Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/20—Graphite
  • C01B32/205—Preparation
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/90—Carbides
  • C01B32/914—Carbides of single elements
  • C01B32/956—Silicon carbide
  • C01B32/963—Preparation from compounds containing silicon
  • C01B32/97—Preparation from SiO or SiO2
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
  • C04B35/56—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbides or oxycarbides
  • C04B35/565—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbides or oxycarbides based on silicon carbide
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/48—Organic compounds becoming part of a ceramic after heat treatment, e.g. carbonising phenol resins
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/65—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes
  • C04B2235/658—Atmosphere during thermal treatment
  • C04B2235/6581—Total pressure below 1 atmosphere, e.g. vacuum

Definitions

• the invention relates to a method for producing porous carbon or graphite with a homogeneous and hard structure, which is suitable for mechanical processing to produce molded parts.
• Carbon materials are usually produced by grinding coke, soot or graphite until a granulate with a desired particle size, or powder, is obtained. Since it is not possible to reshape this granulate simply by pressing it, a suitable binder, such as a thermoplastic, is added to the granulate. This mixture is then homogenized and pressed into a desired shape. The shaped body thus produced, also referred to as a green body, is finally carbonized or carbonized in a furnace under a suitable atmosphere at high temperatures. graphitized .
• a suitable binder such as a thermoplastic
• CN 113 620 272 A discloses a method for producing battery electrodes made of graphite, in which initially starch and carbon black are mechanically and uniformly mixed with one another in a predetermined ratio. The mixture is then poured into a crucible and stabilized in a muffle furnace at 200-600° C. for 3-8 hours. Finally, the mixture at 800 - 1 . Carbonized at 600 °C in a nitrogen atmosphere to produce soot-based carbon microspheres for 1-3 h, followed by cooling to room temperature.
• the invention is therefore based on the object of creating an easy-to-implement process for the cost-effective production of porous carbon or graphite with a homogeneous and hard structure from renewable raw materials, which requires mechanical post-processing for the production of any molded parts for use as structural elements, casting molds or containers and which can easily be converted into SiC molded parts.
• the slow heating up to a first temperature level preferably takes place in 5° C. steps, with a waiting time between the steps of approx. 8 hours.
• Sugar or a vegetable oil can also be added to the wheat, corn or rice starch as a binder.
• the mixture of wheat or rice starch with sugar or oil is admixed with other graphitizable materials as other foreign substances.
• High-temperature-resistant polymers carbon black, graphite dust, natural graphite, PVA (polyvinyl alcohol) adhesive, for example, come into consideration as graphitizable materials.
• natural fibers such as cotton, cellulose, bamboo, hemp, etc. can also be added.
• the mass filled into the mold/container is compressed/densified by generating a uniform compressive force acting on the mass, e.g. B. by additional loading of a plate resting on the mass by weights, or by shaking (e.g. with a vibrating plate or another vibrating device), or shaking the mold/container, or hard impulses from the side or from below act on the mass, e.g. B. by hitting against the mold / the container, so that a compact molding is formed.
• a uniform compressive force acting on the mass e.g. B. by additional loading of a plate resting on the mass by weights, or by shaking (e.g. with a vibrating plate or another vibrating device), or shaking the mold/container, or hard impulses from the side or from below act on the mass, e.g. B. by hitting against the mold / the container, so that a compact molding is formed.
• the compression/densification of the mass can also take place during the heating up by loading a weight on it.
• the heating ramp for carbonizing or graphitizing should be ⁇ 1°C/min or less, pausing ⁇ 30 to 120 minutes at each 50°C to 100°C step, allowing the material to relax while allowing gases such as Air or water vapor can diffuse out without damaging the structure.
• the concrete selection of the heating ramp and stage also depends on the pressure during this process, so that heating can be carried out more quickly overall at a higher pressure.
• the noble gases helium, neon, argon, krypton, xenon and radon can be used as protective gases.
• the carbonization or graphitization is preferably carried out at a pressure of >500 mbar.
• a mold/container made of Teflon (up to a maximum temperature of 250°C) or other suitable material can be used to be able to easily remove the moulding, alternatively it is possible to place the mold/container in front line with a cloth before filling in the mass.
• the graphite blank 5 produced according to the invention can easily be converted into SiC in a furnace at a temperature of >1,200° C. with the supply of SiO with argon as carrier gas at a pressure of 30 mbar, with a temperature of approx. 1,520° C. being preferred .
