RU2522492C2 - Production of gas-proof ceramics for electrochemical devices - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to production of gas-proof ceramics with mixed ion-electron conductivity. Proposed process comprises production of oxide-organic binder and plasticiser, forming of preset-shape blanks roasting to sintering. Four percent solution of CKH-26M-grade butadiene-nitrile rubber obtained in the mix of acetone and gasoline taken in 3:2 ratio is used as said binder. Five percent solution of dibutyl phthalate in gasoline is used as said plasticiser. Note here that oxide powder is mixed with organic binder at the ratio of 1 ml of solution per 1 g of powder while with plasticiser it is mixed at the ratio of 1 ml of solution per 40 g of powder. Claimed method allows making of ceramics based on lanthanum-strontium cobaltites and manganites, strontium titanate-ferrites and zirconium oxide-based systems.

EFFECT: better ductility suitable for production of ceramics for electrochemical devices.

8 dwg

Description

              The invention relates to the manufacture of gas-tight oxide ceramics with mixed ion-electron conductivity and can be used in the development of elements of electrochemical devices, in particular membranes to produce pure hydrogen or oxygen and others.

It is known, for example, that gas-tight ceramics of the composition Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-δ (BSCF) are made by slip casting from a composite oxide material (M.-B. Choi, D.-K. Lim, S.-Y. Jeon, H.-S. Kim, S.-J. Song. Oxygen permeation properties of BSCF5582 tubular membrane fabricated by the slip casting method. Ceramics International. 38 (2012), p. 1867) [1]. To obtain a suspension of oxide material, BSCF oxide powder is mixed with a solvent (ethanol), a dispersant (ammonium polycarbonate), polyester, plasticizer (PEG 400 polyethylene glycol) and a binder (polyvinyl alcohol). The suspension is poured into the cavity of a microporous injection mold and kept in it. Under the action of capillary forces, the solvent is removed from the inner cavity, and a gel layer forms on the inner surface of the injection mold. The remainder of the suspension is poured from the injection mold, and the mold is dried. Billets extracted from the injection mold are sintered to produce finished gas-tight ceramic products.

Gas tight ceramics with the composition La _0.7 Ca _0.3 Fe _0.85 Co _0.15 O _3-δ (LCFC) are also obtained by plastic extrusion from a composite oxide material (M. Trunecw, J. Cihlar. Tubular La _0.7 Ca _0.3 Fe _0.85 Co _0.15 O _3-δ Perovskite Membranes , Part I: Preparation and Properties. J. Am. Ceram. Soc. 89 (2005), p. 949) [2]. To obtain it, the oxide powder of LCFC material and a binder are mixed, as a mixture of ethylene vinyl acetate and paraffin wax. The resulting mixture was added to stearic acid, homogenized and dried. The dried mixture is placed in an extruder, squeezed out through a die, the obtained billets are sintered to the finished gas-tight ceramic products.

A gas-tight two-layer oxide ceramic of the composition La _0.8 Sr _0.2 MnO _3-δ (LSM) of a tubular form on a porous substrate Zr _0.7 Y _0.3 O _2-δ (YSZ) is obtained from a composite oxide material in the form of a colloidal suspension, the solid phase of which is LSM oxide powder, liquid phase - a mixture of polyvinyl butyral, fish oil, dibutyl phthalate and Span-80 sorbitan oleate in a mixture of toluene and methyl ethyl ketone (X. Yin, C. Choong, L. Hong, Z. Liu. Crafting La _0.2 Sr _0.8 MnO _3-δ membrane with dense surface from porous YSZ tube. J. Solid State Electrochem. 10 (2006), p.643) [3]. A porous tube is immersed in this suspension, dried and sintered to the finished product.

Ceramic products made by the above methods have limitations in shape and size. So, the dimensions of the workpieces in the slip casting method are determined by the dimensions of the injection mold, it is difficult to obtain products with a wall thickness of less than 0.25 mm by the plastic extrusion method, when using the immersion method, it is possible to obtain products with an uneven distribution of the deposited layer on the surface of the porous substrate.

In addition, the known methods are characterized by the complexity of manufacturing ceramic products, because require strict technological control over the quality of the suspension, the exact amount of organic components introduced into the powder and the condition of the auxiliary devices, as well as a narrow size distribution of the initial powder particles or the need to take into account the requirements for the porous position during the immersion process used in the method [3] .

The objective of the present invention is to develop a method of manufacturing gas-tight ceramics for electrochemical devices of various shapes and sizes while simplifying manufacturing techniques.

