DE1421927A1 - Crystalline or glassy-crystalline material with a negative or very small coefficient of thermal expansion - Google Patents

Description

SIEMENS-SCHTOKGRIWERKE Erlangen., De & 5. Mar? 1060

. Aktiengesellschaft Werner-von-Siemens-Str.

PA 60/1197

Crystalline or glassy-crystalline material with negative or 3ehr. small coefficient of thermal expansion -

It is known that the tendency of glasses to devitrify at higher temperatures can be used to produce crystalline or vitreous-crystalline, ceramic-like materials. If a Q-las is kept at its devitrification temperature for some time, it is converted into a crystalline or glassy-crystalline state * Crystals appear here, which are able to form from the glass flip components during devitrification. Depending on the composition of the GKLases and the devitrification procedure, the end product can either be completely crystalline or still partially contain a glass phase. ! Such substances and processes for their production have been described, for example, in the German Auslegeschrift 1 045 056. It is also known to obtain weak ■ - ■ · ... ·. ';.' , '-. . - "- ι -Jj

142132? ■

positive thermal expansion coefficients of lithiura-containing ■ oleums, from which sick forms during devitrification of the 3 ■ spodumene (LipO.AlpQv, 45iOp), - whose thermal expansion is practically zero; Such a material is described in the German Auslegeschrift mentioned above, - It is also known that in ceramic compositions which lead to Idthiummirieral Eucryptite (Li ₂ O.Al ₂ Q, * 2SiO ₂ ) on fire, the thermal expansion is more negative can be set as with | 6-spodumene. '

The subject of the invention is a new crystalline or vitreous crystalline, ceramic-like material obtained from the glass phase, which is more comparable to previously known materials, in particular due to a negative or very small thermal expansion coefficient, high resistance to temperature changes and mechanical strength Kind of excellent Ί) βτ ^ material according to the invention, consists predominantly of β-Τ $ νϋ & τ $ φ1ίίϊ, as a Eiitglasüngs- _v product «. Particularly advantageous is the: material with a / S-eucryptite aiit .Iii ^ Q * ^ excess of up to ^ 10 wt .- ^, preferably of; 5 wt .- ^. For certain cases of end-use, a devitrification prodiict is favorable, in addition to the p-eucrypt, above all hagnesium titanate. consists. Further, it eats vorteilhelft, ate ^ -Eukryptit component "to be dimensioned -5C" .on at least 60 Qrew The material of the invention can be prepared in such a way "that the components of a p-eucryptite glass containing" preferably Li Q ₉ ttber ~

wird._ weft treatment by heat brought to devitrification to Biidung of Magnesiumtitanats in Entglasungsprodukt ß.en starting glass components MgO and TiO ₂ are added, namely E _t 5 to 10 Grew * - * ^ IiO _2, preferably 5 Crew.- #, and ^ i; i to SO MgQ, preferably 10 wt .- ^, Bie special execution aform d # e

Material according to the invention, -in the case of the ß-eucryptite
. Has a Ligö excess, builds on the plague position that the heat contract ion of the pure stoichiometric eucryptite can be significantly increased _{by the addition of excess Li 2} O, as can be seen from Table I below. In this the thermal expansion coefficient (Ot), the transformation (Tg) - * and softening points (Ep) are given for four samples with different lipo excess in the glass and deglazed state. while, at t200 ° C »

"'' - Table I ■ ■ '-' ■ '' -

. ". ·; - .. V." LigO surplus
Öew. ^ 64 '■ ": - .. ?? v- 10 ■ '.-' ■, · / f,; · '·
- '/,' V '■ · • ■ • ot _v io ^T * ° o
30-65O ⁰ O. 697 75 80 ' ^: "(jias .- ■;' - ,; ■ ■: 759 682 668 ir -'- ■ '. ■ -. "- ■ '-;' ■ .. ·. '
- ί -. '' -30 734 70ζ ' ■ * ■ :. ■ .--: · - ■■■ .- ■ Ä '-. Vi ^
■ ·. -Ά; "''" ·. "'■ - ··% - ■■? ■' ■ ■
irektglaiV ^: '· ■■.: ■
' ^k ** ". ''' $ '' '." ■ -'. '■ '"οι £ Ί« | Τα.γ- ^: "'
fio-800 ^ö 0 ; ^ 4 _; ;.;

ßi * T * bell · «iigt that the expansion coefficient

happy a1 $ t & -a

eur

«Ntgiaeten

^ "'" "ORIGINAL

■ temperature must be in the technical glass sense. In addition, the higher the temperature is measured, the faster full. the devitrification process is dragging on. On the other hand, the degree can; the devitrification also by measuring the treatment time with that. Temperature can be influenced. Both parameters, i.e. the treatment temperature and time, can influence the number and size of the crystals formed during devitrification and thus the mechanical, thermal and electrical properties of the material in a relatively wide range. Hours ^already;. The figures in Table I examples "the lower devitrification temperature at about 950 C * V / ählt.jnian is as * stated above, a treatment temperature of ⁰ C 12O0> Sun reaches aan in Jtih ₊ * E. a complete devitrification of the waste material ...

The above beschrieböne thermiBche Ausdehnurigsverhälten the recovered by, · \ devitrification ^ S-eucryptite with IiigO-tfberechuß is -erfindungsgemäß the formation of crystalline or gläeig-kriBtallineti "ceramic-like Mate Riet Lien with ntgeti ^ eifc ^ eiinaelwc / outdoor .i · small theimlachen Ausdehüungskoeffi zienteh exhausted.