• 1a shows a mold/container filled with a mixture of wheat starch and foreign substances; 1b shows the filled container after carbonization;
• Figure 2 shows a cloth-lined container
• FIG. 3 shows a carbonized mass made from wheat starch and sugar and edible oil as a foreign substance after the first heating to 250° C.
• FIG. 5 shows the blank according to FIG. 4, finished as a shaped body, after turning from both sides (outside and inside).
• the method according to the invention initially comprises the following steps:
• the mass 2 filled into the mold/container 1 is compressed by generating a uniform compressive force acting on the mass 2, e.g. B. by additional loading of a plate lying on the mass 2 by weights, or by shaking (e.g. with a vibrating plate or another vibrating device), or shaking the mold/container, or hard impulses, which are laterally or from below on the Mass 2 act, e.g. B. by hitting against the mold / container 1, compacted so that a compact mass 2 is formed.
• a uniform compressive force acting on the mass 2 e.g. B. by additional loading of a plate lying on the mass 2 by weights, or by shaking (e.g. with a vibrating plate or another vibrating device), or shaking the mold/container, or hard impulses, which are laterally or from below on the Mass 2 act, e.g. B. by hitting against the mold / container 1, compacted so that a compact mass 2 is formed.
• the wheat or corn starch can be a binder be mixed in.
• Sugar or an oil, e.g. cooking oil, is particularly suitable as a binding agent for the preparation of the mixture.
• High-temperature-resistant polymers carbon black, graphite dust, natural graphite, PVA (polyvinyl alcohol) adhesive, for example, come into consideration as further graphitizable materials.
• natural fibers such as cotton, cellulose, bamboo, hemp, etc. can also be added.
• a shrinking process is then triggered by heating the compact or compacted mass 2 in the filled mold/container 1 in an oven to a first temperature level of 170°C - 450°C in an oxidizing or inert atmosphere or at >170°C and the mass 2 is stabilized in the mold/container 1 over a longer period of time.
• the stabilization takes place over a period of >1 hour depending on the amount of mass 2.
• Fig. 1b shows the at least partially carbonized mass 3 after the first thermal treatment and
• Fig. 3 shows various views of the at least partially carbonized mass 3 after removal from the mold/container 1.
• the shrinking process can also be triggered by rapid heating of the compact mass 2 to a starting temperature of approx. 190°C, followed by a cooling process over a few hours and renewed slow, stepless heating of the compact mass to 210-230°C.
• the shrinking process can best be triggered by slowly heating up in stages to ⁇ 180°C and 230°C.
• the form / container 1 can be made of a temperature-resistant plastic, or another material, in order to be able to remove the stabilized mass 3 easily, it being alternatively possible for the form / container 1 to be filled with a mass before filling Lining cloth 4 (Fig. 2).
• the at least partially carbonized mass 3 is heated in the furnace in a heating ramp to a second temperature level of >1,000°C for carbonization or to >2,500°C for graphitization under protective gas to form a blank 5 that is as compact as possible, whereupon the blank 5 can be removed from the mold/container 1.
• the noble gases helium, neon, argon, krypton, xenon and radon can be used as protective gases.
• N2 can also be used.
• the blank 5 can also be removed from the mold/the container 1 before the carbonization and graphitization and exposed to the thermal treatment in the furnace.
• the heating ramp for carbonizing or graphitizing the blank 5 should be ⁇ 1°C/min or less, with a pause of ⁇ 30 to 120 minutes at each 50°C to 100°C step so that the material relaxes and at the same time gases such as air or water vapor can diffuse out without damaging the structure.
• the carbonization or graphitization is preferably carried out at a pressure of >500 mbar.
• FIG. 5 shows the blank 5 according to FIG. 4 finished as a shaped body 6 after mechanical processing by turning from both sides (outside and inside).
• the graphite blank 5 produced according to the invention can also be converted into SiC without any problems.
• the conversion into SiC can, as usual, take place in a furnace at a temperature of >1,200° C. with the supply of SiO with argon as the carrier gas at a pressure of 30 mbar.
• the preferred temperature for this process is 1520°C.
• the conversion to SiC can also be done at a high pressure, such as 950 mbar.
• the actual pressure used has an impact on the homogeneity and speed of the conversion.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Carbon And Carbon Compounds (AREA)

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• 2021
  • 2021-11-23 DE DE102021130581.0A patent/DE102021130581A1/de active Pending
• 2022
  • 2022-11-14 WO PCT/EP2022/081768 patent/WO2023094199A1/de not_active Ceased
  • 2022-11-14 CN CN202280075286.2A patent/CN118234681A/zh active Pending
  • 2022-11-14 JP JP2024529759A patent/JP2024543101A/ja active Pending
  • 2022-11-14 EP EP22818239.0A patent/EP4436917A1/de active Pending
  • 2022-11-14 US US18/708,336 patent/US20240417265A1/en active Pending

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