[0150] Table 1

[0151]

[0152] Table 2

[0153]

[0154] The cooking utensils prepared in Examples 1-6 and Comparative Examples 1-5 were subjected to performance tests, and the results are shown in Table 3.

[0155] Test method: Place the cooking vessel on the electric stew pot for a 600W heating test. Add tap water with an initial water temperature of 24°C and a water volume of 2.1L. The electric stew pot is heated by a bottom heating plate. Under the same conditions, test the time it takes for the boiling water temperature to reach 99°C, and the insulation temperature after power off for two hours after 99°C. The cold and heat shock resistance adopts GB-T3298-2022.

[0156] Table 3

[0157]

[0158]

[0159] According to Table 3, by comparing Example 1 with Comparative Example 1, it can be seen that the cooking vessel provided by the present invention has a faster boiling efficiency, greatly improves the thermal conductivity, and has no significant reduction in the thermal insulation effect. The heat resistance level is close to the level of spodumene ceramics (>400°C), which can fully meet the use conditions on electrical appliances. Although Comparative Example 2 has a better boiling efficiency, it has a poor appearance, poor safety and durability due to the carburized layer on the outer surface, and cannot be used for dishwasher cleaning, which limits the scope of application; Comparative Example 5 has cracks in the glaze layer during the high-temperature sintering process, and further cracks in the glaze layer during the high-temperature carburizing process, resulting in failure of thermal conductivity, thermal insulation and heat resistance.

[0160] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0161] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A cooking vessel for cooking utensils, the cooking vessel comprising a cooking container provided with a cooking cavity, characterized in that: The cooking container comprises a porous ceramic substrate, a glaze layer and a carbon film; The glaze layer is attached to the inner surface and the outer wall of the porous ceramic substrate, and the absolute value of the difference between the thermal expansion coefficient of the glaze layer and the thermal expansion coefficient of the porous ceramic substrate is less than or equal to 3×10 -6 / ℃; The carbon film is attached to the bottom of the outer surface of the porous ceramic substrate and penetrates inward to form a carbon-containing zone. The thickness of the porous ceramic substrate is denoted as H. In the carbon-containing zone, the carbon content of the outer surface of the porous ceramic substrate is greater than or equal to 10wt%, the carbon content at H / 2 is greater than or equal to 3wt%, and the carbon content of the carbon-containing zone decreases from the outer surface of the porous ceramic substrate to the inner surface.

2. The cooking vessel according to claim 1, characterized in that: The thickness of the carbon film is 1 μm-20 μm.

3. The cooking vessel according to claim 1, characterized in that: The cooking container satisfies at least one of the following conditions: (1) The carbon content in the range of thickness H / 4 extending from the outer surface of the porous ceramic substrate to the inner surface thereof is 5wt%-13wt%; (2) the carbon content in the range of H / 2 extending from the thickness of H / 4 toward the outer surface of the porous ceramic substrate is 3wt%-5wt%; (3) The carbon content in the cooking container is 5wt%-10wt%.

4. The cooking vessel according to claim 1, characterized in that: The glaze layer satisfies at least one of the following conditions: (1) The thermal expansion coefficient of the glaze layer is 2×10 -4 / ℃-7×10 -4 / ℃; (2) The thickness of the glaze layer is 20 μm-500 μm; (3) The porosity of the glaze layer is less than 1%; (4) The glaze layer is selected from inorganic glaze layers.

5. The cooking vessel according to claim 1, characterized in that: The porous ceramic matrix is ​​selected from terracotta-purple sand ceramic matrix, kaolin ceramic or cordierite ceramic.

6. A method for preparing a cooking vessel according to any one of claims 1 to 5, characterized in that: The steps include: providing a porous ceramic substrate; Glazing and sintering the porous ceramic substrate to obtain a pre-treated substrate, so that the inner surface and outer side wall of the pre-treated substrate have a glaze layer; The pretreated substrate is heat-treated in a reaction atmosphere containing a carbon source to obtain the cooking vessel, wherein the concentration of the carbon source in the reaction atmosphere is 5wt%-10wt%.

7. The method for preparing a cooking vessel according to claim 6, characterized in that: The steps of glazing and sintering the porous ceramic substrate include: glazing the inner surface and outer side wall of the porous ceramic substrate and then sintering, or glazing the entire porous ceramic substrate and removing the bottom glaze layer after sintering.

8. The method for preparing a cooking vessel according to claim 6, characterized in that: The heat treatment satisfies at least one of the following conditions: (1) The carbon source is selected from at least one of alkanes, alkenes, alkyl acids or alkyl alcohols; (2) The reaction atmosphere further includes at least one of an inert gas and a reducing gas; (3) The heat treatment temperature is 700°C-1100°C and the time is 12h-24h.

9. The method for preparing a cooking vessel according to claim 6 or 8, characterized in that: The heat treatment comprises the following steps: The pretreated substrate is subjected to a heat treatment in a reaction atmosphere containing a carbon source; After completion, a secondary heat treatment is continued in a reaction atmosphere containing a carbon source to obtain the cooking vessel; Wherein, the concentration of the carbon source in the reaction atmosphere in the primary heat treatment is less than the concentration of the carbon source in the reaction atmosphere in the secondary heat treatment, and the temperature of the primary heat treatment is less than or equal to the temperature of the secondary heat treatment.

10. The method for preparing a cooking vessel according to claim 9, characterized in that: The heat treatment satisfies at least one of the following conditions: (1) The concentration of the carbon source in the reaction atmosphere during the primary heat treatment is 5 wt% to 7 wt%; (2) The concentration of the carbon source in the reaction atmosphere during the secondary heat treatment is 8 wt% to 10 wt%; (3) The temperature of the primary heat treatment is 700° C.-800° C., and the time is 1 h-5 h; (4) The temperature of the secondary heat treatment is 800°C-1100°C, and the time is 1h-10h.

11. The method for preparing a cooking vessel according to claim 6, characterized in that: Before the heat treatment, the method further includes: preheating the pretreated substrate at a first temperature in a protective atmosphere, and then introducing a reaction atmosphere containing a carbon source at a second temperature, wherein the first temperature is less than or equal to the second temperature.

12. The method for preparing a cooking vessel according to claim 11, characterized in that: The first temperature is 400°C-500°C, and / or the second temperature is 400°C-700°C.

13. The method for preparing a cooking vessel according to claim 12, characterized in that: Before the preheat treatment, a catalyst is attached to the surface of the pretreated substrate, and the catalyst is selected from iron and / or nickel.

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