Ea is known to add boric acid to glasses _; zu'use to improve the melting ability of the starting materials of the glass. Such additives: ·: The toughness of the melt is reduced at .higher temperatures and increased at lower temperatures ..; According to the invention> this is used to reduce the lower devitrification temperature considerably

a considerable advantage for the technical implementation of the devitrification process. At relatively low temperatures _t

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(Temperatures in the nail's softening point) the free mobility of the individual molecules is hindered and the formation of crystallization centers is promoted. Due to the increased toughness of the glass at low temperature, the linear crystallization rate is reduced. If the linear crystallization speed is low and the spontaneous crystallization capacity is high, the whole. Glass mass interspersed with tiny crystals; this is "of great importance for the homogeneity of the end product.

The finding that a TiO ₂ content greatly reduces the thermal contraction of the ρ-eucryptite with an Ii ₂ O excess, while the addition of MgO in the presence of TiO ₂ partially compensates for this effect is used. By "dimensioning the TiOp und.MgO additives, the thermal expansion behavior can be adjusted as desired within a certain range. Table II shows the thermal expansion coefficients (QC) for some materials of the aforementioned type.

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table II

ί ·
ITr. . ... .. ί .- .. ..1 ■ - - ² .-5 .-. . .. 4 ... [3rd, 6th 7th Bukryptite
(S). . Λ ■ 100 . .100 100 .100 Ίοό 100 100 Li ₂ 0-over-
shot (g) 10. - ■ -. .- '[3;' ■ ' * 5. .; _5
,· .1 TiO ₂ / (sj; - ■■ ..-. - ■ δ 5 . '■ .10, · . ·: -5, ],. ... 5, 10 .; 5 MgO (g) _. 5 15th 20th 10 10 5 } 5. Applied. ':
temperature
for devitrification
(1 hour) ( ⁰ O) -. 1200 1200 1000 100Ö 1200: ^ν ϊοοο 11! OO I.
• H "- · ■■■
Ή
S ■ - ■ 20-X ⁰ C
Al
ω W) o "
Λ ti o
03 ti C- -..- · ■
a »-p2 20-80O ⁰ C
U ti ö
(D 01 (D .j • 600 °
-24 »
400 °
0 -320 °
7th - 22Ό ^Ο
5 .--. · ... 5 ' - ^u ■ .. 26; . 21 .. * V ^ V--
.36

The samples No. 2, 3 and 4 show that it. mögli.ch is in the invention. Material to achieve a practically vanishing or quartz-like coefficient of thermal expansion over a range of a few 100 ° C. This is the case with the use of ceramic bodies in many areas. ; . of technology, especially when they are exposed to extreme thermal shock loads. This _; -

80981271) 300

. Behavior is advantageous, for example, when ceramic parts with metal parts should be connected. For example, with the material according to the invention, it is possible to use a current feedthrough To shrink or solder a metallic threaded ring from a material according to sample no. 2 without doing so there is a risk of cracking. These properties open up numerous application possibilities for the material according to the invention in technology, e.g. in electrical engineering as. ceramic insulator, post, rod insulator, for tube parts and the like. For many of these uses it is the material according to the invention the 'known electrical porcelain think.

In addition to the adaptability of the expansion coefficient, as already mentioned above, the mechanical and thermal properties of the material according to the invention are particularly noteworthy, in particular its great hardness, which is e.g. comparable to agate, its extremely high flexural strength, tensile strength and abrasion resistance. This results in further applications of the material according to the invention, in which ' 9b * these; apeal properties · .arrommti, eg. as. , WÄrkeiöff iXü * / noöh ^ devices, such as

Turbines, internal combustion engines and the like. ·

.8 claims

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Claims (5)

Claims' 1.) Crystalline or glassy-crystalline, more ceramic-like Material with negative or very small thermal vision Expansion coefficient, characterized in that it consists mainly of A-eucryptite as a devitrification product. 2 »Material according to claim 1, characterized. that the £ j-eucryptite contains a LipO excess of up to 10% by weight, preferably of 5% by weight. / " _t 3 · Material according to claim 1 or 2, characterized in that the devitrification product in addition to the jß-eucryptite above all consists of magnesium titanate. . 4, · Material according to claim 1, 2 or 3 »characterized by that it contains at least 60% by weight / 3 eucryptite. 5. Process for producing the material according to one of the preceding claims, characterized in that a the components of the / o -eucryptite-containing glass, preferably with excess LigO, by heat treatment to remove ' glazing is brought. . . . 6. The method according to claim 5, characterized in that a glass is used which, in addition to the components of desp * eucryptite Admixture ta. of MgO, TiO «and / or BpO- contains. - 8 - sheets / pa 809812/0300 7. The method according to claim 6, characterized in that a glass containing the components of the / ij-eucryptite is assumed is with a TiOp content of 0.5 to 10 wt .-? £., preferably from 5.Gew * - ^, an MgO content of 1 to 20 Weight-5%, preferably of 10% by weight, and / or an SpO, content from 1 to 8% by weight, preferably from 4% by weight. 8. Application of the material according to one of claims 1 to 4 » • in which it is due to its high thermal shock resistance and / or its great hardness, extraordinarily high bending '" Break, tensile and / or abrasion resistance matters. . . 809 812/0300