Intercalation compounds, method for preparing them and use there

Details Intercalation compounds, method for preparing them and use there Intercalation compounds, method for preparing them and use there

1998-01-02

1999-10-26

Le, Hoa T.

Stock material or miscellaneous articles

Coated or structually defined flake, particle, cell, strand,...

Particulate matter

252506, 2525191, 25251933, 2525215, 423119, 4232061, 423445R, 423448, 428704, B32B 516, C01D 1300

Patent

active

059725060

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The subject of the invention is new intercalation compounds. The invention is also targeted at a process for the preparation thereof and at the use thereof, in particular in pyrotechnics.


BACKGROUND OF THE INVENTION

It is known to prepare materials capable of generating a sufficient amount of heat on contact with air to be able to be used in pyrotechnics. These materials are generally provided in a pulverulent form and are in particular inorganic compounds.
Among inorganic compounds, alloys and inter-metallic compounds can a priori offer good prospects. Calcium-based alloys are advantageous, for example: they are hard, brittle, can easily be detrimentally affected by water and exhibit exploitable melting temperatures. By way of illustration, the melting temperature of Ca.sub.2 Sn is 1120.degree. C. and that of CaSn.sub.3 is 627.degree. C.
Mention may also be made of calcium-magnesium alloys MgCa or Mg.sub.2 Ca for which the melting temperatures are 517 and 714.degree. C. respectively. Mention may further be made of calcium-zinc alloys, for example ZnCa for which the melting temperature is 385.degree. C.
The enthalpies of reaction (.DELTA.H) are as follows, assuming that the oxides are formed according to a reaction of the type ##EQU1##


______________________________________ 1 .DELTA.H (kcal .multidot. mol.sup.-1) ______________________________________ Ca.sub.2 Sn 2 -442 CaSn.sub.3 3.5 -568 Mg.sub.2 Ca 1.5 -449 MgCa 1 -300 ZnCa 1 -235 ______________________________________
Alloys based on sodium and on potassium have been widely studied for possible pyrotechnic applications. It has thus been possible to demonstrate that some of these alloys, for example the sodium-potassium alloy containing 50-80% by mass of potassium, may be potentially advantageous in pyrotechnics. This is because some of them react in the presence of oxygen or of water with a strong release of heat.
As regards the intermetallic compounds formed with sodium or potassium, their reaction with air is less violent that when Na or K are alone, which is per se a positive point.
Titanium forms a great many binary or ternary alloys with most of the elements of the periodic classification (nouveau traite de Chimie Minerale [New Treatise on Inorganic Chemistry], Paul Pascal, Masson).
Metallic titanium has the property of spontaneously oxidizing in the presence of oxygen, releasing a large amount of heat.
Moreover, much work has been carried out into the study of coruscative materials (this concerns intermetallic combined materials, that is to say that, after having reached the reaction temperature, these products are capable of releasing large amounts of energy).
Mention may be made, for example, of:


______________________________________ Ignition Reaction Enthalpy % temperature temperature measured Material by weight (.degree.C.) (.degree.C.) (J.g.sup.-1) ______________________________________ Ti Sb Pb 48 23 29 570 1010 1045 Ti Te 27 73 433 870 815 ______________________________________
Patents WO 089/10340 and U.S. Pat. No. 4,830,931 relate to processes for the activations of metal surfaces in order to render them pyrophoric.
The basic principle is the attack on the metal surface by a mixture of a metal and of its chloride, at a temperature such that the substrate remains in the solid state and that the mixture is in the liquid state. The reaction is long, since it lasts several tens of hours.
The metal, thus covered with an intermetallic layer, is subsequently activated by a sodium hydroxide solution.
The metal which has become pyrophoric must then be stored in a liquid of low volatility (examples: fluoroethane, nonane, glycerol).
However, it is expensive to prepare these compounds and the latter can thus be exploited industrially only to a fairly limited extent.
Compounds which have formed the subject of other studies in this field are metal pairs which are in a position, when the reaction temperature is reached, to release relatively large amounts of energy with the formation of an

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