KR102394514B1 - Zinc-doped magnesium silicate - Google Patents

Abstract

The present invention relates to magnesium silicate. In order to provide magnesium silicate which can be sintered at temperatures of up to 1200 °C (≤ 1200 °C), magnesium silicate is based on the general formula Mg _x Zn _y X _z [SiO ₄ ], wherein 1.00 ≤ x ≤ 1.99 , 0.01 ≤ y ≤ 0.32, 0 ≤ z ≤ 0.10, and X is calcium and/or manganese and/or iron. The invention also relates to a corresponding ceramic material, a corresponding injection molding component, a corresponding manufacturing method, as well as a high-temperature cell and an energy system, in particular a cogeneration system.

Description

Zinc-doped magnesium silicate {ZINC-DOPED MAGNESIUM SILICATE}

The present invention relates to a magnesium silicate, a corresponding ceramic material, a corresponding injection molding component, a corresponding manufacturing method, as well as a high-temperature cell and an energy system.

High-temperature fuel cells, also referred to as Solid Oxide Fuel Cells (SOFCs), can be used for generation of current and heat, such as in auxiliary units or combined heat and power systems (KWKs).

A subject of the present invention is magnesium silicate containing zinc. Thus, for example, magnesium silicate can also be referred to as magnesium zinc silicate. In particular, magnesium silicate is based on the general formula (Mg,Zn) ₂ [SiO ₄ ].

In this case, the expression "based on" means in particular that the magnesium silicate may contain one or a plurality of additional elements, optionally as dopants, in addition to the elements shown in the general formula.

Besides magnesium and zinc, magnesium silicates may in particular contain calcium and/or manganese and/or iron. In particular the magnesium silicate may be doped with calcium and/or manganese and/or iron.

In the scope of one embodiment, the magnesium silicate is based on, or has the general formula Mg _x Zn _y X _z [SiO ₄ ].

In this case, X may for example be one or a plurality of polyvalent, in particular divalent cations. For example, X may be calcium and/or manganese and/or iron.

In this case, for example, 1.00 ≤ x ≤ 1.99. for example 1.65 or 1.68 ≤ x ≤ 1.99 or 1.98 or 1.95 or 1.94 or 1.90 or 1.87 or 1.85 or 1.83 or 1.80 or 1.77.

In this case, for example, 0.01 ≤ y ≤ 0.32. in particular 0.01 or 0.05 or 0.06 or 0.10 or 0.15 or 0.17 or 0.20 or 0.23 or 0.25 ≤ y ≤ 0.32.

In some cases 0 ≤ z ≤ 0.10, and thus in particular 0 < z ≤ 0.10. for example 0 ≤ z ≤ 0.10 or 0.09 or 0.08 or 0.07 or 0.06 or 0.05 or 0.04, and thus in particular 0 < z ≤ 0.10 or 0.09 or 0.08 or 0.07 or 0.06 or 0.05 or 0.04. In some cases, 0.01 ≤ z ≤ 0.10 or 0.09 or 0.08 or 0.07 or 0.06 or 0.05 or 0.04.

Through the magnesium silicate containing or doped with zinc, the sintering temperature of about 1385° C. for pure magnesium silicate of the general formula Mg ₂ [SiO ₄ ], preferably also called forsterite, can be lowered, Magnesium silicate can be provided which can already be densely sintered at a temperature of 1200° C. or lower (≤ 1200° C.).

Through the magnesium silicate containing magnesium and zinc in the above amounts, preferably a single-phase microstructure can be achieved.

This has been shown to be particularly desirable for the production of high-temperature cells, which will be described later. Such high-temperature cells can in particular be produced by co-sintering of various materials, ie by co/co-sintering. In this case, preferably all relevant materials should be able to achieve their maximum sintering at the sintering temperature, and in particular in that case should not decompose or burn or participate in undesirable side effects. However, particularly undesirable reactions may occur at sintering temperatures above 1200° C. (>1200° C.). For example, an undesirable reaction of zirconium dioxide, which can be used as an electrolyte material, and lanthanum-strontium-manganese oxide (LSM), which is a cathode material, may occur, forming a highly insulating foreign phase, for example. It is particularly advantageous for the formation of airtight end sections, such as airtight tube caps and airtight connecting flanges/mounting flanges, that the magnesium silicate according to the invention can already be densely sintered at temperatures up to 1200 °C (≤ 1200 °C). In this case, it is possible to prevent an unintended leakage of combustion gases, in turn, preferably.

