Method for producing ceramic material based on steatite

Abstract

FIELD: insulating materials.SUBSTANCE: invention relates to the technology of insulating ceramic materials, in particular to the development of new compositions of steatite ceramics capable of improving the performance characteristics of insulation in electronics and electrical engineering, for example in the production of sealed structures for various devices: variable capacitor axes, coil housings, resistor frames, lamp panels, as well as in support plates and insulating rings. A method for producing a ceramic material based on steatite is proposed, including solid-phase synthesis, consisting of the following: a batch is made up, including magnesium oxide, silicon oxide, barium carbonate, aluminium oxide and boric acid, whereas the raw materials used are not lower than the chemically pure grade, based on the calculation, taking into account the loss on ignition per 1 kg of mass: magnesium oxide 337.33 g, silicon oxide 630.00 g, barium carbonate 8.60 g, aluminium oxide 25.39 g, boric acid 51.10 g. The components of the batch are ground to a specific surface area of no more than 5500± 100 cm2 / g, mixed in a roller mill for 16 hours with the addition of oleic acid at a rate of 3 wt.%. The prepared mixture is rubbed through a sieve and subjected to briquetting. The briquettes are heat treated at 1290 °C with a holding time of 2 hours, and cooling occurs together with the furnace, obtaining a synthesized material, which is a mixture of steatite, quartz and cristobalite phases. The synthesized material is ground, the powder is dried and a slip is prepared, the blanks are formed using the hot slip casting method, the binder is removed and sintered at a temperature of 1350 °C.EFFECT: improving the electrophysical properties and increasing the mechanical strength of the material.4 cl, 1 dwg, 1 tbl

Description

[0001] Field of technology to which the invention relates

[0002] The invention relates to a chemical technology for producing a ceramic material based on steatite by a solid-phase synthesis method without the use of natural raw materials, but using raw materials with a low impurity content of a purity not lower than the grade / classification of chemically pure (chemically pure).

[0003] The invention also relates to the technology of insulating ceramic materials, specifically the development of new compounds based on steatite ceramics capable of improving the performance characteristics of insulation, including in electronics and electrical engineering. The proposed invention is used to manufacture sealed structures for various devices: variable capacitor axes, coil housings, resistor frames, lamp bases, and other components such as support plates and insulating rings.

[0004] State of the art

[0005] The authors of the invention have not identified any patented technical solutions for methods of producing steatite materials over the past 10 years.

[0006] Methods for producing ceramic materials based on steatite are known and are described in textbooks and reference materials.

[0007] In educational and reference publications on the production of ceramic materials, methods for obtaining ceramic materials based on steatite (clinoenstatite) are indicated:

[0008] - Publication of the D.I. Mendeleyev University of Chemical Technology of Russia "Answers on Technical Ceramics"

[0009] https: / / studfile.net / preview / 9465332 / :

[0010] Chapter 10. Soapstone ceramics: types, technology, and areas of application. Soapstone ceramics are divided into high-voltage and high-frequency according to their purpose and properties, and consist of plastic, low-plastic, and non-plastic masses according to their mass composition and manufacturing technology. High-voltage products made from plastic masses are manufactured using a technology similar to that used for high-voltage electroporcelain. During mass production, a portion of the talc (50-60%) is fired at 1250-1350°C. Talc firing is necessary to improve molding properties by eliminating delamination due to the "fat" content of the talc; 15-25% of talc is added in unfired form. To impart plastic properties to the mass, 7-12% clay and 3-5% bentonite are added. Blanks of the mass, drawn through vacuum presses, are turned on lathes, formed in plaster molds, etc. Large-sized parts are manufactured using this method.

[0011] Low-plasticity masses containing 2-5% clay are molded by pressing, adding 4-6% organic binder (oleic acid, etc.). This molding method can include up to 20-40% unfired talc. Pressing is primarily used to manufacture electrical components. Firing is at 1300°C.

[0012] High-frequency products are made from non-plastic masses (without added clay) containing 85-90% calcined talc using the hot casting method. The casting slip is obtained from finely ground sintered paraffin-bonded clay, consisting of 9-12% paraffin and 0.5% oleic acid. The products are fired at 1200°C.

