PL167911B1 - Method of obtaining a potassium-bismuth-graphite compound - Google Patents

Abstract

A method of obtaining the intercalated potassium-bismuth-graphite compound consisting of heating the metallic bismuth and metallic potassium until they melt, and then after adding dusty graphite on further heating above the melting point of the mixture, characterized in that heating the metallic bismuth and metallic potassium and intercalating graphite of the obtained K-Bi alloy is carried out under an inert gas atmosphere under pressure about 1 hPa up to a slight overpressure.

Description

The present invention relates to a method for the preparation of an intercalated potassium-bismuth-graphite compound.

In the 1980s, the interest in the synthesis and properties of the so-called 'Triple intercalated graphite compounds with two chemically different types of intercalates.

An interesting group among "triple intercalates" are compounds containing two metals of the type: MT _x C4n, where: T = Hg, Bi, T1 ...; x = 0.55 to 1.55; M = K, Rb, Na, Cs.

In their recent publications, A. Bendriss-Rerhrhaye, JF Maveche, M. McRae, Synth, Metals, 12, 201 (1985) provide the preparation of MT alloys (e.g. KHg, KBi, RbHg etc.) by heating metals under reduced pressure until the liquid phase is obtained. Then, graphite dusty is added to the obtained M-T alloy and further annealed under reduced pressure until the finished product is obtained. Heating is long, e.g. 10 days for the K-Bi-graphite compound. Various compounds are obtained by controlling the temperature and reaction time. These compounds, especially K-Bi-graphite, show a good organization of the layers, which makes it possible to identify their layer structure by the method of X-ray powder diffraction by X-rays. A series of reflections are recorded on the diffraction patterns (001).

The above-presented methods for the preparation of M Tx C4n triple intercalates have a certain disadvantage, which consists in operating and carrying out the reaction of producing the M-T alloy and in carrying out the reaction of this alloy with graphite under reduced pressure.

The aim of the invention is to eliminate vacuum systems that complicate devices for intercalating graphite compounds.

The method according to the invention consists in first heating the metallic bismuth with metallic potassium until it melts, and then, after adding the graphite powder, the obtained mixture is heated at a temperature above the melting point of the mixture in an inert gas atmosphere at a pressure of about 1 hPa to a low hypertension.

Preferably, nitrogen, helium, argon, etc. are used as the inert gas.

The advantage of the process according to the invention is the preparation of a product which, in turn, has recently found numerous applications due to its superconducting properties and, more recently, also due to its catalytic properties.

EXAMPLE 1 2.752 g of metallic bismuth in the form of filings and about 0.6 g of metallic potassium in the form of billets were poured into a glass ampoule.

The ampoule was connected to a vacuum system, degassed to a pressure of about 6 Pa and filled with purified nitrogen gas to a pressure of 1.1 hPa through a suitable valve system. The ampoule was then disconnected and the valves in the vacuum system opened to equilibrate the pressures.

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The opened ampoule was heated to the temperature of 320 ° C and the valves of the vacuum system were closed, and then the ampoule and its contents were heated at this temperature. The K + Bi mixture was heated in this state for 72 h, cooled to ambient temperature and valves opened. 5.437 g of Sri Lanka graphite dust was introduced into the K-Bi alloy. After the graphite was poured in, the ampoule was degassed again to a pressure of about 6 Pa and filled with purified nitrogen. After heating the ampoule with its contents to the temperature of 380 ° C, it was closed and the temperature was maintained at 380 ° C for 264 hours.

After the annealing process was completed, the ampoule was cooled and aerated, then broken and the product was extracted. The product was tested by X-ray fluorescence. The obtained results show that the product has the following composition: K Bio, 94 Ce, 65. The X-ray diffraction studies indicate that this compound with an increased total composition was in fact a mixture of unreacted graphite (d = 335 µm) and the new K-Bi-C phase with an identity limit of 2640 µm (001). There were reflections in the diffraction pattern constituting the (001) series from this layered compound: 1320 µm (002); 440 pm (003); 660 pm (004); 528 pm (005); 440 pm (006); 377 pm (007); 330 pm (008); 293 pm (009); 264 pm (0010).

Example II. 3.54 g of metallic bismuth in the form of filings and about 0.8 g of metallic potassium in the form of billets were poured into a glass ampoule.

The ampoule with poured substrates was purged with purified nitrogen.

The opened ampoule was heated to 320 ° C and the valves of the vacuum system were closed. The sealed ampoule was heated for 96 hours, then cooled to room temperature and opened. 7.10 g of Sri Lanka graphite powder were sprinkled into the obtained K-Bi alloy. The ampoule was refilled with gaseous purified nitrogen. After heating the open ampoule with its contents at a temperature of 380 ° C, it was closed and annealed in this state and at this temperature for 292 hours.

After cooling, the ampoule was aerated, broken up and the product was extracted. By X-ray diffraction the product was found to contain unreacted graphite (d = 335 µm) and the K-Bi-graphite compound with a periodic structure with an identity period of 2640 µm, with a corresponding (001) series of X-ray reflections.

Example 3 3.6 g of metallic bismuth in the form of filings and about 0.9 g of metallic potassium in the form of billets were poured into a glass ampoule.

The ampoule was purged with purified argon. The open ampoule was heated to a temperature of 320 ° C and then heated at this temperature for 96 hours. In the product taken out of the ampoule, a mixture of phases was also found, in which unreacted graphite and the K-Bi-graphite compound with a periodic structure with an identity period of 2640 µm and a corresponding series of X-ray reflections were separated.

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Claims (2)

Patent claims 1. The method of obtaining the intercalated potassium-bismuth-graphite compound by heating metallic bismuth and metallic potassium until they melt, and then after adding the graphite dust on further heating above the melting point of the mixture, characterized in that heating metallic bismuth and metallic potassium and intercalating graphite of the obtained K-Bi alloy is carried out in an inert gas atmosphere at a pressure of about 1 hPa until a slight overpressure. 2. The method according to p. A process as claimed in claim 1, characterized in that nitrogen, helium, argon, etc. are used as the inert gas.