Overall, therefore, preferably low-sintering magnesium silicate and thus forsterite-based and low-sintering ceramic materials are particularly advantageous for high-temperature fuel cells (solid oxide fuel cells, SOFCs) and/or high-temperature electrolyte cells (solid oxide electrolyte cells, SOEC). ) and/or for the manufacture of high temperature cells such as high temperature metal-air cells.

Preferably, not only dense sinterability can be achieved under conditions of 1200° C. or less (≤ 1200° C.) with zinc, but also the following pure forsterite (Mg ₂ [SiO ₄ ]) Chemical and physical properties can also be maintained, since zinc can be incorporated into the M ₂ [SiO ₄ ] or forsterite crystal lattice.

- electrical insulation,

- suitable thermal expansion, especially matched to other high temperature cell components, such as electrolyte (~ 10 ppm/K),

- chemical stability to eg other high-temperature cell components, not only in sintering conditions, but also during operation, eg over a wide oxygen partial pressure range (10 ^-24 atm < pO ₂ < 1 atm), and

- Dense and porous sinterability.

Polyvalent (heterogeneous) cations (calcium and/or manganese and/or iron) entering the crystal structure can preferably broaden the ion lattice, and enable a relatively higher sintering density by enhanced diffusion while It is possible to further increase the sintering activity.

Through the magnesium silicate containing polyvalent (heterogeneous) cations (calcium and/or manganese and/or iron) in the above amounts, preferably good electrical insulating strength can be achieved.

Within the scope of a particular embodiment, 1.65 or 1.68 ≤ x ≤ 1.85 or 1.83, such as 1.65 or 1.68 ≤ x ≤ 1.80 or 1.77.

Within the scope of a particular embodiment, 0.15 ≤ y 0.32, eg. 0.23 ≤ y ≤ 0.32. for example 0.17 or 0.20 or 0.23 or 0.25 ≤ y ≤ 0.32.

Within the scope of a particular embodiment, 0 ≤ z ≤ 0.05, in particular 0 < z ≤ 0.05, eg. 0.01 ≤ z ≤ 0.05.

Within the scope of a further embodiment, 0 ≤ z ≤ 0.03, in particular 0 < z ≤ 0.03, such as 0.01 ≤ z ≤ 0.03. For example, z = 0.016.

In particular, it may be x + y + z = 2.

In particular, magnesium silicate may be doped with calcium. A further improvement in sinterability can thus advantageously be achieved.

Therefore, within the scope of a further embodiment, X is calcium.

In the scope of a further embodiment, the magnesium silicate is an island silicate. In particular the magnesium silicate may be olivine.

Olivine is an Irish silicate with the general formula M ₂ [SiO ₄ ]. Oxygen ions in this structure can form spherical, particularly approximately hexagonal close packing of spheres. In this case, the relatively smaller silicon (Si ^{4 +} ) may occupy a portion of the tetrahedral sites in particular. Therefore, in particular, some of the tetrahedral interstitial sites can be filled with silicon atoms. In this case, the relatively larger M cations can occupy particularly octaherdral sites.

When the M site is completely filled with magnesium (Mg), magnesium silicate is also called forsterite.

However, in the case of the magnesium silicate according to the invention, the M sites or octahedral intercalation sites are only partially by magnesium (Mg), and partly by zinc (Zn), and in some cases also partly by calcium and/or or another polyvalent, in particular divalent cation, such as manganese and/or iron.

For further technical features and advantages of the magnesium silicate according to the invention, the ceramic material according to the invention, the injection molding component according to the invention, the manufacturing method according to the invention, the high-temperature cell according to the invention, Reference is made to the drawings and the description of the embodiments, as well as the description relating to the energy system that follows, in particular the cogeneration system according to the invention.

