Metal treatment – Stock – Amorphous – i.e. – glassy
Reexamination Certificate
2000-04-18
2003-07-08
Wyszomierski, George (Department: 1742)
Metal treatment
Stock
Amorphous, i.e., glassy
C428S650000, C374S032000, C374S179000
Reexamination Certificate
active
06589370
ABSTRACT:
This invention relates to the use of quasi-crystalline alloys for the absorption of infra-red radiation as well as devices for the absorption of infra-red radiation comprising an element made of a quasi-crystalline alloy.
Various types of devices are known that absorb infra-red radiation. In particular, devices are known that carry out the photo-thermal conversion of the infra-red radiation, in which the absorbed light energy is converted into heat. These are notably solar radiation collectors which include a layer of a paint that absorbs the infra-red radiation, deposited on a substrate. Among these devices, one may mention, in particular, collectors with a heat exchange medium or the Trombe wall. In these devices, the heat is taken from the absorbent medium through the substrate, assumed to be a good thermal conductor, by a heat exchange fluid, from which the collected energy is extracted. In general, said paints are made up of organic materials containing absorbent pigments or metal powders which are very finely divided and bonded by an organic additive. Metals can only be used in a very finely divided state, or possibly in the form of a massive element having a very high surface roughness since they are strongly reflecting in the massive state and smooth. However such materials show a poor resistance to external attack and are damaged by mechanical scratching, wear or corrosion. Because of this, they must be protected against attack, for example by glass screens, which increases the price and decreases the durability of them. Furthermore, the interface formed between the absorbing paint and its substrate plays a decisive role in the flow of heat transmitted to the heat exchange fluid and in the life span of the device. Devices are also known in which the infra-red radiation is converted into electrical signals. Among these devices, one may mention bolometers, in which the infra-red radiation causes a variation in the resistance of metallic or semi-conductor elements. The material used for the absorption of the infra-red radiation must have a high electrical resistivity, a high temperature coefficient and a low thermal conductance.
One can also mention, thermal probes (thermocouples) in which the e.m.f. of a pair of conductors of a different kind is measured.
For all these types of infra-red radiation sensors used as detectors, it is necessary to have a low dark current, which means that they are often placed inside a cooled enclosure intended to reduce thermal excitation in the materials and to reduce the flow of ambient radiation.
Furthermore, quasi-crystalline alloys are known, which are alloys made up of one or more quasi-crystalline phases. By quasi-crystalline phase, one understands a quasi-crystalline phase in the strict sense or a phase that approximates to one. A quasi-crystalline phase in the strict sense is a phase that has a symmetry of rotation normally incompatible with the symmetry of translation, that is to say a rotation axis symmetry of order 5, 8, 10 or 12, these symmetries being revealed by the diffraction of the radiation. By way of example, one can mention the icosahedric phase of point group m3 5 and the decagonal phase of a point group 10/mmm. An approximating phase or an approximating compound is a true crystal to the extent that its crystallographic structure remains compatible with the symmetry of translation, but which has, in the electron diffraction image, diffraction diagrams the symmetry of which is close to rotation axes 5, 8, 10 or 12. By way of example, one can mention the orthorhombic phase O
1
, characteristic of an alloy having the atomic composition Al
65
Cu
20
Fe
10
Cr
5
, the lattice parameters of which are: a
0
(1)
=2.366, b
0
(1)
=1.267, c
0
(1)
=3.252 in nanometers. This orthorhombic phase O
1
is said to be approximate to the decagonal phase. Furthermore, it is so close that it is not possible to distinguish its X-ray diffraction diagram from that of the decagonal phase. One can also mention the rhombohedric phase with parameters a
R
=3.208 nm, &agr;=36°, shown in alloys of composition close to Al
64
Cu
24
Fe
12
in its number of atoms. This phase is a phase that approximates to the icosahedric phase. One can also mention the orthorhombic phases O
2
and O
3
with respective parameters a
0
(2)
=3.83; b
0
(2)
=0.41; c
0
(2)
=5.26 and a
0
(3)
=3.25; b
0
(3)
=0.41; c
0
(3)
=9.8 in nanometers which is formed in the alloy of composition Al
63
Cu
8
Fe
12
Cr
12
in its number of atoms. One can further mention a phase C, of cubic structure, very often observed in coexistence with the approximating phases or true quasi-crystalline phases. This phase which is formed in certain Al—Cu—Fe and Al—Cu—Fe—Cr alloys, consists of a superlattice, through a chemical ordering effect of the alloy elements in relation to the aluminum sites, of a phase with a CsCl structure and a lattice parameter a
1
=0.297 nm. One can also mention an H phase of hexagonal structure which derives directly from the C phase as the epitaxy relationships, as observed by electron microscopy demonstrate, between crystals of the C and H phases and the simple relationships which link the parameters of the crystal lattices, namely a
H
=32a
1
3 (roughly 4.5%) and c
H
=33a
1
/2 (roughly 2.5%). This phase is isotypical of a hexagonal phase, designated &PHgr;AlMn, discovered in Al—Mn alloys containing 40% by weight of Mn. The cubic phase, its superlattices and the phases which derive from it, constitute a class of phases approximating to quasi-crystalline phases of neighboring composition. For more information about quasi-crystalline phases in the strict sense and phases approximating to them, reference can be made to EP-A-0 521 138 (J. M. Dubois, P. Cathonnet).
The quasi-crystalline alloys generally have good mechanical properties, high thermal stability and good resistance to corrosion.
The present inventors have now found that the rate of absorption of infra-red radiation of these quasi-crystalline alloys is particularly high and that they could be advantageously used in devices intended to absorb infra-red radiation.
Consequently, the objective of this invention is the use of quasi-crystalline alloys for the absorption of the infra-red radiation, and a device that absorbs the infra-red radiation, which includes an element made of a quasi-crystalline alloy.
A device according to this invention, that absorbs the infra-red radiation, is characterized in that it comprises as a coupler element for the infra-red radiation, an element made of a quasi-crystalline alloy made up of one or more quasi-crystalline phases representing at least 40% by volume of quasi-crystalline alloy, a quasi-crystalline phase being either a quasi-crystalline phase in the strict sense which has symmetries of rotation normally incompatible with the symmetry of translation, that is to say rotation axis symmetries of order 5, 8, 10 and 12, or an approximating phase or an approximating compound which is a true crystal the crystallographic structure of which remains compatible with the symmetry of translation, but which has, in the electron diffraction image, diffraction diagrams the symmetry of which is close to rotation axes 5, 8, 10 or 12.
A particularly preferred quasi-crystalline alloy is an alloy in which the quasi-crystalline phase is an icosahedric phase of point group m3 5 or a decagonal phase of the point group 10/mmm.
The quasi-crystalline alloys in which the quasi-crystalline phases represent at least 80% by volume are particularly preferred.
Among the quasi-crystalline alloys which can be used for the devices of this invention, one can mention those which show one of the following nominal compositions, which are given as an atomic percentage:
Al
a
Cu
b
Fe
c
X
d
Y
e
I
g
, (I) in which X represents at least one element chosen from among B, C, P, S, Ge and Si, Y represents at least one element chosen from among V, Mo, Ti, Zr, Nb, Cr, Mn, Ru, Rh, Ni, Mg, W, Hf, Ta and the rare earths and I represents the unav
Dubois Jean-Marie
Machizaud Francis
Centre National de la Recherche Scientifique
Wyszomierski George
LandOfFree
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