[0013] - Ceramic technology for materials of the electronic industry: textbook. In 2 parts. Part 1 / A.S. Tolkacheva, I.A. Pavlova. - Ekaterinburg: Ural University Publishing House, 2019. - 124 p.

[0014] Chapter 1.1. Steatite (enstatite) ceramics. Steatite ceramics based on natural magnesite (silicate) raw materials, primarily talc (3MgO-4SiO⋅2H2O), and clay components. Dense varieties of talc are called steatite. Steatite (clinoenstatite) ceramics are named for the main crystalline component of this type of ceramics - magnesium metasilicate MgO⋅SiO2 - clinoenstatite. In China, Australia, and the Czech Republic, this material is called "steolite."

[0015] Advantages of soapstone ceramics:

[0016] cheap material (based on natural raw materials - fine crystalline talc);

[0017] Good dielectric properties and high mechanical strength at room and elevated temperatures and in high-frequency fields;

[0018] low abrasiveness, which significantly facilitates the operating conditions of the mold and the process of semi-dry molding of products.

[0019] Disadvantages of soapstone ceramics:

[0020] narrow sintering range (10-30°C), furnaces with silicon carbide heaters are used;

[0021] aging (degradation of dielectric properties and mechanical strength over time)".

[0022] All known methods for producing soapstone-based ceramics involve the use of a natural raw material – talc. The use of natural talc has several advantages:

[0023] - Even within a single talc deposit, the chemical composition varies depending on the depth and location of mining. And the chemical composition of different deposits can differ dramatically;

[0024] - Natural raw materials always contain unwanted impurities, which sometimes greatly affects the properties of the resulting material.

[0025] Disclosure of invention

[0026] The method for producing a ceramic material based on steatite proposed in the invention allows one to avoid the above mentioned disadvantages since it uses raw materials of a grade not lower than chemically pure.

[0027] The technical result of the claimed invention consists in the use of a different type of raw material while simultaneously increasing the operational insulating characteristics of the material, as well as improving the electrophysical properties and increasing the mechanical strength of the material.

[0028] In order to achieve the above technical result, a method for producing a ceramic material based on steatite is proposed, including solid-phase synthesis, consisting in the following: a batch is made up, including magnesium oxide, silicon oxide, barium carbonate, aluminum oxide and boric acid, while the raw materials used are not lower than the chemically pure grade, and the components of the batch are prepared taking into account losses on ignition based on 1 kg of mass: magnesium oxide - 337.33 g, silicon oxide - 630.00 g, barium carbonate - 8.60 g, aluminum oxide - 25.39 g, boric acid - 51.10 g; the components of the batch are ground to a specific surface area of ​​​​not more than 5500±100 cm2 / g, mixed in a roller mill for 16 hours, with the addition of oleic acid at the rate of 3 wt.%; the prepared batch is rubbed through a sieve, subjected to briquetting to ensure “close order”, then the briquettes are heat-treated at a temperature of 1290°C for 2 hours, and cooling occurs together with the furnace, resulting in a synthesized material that is a mixture of steatite, quartz and cristobalite phases.

[0029] Furthermore, in order to achieve the above technical result, a method is proposed for manufacturing an article from a steatite-based ceramic material, which is a mixture of steatite, quartz and cristobalite phases obtained according to the above method for producing a steatite-based ceramic material, which consists of grinding briquettes in a jaw crusher, grinding them in a ball mill to an average particle size of 10 μm, then drying the powder in a drying oven for 2 hours at a temperature of 120 ° C, preparing a slip from the resulting powder, vacuuming the prepared slip in a hot slip casting unit (HSCU) with molding of blanks, removing the temporary process binder (TPB) from the blanks by heat treatment in crucibles or capsules with a backfill volume of refractory powder, firing semi-finished products at a temperature of 1350 ° C in within 45 minutes with the production of a product from the synthesized material,A mixture of steatite, quartz, and cristobalite phases. According to the method, the powder-to-grinding-media ratio can be set at 1:4, with grinding performed in a steel drum lined internally with corundum plates at a drum rotation speed of 34 rpm. Corundum balls with a diameter of 12 mm are used as grinding media. The claimed method allows for the preparation of a slip with a 9% refractory-to-metal (RTM) concentration, and the removal of refractory-to-metal (RTM) from the workpieces by heat treatment in crucibles or a capsule containing a backfill volume of refractory powder, using the following regime:

[0030] - 1 day: heating to 70°C for 8 hours, holding for 1 hour;

[0031] - Day 2: heating to 70°C for 1 hour, subsequent heating to 100°C for 7 hours, holding for 1 hour;

[0032] - Day 3: heating to 100°C for 1 hour, subsequent heating to 200°C for 7 hours, holding for 1 hour;

[0033] - Day 4: heating to 150°C for 1 hour, subsequent heating to 300°C for 7 hours, holding for 1 hour.