A further subject of the invention is a ceramic material containing or formed from the magnesium silicate according to the invention.

For further technical features and advantages of the ceramic material according to the invention, the magnesium silicate according to the invention, the injection molding component according to the invention, the manufacturing method according to the invention, the high-temperature cell according to the invention, Reference is made to the drawings and the description of the embodiments, as well as the description relating to the energy system that follows, in particular the cogeneration system according to the invention.

Furthermore, the present invention relates in particular to an injection molding component for the formation of the magnesium silicate and/or ceramic material according to the invention. The injection molding component may in particular comprise starting materials for the formation of the magnesium silicate according to the invention. For example, the injection molding component may be magnesium silicate and/or magnesium silicate hydrate, for example in the form of talc, and/or magnesium oxide and zinc oxide and/or zinc silicide, and optionally calcium carbide and/or calcium silicide and/or calcium oxide. and/or manganese silicide and/or manganese oxide and/or manganese carbide and/or iron silicide and/or iron oxide and/or iron carbide. In addition, the injection molding component may in particular comprise one or more binders. The one or more binders may be burned, for example, during sintering. Thus, for example, an airtight ceramic material can be produced.

Within the scope of a particular embodiment, the injection molding component contains one or more pore formers. The one or more pore formers burn off during sintering and pores remain. Thus, for example, a gas permeable porous ceramic material can be produced.

For further technical features and advantages of the injection molding component according to the invention, the magnesium silicate according to the invention, the ceramic material according to the invention, the manufacturing method according to the invention, the high-temperature cell according to the invention, Reference is made to the drawings and the description of the embodiments, as well as the description relating to the energy system that follows, in particular the cogeneration system according to the invention.

A further subject of the invention is a production process for the production of magnesium silicates, such as ceramic materials and/or injection molding components.

In the process herein, in particular the starting materials for the formation of magnesium silicate can be pulverized by means of a mill, in particular in stoichiometric amounts. The starting materials are therefore preferably finely pulverized from the outset and in particular can be mixed with one another homogeneously. The grinder may be, for example, an agitator ball mill.

The starting materials or raw materials are, for example, magnesium silicate and/or magnesium silicate hydrate, for example in the form of talc, and/or magnesium oxide and zinc oxide and/or zinc silicide, and optionally calcium carbide and/or calcium silicide and/or calcium oxide and/or manganese silicide and/or manganese oxide and/or manganese carbide and/or iron silicide and/or iron oxide and/or iron carbide.

The process herein results in a powder comprising particles whose particle shape is substantially spherical, which is single-origin during plastic processing to form an injection molding component (injection molding compound). It has the advantage that it can be packed much better than the plate-shaped forsterite powder of In this case, a higher packing density in the green body can be given, preferably with a much better sintering capacity and compressibility and a lower shrinkage than with a loose packing density.

In particular the starting materials may first be suspended or dispersed in water, in particular in stoichiometric amounts, and then pulverized by means of a mill. Preferably a particularly fine distribution of the starting materials can be achieved. For this purpose, eg magnesium silicate and/or magnesium silicate hydrate, eg in the form of talc, and/or magnesium oxide and zinc oxide and/or zinc silicide, and optionally in small amounts of calcium carbide (CaCO ₃ ) [or calcium carbide As an alternative to or in addition to manganese oxide, iron oxide or the respective carbides and/or silicides], starting materials may be used in the amounts of substances calculated previously stoichiometrically.

For example, ^the partial replacement of ^{Mg 2+} with Zn ²⁺ can be carried out in the range of 1 weight percent or more to 23 weight percent or less, especially compared to pure forsterite. Optionally, addition of Ca and/or Mn and/or Fe in the range of 0.1% by weight or more to 5% by weight or more, in particular 0.2% by weight or more to 2% by weight or less, in addition to the Zn doping may be carried out.

Suspension or dispersion can be effected, for example, using a disperser such as Tegodispers W741 (TEGO). After suspending or dispersing in water, the mixture can be finely ground, for example immediately in a stirred ball mill. Multiple passes through the mill may be practiced. For example, four passes through the grinder were found to be sufficient.