To solve this problem, a method for the manufacture of gas-tight ceramics for elements of electrochemical devices is proposed, which includes the preparation of organic oxide by mixing oxide powder with an organic binder and plasticizer, followed by the formation of preforms of a given shape and firing to obtain sintered products, moreover, upon receipt of organic oxide in 4% solution of nitrile butadiene rubber SKN-26M, obtained in a mixture of acetone and gasoline taken in A removable ratio of 3: 2, a 5% solution of dibutyl phthalate in gasoline is used as a plasticizer, while the oxide powder is mixed with an organic binder in the ratio of 1 ml of solution to 1 g of powder, with a plasticizer in the ratio of 1 ml of solution to 40 g of powder.

The experimentally selected concentrations of nitrile butadiene rubber solution, plasticizer and solvents made it possible to obtain a combination of viscosity, ductility and strength of the organic oxide mass, sufficient so that this mass could be rolled after drying to obtain plates. From the ceramic obtained by rolling in the form of plates, it is possible to manufacture elements of electrochemical devices of various shapes and sizes, for example, tubular, complex, irregular shapes, etc. This simplifies the manufacturing technology of gas-tight ceramic products. Failure to comply with the conditions of the implementation of the method will not allow to form plates from the dried mass, or to obtain dense products, since during the sintering of billets due to the oxidation of rubber and plasticizer to gaseous H ₂ O, CO, CO ₂ and N ₂ , a large amount of gas is produced, resulting to the destruction of ceramics. When using the proposed method for producing gas-tight ceramics, expensive equipment, the use of specific reagents, and powders with a narrow particle distribution are not required.

A new technical result achieved by the claimed invention is to obtain and use organic-oxide mass with properties that allow to obtain ceramic products of various shapes and sizes for elements of electrochemical devices.

The proposed method is illustrated by photographs of the manufacturing process of tubular ceramic products, including the preparation of synthesized powder (Fig. 1), the addition of an organic binder and a plasticizer (Fig. 2), mixing the mixture and pouring onto a fluoroplastic substrate, followed by drying of the mixture (Fig. 3), rolling dried mass with the receipt of the plates (Fig.4, 5), the formation of tubular products (Fig.6). In Fig.7 presents tubular billets in the backfill, Fig.8 - finished sintered tubular products.

To obtain an oxide-organic mass based on strontium titanate-ferrite, a 4% solution of nitrile butadiene rubber was initially prepared. Used rubber brand SKN-26M, it was dissolved in a mixture of acetone and gasoline, taken in a volume ratio of 3: 2. The resulting 4% solution of rubber was added to the initial oxide powder SrTi _0.5 Fe _0.5 O _3-δ in the ratio of 1 ml of solution to 1 g of powder, after which a 5% solution of dibutyl phthalate in gasoline was introduced in the ratio of 1 ml of solution 40 g of powder. The mixture was thoroughly mixed, the PTFE substrate was poured until the obtained oxide-organic mass was completely dried. The dried mass was rolled on rollers with the required gap thickness to obtain plates.

From the obtained plates, blanks of products of a given shape (tubular, complex, irregular shape, etc.) were obtained, which were burned in a bed of alumina to obtain finished ceramic products. For example, the resulting plates were twisted into tubes, creating a joint and rolling it with a roller for the purpose of fastening. The tubular blanks were fired.

The results of hydrostatic weighing of sintered ceramic products from the material obtained by the claimed method, indicate the receipt of gas-tight ceramics: its relative density is 96% of theoretical.

The claimed method can be used to obtain gas-tight ceramics based on cobaltites and manganites of lanthanum-strontium, titanate-ferrite strontium, systems based on zirconium oxide. Exceptions are oxide systems subject to strong hydration, for example, oxides of alkaline (Li, Na, K, Cs) and alkaline earth (Ca, Ba) elements, since in this case the surface of the hydrated powder is not wetted by the organic mixture.

Thus, the claimed invention allows the manufacture of gas-tight ceramics for elements of electrochemical devices of various shapes and sizes while simplifying the technology for its manufacture.

Claims (1)

A method of manufacturing gas-tight ceramics for elements of electrochemical devices, including obtaining organic oxide by mixing oxide powder with an organic binder and a plasticizer, followed by the formation of preforms of a given shape and firing to obtain sintered products, characterized in that when producing organic-oxide mass as an organic binder use a 4% solution of nitrile butadiene rubber brand SKN-26M, obtained in a mixture of acetone and gasoline taken in a volume ratio of 3: 2, as Your plasticizer uses a 5% solution of dibutyl phthalate in gasoline, while the oxide powder is mixed with an organic binder in a ratio of 1 ml of solution per 1 g of powder, with a plasticizer in a ratio of 1 ml of solution per 40 g of powder.

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