[0034] Brief description of drawings

[0035] The figure shows the X-ray phase analysis (XRD) of the synthesized steatite-based ceramic material according to the present invention.

[0036] Implementation of the invention

[0037] The claimed method for producing a steatite-based ceramic material for solid-phase synthesis involves forming a batch of magnesium oxide, silicon oxide, barium carbonate, aluminum oxide, and boric acid of at least chemically pure grade. Barium is added to the batch to enhance the dielectric properties of the synthesized material, aluminum oxide to increase mechanical strength, and boric acid to accelerate the solid-phase synthesis process.

[0038] The composition of the batch, taking into account the loss on ignition, per 1 kg of mass: magnesium oxide - approximately 337.33 g, silicon oxide - approximately 630.00 g, barium carbonate - approximately 8.60 g, aluminum oxide - approximately 25.39 g, boric acid - approximately 51.10 g. Slightly larger quantities of materials were used in the preparation of the batch. These "losses" occur during heat treatment, when some components, such as carbonates and boric acid, decompose or evaporate, losing water or carbon dioxide, which leads to a decrease in their mass. Therefore, a batch mass greater than 1 kg allows for the expected loss on ignition to be taken into account in order to obtain the desired quantity of the final product.

[0039] The components of the batch are ground to a state with a specific surface area of ​​no more than 5500±100 cm 2 / g and mixed in a roller mill for approximately 16 hours. During mixing, oleic acid was added at a rate of approximately 3 wt%. The components of the batch were ground to a specific surface area of ​​no more than 5500±100 cm 2 / g, since if the batch size exceeds this value, the amount of oleic acid will need to be increased. This, in turn, can lead to the formation of new phases during the production of steatite ceramics and, consequently, changes in the physical and mechanical properties of the final product.

[0040] It is known that the surface area of ​​the oleic acid molecule is 22 square angstroms, or 22×10-16 cm 2 From this, we can calculate how many oleic acid molecules are required to occupy the surface area of ​​1 gram of steatite powder:

[0041]

[0042] Now you can calculate how many grams of oleic acid are needed to cover 1 gram of powder with a monolayer:

[0043]

[0044] where N is the number of molecules required to cover the surface area of ​​1 gram of powder with a monolayer of surfactant, M is the molar mass of oleic acid.

[0045] Thus, to cover 100 grams of powder with a monolayer, it is necessary to add 0.3 grams of oleic acid to it.

[0046] After mixing, the batch was unloaded and sieved. The prepared batch was briquetted to ensure "close order" for more complete solid-phase synthesis, which allows for a more uniform particle distribution and improves solid-phase synthesis conditions. In the context of materials science, the term "close order" or "short-range order" typically refers to an ordered structure at the microscopic particle level, which promotes optimal interactions between components and reduces the amount of disordered phases in the final product. This is crucial for achieving high physical and mechanical properties of the ceramic material, as the closest possible order in the structure promotes improved diffusion processes. This, in turn, positively impacts synthesis efficiency by ensuring a more uniform distribution of the reactants.

[0047] The prepared briquettes were heat-treated at approximately 1290°C for approximately 2 hours. Cooling occurred simultaneously with the furnace. The proposed method yields a synthesized material (powder) consisting of a mixture of steatite, quartz, and cristobalite phases.

[0048] As can be seen from the figure, the synthesized ceramic material is a mixture of steatite, quartz and cristobalite phases.

[0049] The quantitative percentage composition of the above phases of the material is presented in Table 1.