Moisture can then be removed from the suspension or dispersion by thermal drying. Thus, preferably a homogeneous powder mixture can be achieved.

The dried mixture may then be calcined, for example, at a temperature ranging from 900° C. or higher to 1100° C. or lower (900° C. ≤ temperature ≤ 1100° C.). The calcination can in particular be carried out in a furnace. For example, calcination may be performed with a holding time of 5 hours. The doped forsterite powder thus obtained is ready for use for injection molding components or compound synthesis.

For further technical features and advantages of the production process according to the invention, the magnesium silicate according to the invention, the ceramic material according to the invention, the injection molding component according to the invention, the high-temperature cell according to the invention, Reference is made to the drawings and the description of the embodiments, as well as the description relating to the energy system that follows, in particular the cogeneration system according to the invention.

The present invention also relates to a high temperature wherein at least one section is formed from a magnesium silicate according to the invention, or from a ceramic material according to the invention, or from an injection molding component according to the invention, or from a magnesium silicate prepared according to the invention. It relates to cells, in particular fuel cells and/or electrolyte cells and/or metal-air cells.

A high-temperature cell is in particular a ceramic electrochemical cell, such as a high-temperature fuel cell (solid oxide fuel cell, SOFC) and/or a high-temperature electrolyte cell (solid oxide electrolyte cell, SOEC), which is operated at high temperatures (≥ 500°C), for example at least 500°C. ) and/or high temperature metal-air cells. In this case, the high-temperature cell in particular can be a high-temperature fuel cell (SOFC) and/or a high-temperature electrolyte cell (SOEC) and/or a high-temperature metal-air cell.

In the scope of one embodiment, the high temperature cell is in particular a tubular cell of ceramic. In this case, the tubular cell may in particular comprise a hollow cylindrical middle section and two end sections. In this case, one of the end sections may in particular be an open fixed section, for example a connecting flange or a mounting flange. The other end section may be a cap section or tube cap closing the hollow cylindrical middle section (tubular cell closed on one side). However, it is likewise also possible for the other end section to be a particularly open fixed section, for example a connecting flange (tubular cell open on both sides). In this case, the hollow cylindrical intermediate section may in particular have a functional layer system, for example consisting of an anode layer, a cathode layer and an electrolyte layer disposed between these layers.

The hollow cylindrical intermediate section can in particular be formed of a gas permeable porous ceramic material. The end sections can be formed from a particularly airtight ceramic material.

In this case, in particular the hollow cylindrical intermediate section and/or the end sections are made of magnesium silicate according to the invention, or of a ceramic material according to the invention, or of an injection molding component according to the invention, or of magnesium produced according to the invention. It can be formed from silicates. In this case, a particularly gas-permeable porous hollow cylindrical intermediate section can be formed, for example, by the injection molding component according to the invention containing a pore former, the in particular airtight end sections of the invention free of the pore former It may be formed by an injection molding component according to

For further technical features and advantages of the high-temperature cell according to the invention, obviously the magnesium silicate according to the invention, the ceramic material according to the invention, the injection molding component according to the invention, the manufacturing method according to the invention, the present invention Reference is made to the drawings and the description of the embodiments, as well as the description relating to the energy system according to the invention, in particular the cogeneration system according to the invention.

The invention also relates to a high-temperature cell according to the invention and/or a magnesium silicate according to the invention and/or a ceramic material according to the invention and/or an injection molding component according to the invention and/or magnesium produced according to the invention. It also relates to energy systems comprising silicates, in particular combined heat and power systems (KWK). In particular, the cogeneration system may be a micro cogeneration system (μKWK).

For further technical features and advantages of the energy system according to the invention, in particular of the cogeneration system according to the invention, the magnesium silicate according to the invention, the ceramic material according to the invention, the injection molding component according to the invention, the present invention Reference is made to the drawings and the description of embodiments, as well as to the description relating to the manufacturing method according to the invention, the high-temperature cell according to the invention.

Further advantages and preferred embodiments of the objects according to the invention are shown by the drawings and are explained below. It should be noted that the drawings have only the features described and should not be construed as limiting the invention in any way.

1 is a schematic graph of a dilatometer measurement;
Fig. 2 is a schematic cross-sectional view showing one embodiment of a tubular high-temperature cell according to the present invention.
3 is a schematic cross-sectional view showing another embodiment of a tubular high-temperature cell according to the present invention.

In Fig. 1, the results of dilatometric measurements for three inventive samples 1, 2 and 3 of Zn-doped magnesium silicate or Zn-doped forsterite are shown.

For sample 1, magnesium silicate contains 20 weight percent zinc silicide and has the formula Mg _1.73 Zn _0.27 [SiO ₄ ].

For sample 2, magnesium silicate contains 10 weight percent zinc silicide and has the formula Mg _1.87 Zn _0.13 [SiO ₄ ].

For sample 3, magnesium silicate contains 5 weight percent zinc silicide and has the formula Mg _1.94 Zn _0.06 [SiO ₄ ].

1, the shrinkage rate (S) in percent is plotted against the temperature (T) in degrees Celsius and the holding time in hours at a sintering temperature of 1200°C. The sintered density of Sample 1 was about 3.31 g/cm 3 .

1, it is shown that all three samples have a sintering temperature of less than 1200° C. and thus improved sintering properties. In figure 1 it is shown that the sintering motion depends on the degree of zinc doping. In this case, the lowest sintering temperature was found for sample 1, which preferably contained 20 weight percent zinc.

In the lower curve on the left of FIG. 1 , in which the shrinkage S is plotted as a function of temperature T during heating, it is shown that the heat treatment is initiated at a shrinkage of 0%. With increasing temperature, the samples expand weakly due to their coefficient of thermal expansion of ~10 ppm/K. From 1000°C, the samples begin to shrink.

The more zinc the samples contain, the faster the shrinkage begins, ie for sample 1 with a maximum Zn ₂ SiO ₄ -content of 20 weight percent, the shrinkage leads to a minimum zinc content of 5 weight percent Zn ₂ SiO ₄ . It starts about 100K earlier than the case of sample 3 with During the holding time the sample bodies are further compressed. This can also be confirmed from the curve on the right side of FIG. 1 in which the shrinkage rate (S) is displayed according to the holding time (t) at a sintering temperature of 1200°C.

In the upper curve on the left of Figure 1, where the shrinkage rate (S) is plotted as a function of temperature (T) during cooling, sintering is terminated upon the cessation of holding time and onset of cooling and the samples have a coefficient of thermal expansion of ~10 ppm/K. As a result, only a weak contraction appears.

2 and 3 show different embodiments of high temperature cells 10 according to the present invention. 2 and 3 it is shown that the high temperature cells 10 are formed as a tubular cell comprising a hollow cylindrical intermediate section 11 and two end sections 12 , 13 .

2 and 3 it is shown that the cell 10 is formed in this case in particular as a tubular cell closed on one side. One of the end sections 12 is formed as an open fixed section or a connecting flange/mounting flange. In this case, the other end section 13 is formed as a cap section (or tube cap) which closes the hollow cylindrical intermediate section 11 .

2 and 3 , it is shown that the hollow cylindrical intermediate section 11 has a functional layer system 14 . The functional layer system 14 is precisely on the inner surface of the hollow cylindrical intermediate section 11 in the scope of the embodiment shown in FIG. 2 and on the outer surface of the hollow cylindrical intermediate section 11 in the scope of the embodiment shown in FIG. 3 . It is arranged at the height of the porous hollow cylindrical intermediate section (11).

In this case, the wall portion of the hollow cylindrical intermediate section 11 is formed of a highly porous and gas-permeable ceramic material, and the end sections 12 and 13 (mounting flange and tube cap) are formed of an airtight ceramic material.

The tube formed by the hollow cylindrical intermediate section 11 is used in particular as an electrochemically inert carrier and makes it possible to implement very thin functional layers of the functional layer system 14 . The functional layer system, for example, comprises an electrolyte layer made of, for example, zirconium oxide stabilized with yttrium and having a layer thickness of 50 μm or less (≤ 50 μm), which electrolyte layer may easily rupture in case of thermal mismatch.