[0050]

[0051] To produce the final product, the resulting briquettes were ground in a jaw crusher and then crushed in a ball mill to an average particle size of 10 µm. The powder-to-grinding media ratio was 1:4. Grinding itself took place in a steel drum lined with corundum plates. Corundum balls with a diameter of 12 mm were used as grinding media. The drum rotation speed during grinding was 34 rpm. After grinding, the powder was sieved through a 1 mm sieve to remove the grinding media. The sieved powder was dried in an oven for 2-3 hours at a temperature of 110-130°C.

[0052] A slip with a temporary process binder (TPB) concentration of 9% by weight was prepared from the resulting powder. Preparation was carried out in a steel beaker placed in a water bath at a water temperature of 90°C. Ten percent of the powder weight (100 g) of binder was added to the steel beaker. The powder was added in 10 g portions and mixed simultaneously until a homogeneous mass (slip) was formed. The prepared slip was evacuated using a UGShL (hot slip casting unit), as otherwise, this could lead to the formation of pores and cavities within and on the surface of the product.

[0053] Slip vacuuming mode:

[0054] - Activator rotation frequency, 20-30 rpm;

[0055] - Vacuuming duration is 20-30 minutes.

[0056] The GShL (hot slip casting) unit was used to mold ceramic product blanks from slips using a thermoplastic binder using the hot slip casting method under pressure.

[0057] Technological parameters of the UGShL when forming blanks from slip based on steatite powder:

[0058] - Working temperature of slip, 74-76°C;

[0059] - Sprue temperature 74-76°C;

[0060] - Air pressure on the surface of the slip, 2-2.2 atm;

[0061] To remove the VTS from the blanks, heat treatment was carried out in crucibles or a capsule with a filling volume of G00 refractory powder, the particle size of which did not exceed 20-40 μm, according to the following regime:

[0062] - 1 day: heating to 70°C for 8 hours, holding for 1 hour;

[0063] - Day 2: heating to 70°C for 1 hour, subsequent heating to 100°C for 7 hours, holding for 1 hour;

[0064] - Day 3: heating to 100°C for 1 hour, subsequent heating to 200°C for 7 hours, holding for 1 hour;

[0065] - Day 4: heating to 150°C for 1 hour, subsequent heating to 300°C for 7 hours, holding for 1 hour.

[0066] The semi-finished products were fired at a temperature of 1300-1350°C for 30-50 minutes.

[0067] The claimed method for producing a ceramic material based on steatite is carried out as follows.

[0068] For solid-phase synthesis, a charge of magnesium oxide, silicon oxide, barium carbonate, aluminum oxide, and boric acid of at least chemically pure grade is prepared. The charge composition, taking into account losses on ignition, per 1 kg of mass: magnesium oxide - 337.33 g, silicon oxide - 630.00 g, barium carbonate - 8.60 g, aluminum oxide - 25.39 g, boric acid - 51.10 g. The charge components are ground to a specific surface area of ​​5500 cm 2 / g and mixed in a roller mill for 16 hours. Oleic acid was added during mixing at a concentration of 3 wt.%. After mixing, the mixture was removed and sieved. The prepared mixture was briquetted to ensure "close order" for more complete solid-phase synthesis. The prepared briquettes were heat-treated at 1290°C for 2 hours. Cooling occurred simultaneously with the furnace. The proposed method yields a synthesized material consisting of a mixture of 95% steatite, 2% quartz, and 3% cristobalite.

[0069] Next, if it is necessary to obtain a powder of a steatite-based ceramic material, a method for manufacturing an article of said steatite-based ceramic material is proposed as a separate embodiment of the present invention. The resulting briquettes were ground in a jaw crusher and then crushed in a ball mill to an average particle size of 10 μm. The powder:grinding media ratio was 1:4. The grinding itself took place in a steel drum lined with corundum plates. Corundum balls with a diameter of 12 mm were used as grinding media. The drum rotation speed during grinding was 34 rpm. After grinding, the powder was sifted through a sieve with a mesh size of 1 mm to remove the grinding media. The sifted powder was dried in a drying oven for 2 hours at a temperature of 120°C.

[0070] A slip with a 9% wt. BTS concentration was prepared from the resulting powder. Preparation was carried out in a steel beaker placed in a water bath at a water temperature of 90°C. A binder (10% of the powder weight, or 100 g) was added to the steel beaker. The powder was added in 10 g portions and mixed simultaneously until a homogeneous mass (slip) was formed. The prepared slip was evacuated using an ECON-UGShL unit, as otherwise, this could lead to the formation of pores and voids within and on the surface of the product.

[0071] Slip vacuuming mode:

[0072] - Activator rotation speed, 25 rpm;

[0073] - Vacuuming duration is 25 minutes.

[0074] The GShL unit was used to form ceramic product blanks from slips using a thermoplastic binder using the hot slip casting method under pressure.

[0075] Technological parameters of the UGShL when forming blanks from slip based on steatite powder:

[0076] - Working temperature of slip, 75°C;

[0077] - Sprue temperature 75°C;

[0078] - Air pressure on the surface of the slip, 1.8-2 atm;

[0079] To remove the VTS from the blanks, heat treatment was carried out in crucibles or a capsule with a filling volume of G00 refractory powder, the particle size of which did not exceed 30 μm, according to the following regime:

[0080] - 1 day: heating to 70°C for 8 hours, holding for 1 hour;

[0081] - Day 2: heating to 70°C for 1 hour, subsequent heating to 100°C for 7 hours, holding for 1 hour;

[0082] - Day 3: heating to 100°C for 1 hour, subsequent heating to 200°C for 7 hours, holding for 1 hour;

[0083] - Day 4: heating to 150°C for 1 hour, subsequent heating to 300°C for 7 hours, holding for 1 hour.

[0084] The semi-finished products were fired at a temperature of 1350°C for 45 minutes.

[0085] The result is a product made of a synthesized material, which is a mixture of steatite, quartz and cristobalite phases.

Claims

1. A method for producing a steatite-based ceramic material involving solid-phase synthesis, comprising the following: a charge comprising magnesium oxide, silicon oxide, barium carbonate, aluminum oxide, and boric acid, wherein the raw materials used are of grades not lower than chemically pure, and the charge components are prepared taking into account losses on ignition based on 1 kg of mass: magnesium oxide - 337.33 g, silicon oxide - 630.00 g, barium carbonate - 8.60 g, aluminum oxide - 25.39 g, boric acid - 51.10 g; the charge components are ground to a specific surface area of ​​no more than 5500±100 cm 2 / g, mixed in a roller mill for 16 hours with the addition of oleic acid at a rate of 3 wt.%; the prepared mixture is rubbed through a sieve, subjected to briquetting to ensure “close order”, then the briquettes are heat-treated at a temperature of 1290°C for 2 hours, and cooling occurs together with the furnace to obtain a synthesized material, which is a mixture of steatite, quartz and cristobalite phases.

2. A method for manufacturing an article from a steatite-based ceramic material, which is a mixture of steatite, quartz and cristobalite phases, obtained according to paragraph 1, consisting of grinding briquettes in a jaw crusher, crushing them in a ball mill to an average particle size of 10 μm, subsequently drying the powder in a drying oven for 2 hours at a temperature of 120°C, preparing a slip from the obtained powder, vacuuming the prepared slip in a hot slip casting unit with molding of blanks, removing a temporary process binder (TPB) from the blanks by means of heat treatment in crucibles or a capsule with a backfill volume of refractory powder, firing the semi-finished products at a temperature of 1350°C for 45 minutes to obtain an article from the synthesized material, which is a mixture of steatite, quartz and cristobalite phases.

3. The method according to paragraph 2, in which the ratio of powder:grinding media is selected to be 1:4, and the grinding is carried out in a steel drum lined on the inside with corundum plates, with a drum rotation speed of 34 rpm, and corundum balls with a diameter of 12 mm are used as grinding media.

4. The method according to paragraph 2, in which a slip with a refractory powder concentration of 9% is prepared, and the removal of the refractory powder from the blanks by means of heat treatment in crucibles or a capsule with a filling volume of refractory powder is carried out according to the following regime: - 1 day: heating to 70°C for 8 hours, holding for 1 hour; - Day 2: heating to 70°C for 1 hour, subsequent heating to 100°C for 7 hours, holding for 1 hour; - Day 3: heating to 100°C for 1 hour, subsequent heating to 200°C for 7 hours, holding for 1 hour; - Day 4: heating to 150°C for 1 hour, subsequent heating to 300°C for 7 hours, holding for 1 hour.

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