In particular, pure magnesium silicate of formula Mg ₂ SiO ₄ , also called forsterite, is already in functional layers with respect to its shrinkage, its thermal expansion, its electrical insulating properties, and its chemical stability to other battery components. It has been proven as an excellent partner for

However, pure magnesium silicate (forsterite) of the formula Mg ₂ SiO ₄ can be densely sintered at about 1385°C. However, at temperatures in excess of 1200°C, undesirable side effects of e.g. zirconium dioxide-electrolyte and lanthanum-strontium-manganese oxide-cathode materials can occur, in some cases forming highly insulating heterophases, at temperatures lower than or equal to 1200°C The sintering of pure magnesium silicate (forsterite) of the formula Mg ₂ SiO ₄ may in some cases not give rise to the desired tightness of the end sections 12 , 13 in particular and in some cases may lead to combustion gas leakage. .

2 and 3 , in order to be able to cosinter the high temperature cell 10 , such as a fuel cell, in a single heat treatment, and in particular with a wide variety of available materials, including for example lanthanum-strontium manganese oxide (LSM). In the case of the cell 10 shown in , the end sections 12 and 13 and the hollow cylindrical middle section are formed of magnesium silicate containing zinc. In this case, the gas-permeable porous hollow cylindrical intermediate section 11 can be formed, for example, by an injection molding component according to the invention containing a pore former, the airtight end sections 12 , 13 being porous forming. It can be formed by the injection molding component according to the present invention which does not contain an agent.

In addition, it is shown in FIGS. 2 and 3 that the gas supply lance 15 is inserted into the inner chamber of the tubular cell 10 via an open fixing section 12 .

1: sample
2: sample
3: sample
10: high temperature battery
11: middle section
12: end section
13: end section
14: functional layer system
15: gas supply lance

Claims (11)

Magnesium silicate based on the general formula:
Mg _x Zn _y X _z [SiO ₄ ]
In the above formula,
1.65 ≤ x ≤ 1.85,
0.25 ≤ y ≤ 0.32,
0 < z ≤ 0.10,
X is calcium or manganese or iron, magnesium silicate. delete delete The magnesium silicate of claim 1 , wherein the magnesium silicate is an island silicate. A ceramic material comprising the magnesium silicate according to claim 1 . An injection molding component containing starting materials for the formation of magnesium silicate according to claim 1 . 7. The injection molding component of claim 6, wherein the injection molding component further contains one or more pore formers. Process for the production of magnesium silicate according to claim 1 , wherein the starting materials for the formation of magnesium silicate according to claim 1 are pulverized by means of a mill. At least one section of the cell is made of a magnesium silicate according to claim 1, or a ceramic material according to claim 5, or an injection molded component according to claim 6, or a magnesium silicate prepared by a method according to claim 8. A high-temperature cell formed. A high temperature cell (10), said high temperature cell being a tubular cell comprising a hollow cylindrical intermediate section (11) and two end sections (12, 13), said hollow cylindrical intermediate section (11) comprising a functional layer system ( 14), wherein the hollow cylindrical intermediate section (11) is formed of a gas-permeable porous ceramic material, and the end sections (12, 13) are formed of a gas-tight ceramic material, the hollow cylindrical intermediate section (11) 11) and/or the end sections (12, 13) are made of magnesium silicate according to claim 1, or of a ceramic material according to claim 5, or of an injection molded component according to claim 6, or of claim 8 A high temperature cell formed from magnesium silicate prepared by the method according to A high-temperature cell, wherein at least one section of said high-temperature cell is made of a magnesium silicate according to claim 1 , or a ceramic material according to claim 5 , or an injection molded component according to claim 6 , or in a method according to claim 8 . comprising the high-temperature cell, which is formed of magnesium silicate prepared by
comprising the magnesium silicate according to claim 1, or
comprising the ceramic material according to claim 5, or
comprising the injection molding component according to claim 6, or
An energy system comprising magnesium silicate prepared by the method according to claim 8 .

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