DE1287763B - - Google Patents

Description

ϊ 287 763
1 2

This invention relates to a method of causing physical decomposition when so treated with glass-ceramic articles, however this tendency can either have modified properties. In particular, it concerns the production of solidified glass objects, which have been completely overcome or very strongly in glass-ceramic materials, which have a structure in which the structure of well-developed glass-ceramic objects, which has a fine-grained surface layer that is characteristic of pressure-sensitive ceramic materials, is reduced . On the basis of this chemical composition within the discoveries, it is possible to produce an object from the crystal phase by means of an ion exchange changed to a glass-ceramic material of a given composition, and by subsequent chemical treatment within a surface layer as glass, which Then a glass-ceramic material of moderate continuous devitrification is subjected to a phase separation of different chemical composition and is subjected to a fine crystalline structure with different physical properties to develop within a vitreous matrix by an equal of the object The material produced in this way has physical properties of its own to a considerable extent, which are essentially different from those produced by an ion exchange, that of that of the stem glasses s and are more similar to those that result from a thermochemical treatment, solidified conventional crystalline ceramic material can be solidified. Oddly enough, this is a reference. The characteristic strength of a ceramic material, which is limited and can be used alone, is often greater than that of ao on certain crystals or crystal structures. To stem glass material; Usually one observed example, it was found that a glass ceramic which contains an increase in strength after abrasion of only one metastable / 3-eucryptite crystal phase does not 352 kg / cm ² in the glass material to 703 to 844 kg / cm ² due to such an ion exchange solidified in the corresponding glass-ceramic material. However, it is often desirable to increase this inherent strength even further. This is especially true for / 5-spodumene form is easily solidified. Objects that are hard hit have also been found to have other glass-ceramic counterparts. Kitchen utensils, and for such items, would stand in a manner similar to the / 9-spodumen which occasionally exposed to heavy loads may solidify glass-ceramic items. If these objects are thermally stable, it is known to increase the mechanical strength of a / S-eucryptite, nepheline, carnegieite or glass object by having a "filled" ß-quartz crystal phase, the object is under compressive stress. The term »ß-Spodumene« was developed for the designation surface layer. This is usually used by means of a crystal belonging to the trapezoid, a relatively thin layer that extends evenly over the 35 radical group of the tetragonal system, the surface of the object and printing the formula Li ₂ O · Al ₂ O ₃ · 4 SiO ₂ has and has a high voltage, which is compensated for by stresses in the temperature form of oc-spodumene, from wel inside the object. Until now, rather than by heating to a transformation, such solidification is usually obtained by a temperature of about 700 ° C. Likewise, heat treatment achieved, which is referred to as tempering 40, the expression "β-eucryptite" is used to denote and in which the surface of a vitreous body of a crystal in the trapezoidal group of the hexagonal system suddenly cooled from an elevated temperature is used, which becomes the formula. Recently, chemical strengthening Li ₂ O _{· Al 2} O ₃ · 2 SiO ₂ and a high temperature process have been known in which compressive stress is in the form of -Eucryptite. In lithium aluminum silicate of a surface layer of a glass body or glass ceramic material, however, the crystal object developed by ion exchange does not strictly correspond to one of the naturally occurring ones. Crystal phases. Rather, they are in the form of glasses and crystalline ceramics are such a peculiar solution that generally has the formula and _{corresponds to Li 2} O-Al ₂ O ₃ -HSiO ₂ , which is so fundamentally different from one another, in which "κ" is between materials that any correlation in behavior 50 can vary 2 and 7 or more, in dependence or in properties is normally not dependent on the silica content of the parent. The various chemical and thermo glasses. There is evidence that chemical treatments applied to glass objects, ions such as magnesium, appear in the crystal phase are usually crystalline ones if they are present in the glass. Ceramics ineffective or show on these two 55 However, without exception, X-ray diffraction shows very different effects on materials. Likewise a crystal of the trapezoidal group either have the method for thermal treatment of in the hexagonal or tetragonal system. Therefore glasses are normally no counterpart in the case of the identification of glass-ceramics crystalline materials because of the clear sub-usual, such lithium aluminum silicate crystal phases, differ in the physical properties and the 60 those to the trapezoidal group of the hexagonal structure. Systems belong, as / 3-eucryptite crystal phases, and it has now been found, quite surprisingly, that those belonging to the trapezoidal class of the tetra between a material belonging to a vitreous system as a ß-spodumene crystal ceramic object is in contact , and to designate the phases. This notation is used here as well, when the crystals contained therein are exchanged.

den can so that the crystal phase within the If the stoichiometric oxide ratio in the

Subject is chemically changed in situ. Her crystals is such that the coefficient "" tends between 2 common sintered ceramic objects and about 3.5 in the formula Li ₂ O-Al ₂ O ₃ -WSiO ₂

1287 733

3 4

is usually a stable / i-eucryptite publication No. 1309 by the Geophysical Laboratory

Crystal phase observed. For larger shares of with the title "Nepheline Solid Solutions").

SiO ₂ (»« «greater than about 3.5) develops. The situation is in glass-ceramic technology

ß-Eucryptite crystal of metastable nature, initially similar. Here, too, the term "nepheline" is used

borrowed at temperatures of around 800 ° C. This 5 denotes a fairly broad range

transforms into a / 9-Spodument type crystal from solid solution crystal phases which

around, if at even higher temperatures in the characteristics that correspond to those of the mineral.

Heat-treated in the order of 900 to 1150 ^° C. The crystals can vary in their composition

will. vary considerably, but are substantial

The expression "/? - quartz" was used to denote sodium or sodium potassium aluminum silicate, a hexagonal trapezoidal form of SiO ₂ crystals in the hexagonal system and which ^{is stable between 573 and 87O 0} C and has a common X-ray diffraction pattern in the also a slightly negative heat x-ray analysis. So while every nepheline crystal shows expansion coefficients and, due to a very small one, a characteristic pattern, the Ab birefringence can be characterized. It is known that the levels and intensities of the maxima vary somewhat depending on the nature of the crystal phase, and that this crystal and that known as / 3-eucryptite.
(Li ₂ O · Al ₂ O ₃ · 2 SiO ₂ ) form a complete set of of particular interest in the context of solid solutions. These solid solutions were addressed to the present problem of glass-ceramic verdening by Bürger in his essay "The Stuffed Fortification is a Family or System of Nepheline Derivatives of the Silica Structures", Am. Mineral., 20 solid solutions-crystal phases, which in their chemi-39, 600-14 (1954), referred to as "filled derivatives" (see stuffed composition generally of the formula derivatives) of /? - quartz. The author Na ₈ - ^ K _x Al ₈ Si ₈ O ₃₂ corresponds, in which χ from 0 ascribes a structure to these solid solutions that can fluctuate up to about 4.73. It has been observed that some of the tetrahedral silicon ions in glass-ceramics of the nepheline type replace the normal / 3-quartz with aluminum ions, and different ions, and in particular the alkali metal, tend to "fill up" the electrical charge caused by cations in the crystal phase Space vacancies in the SiO ₂ - borrowed in the same proportions to he double helix is balanced with lithium ions. seem like in the stem glass composition.

Since that time it has been known that other ions, too, maintain a greater proportion of them

like the magnesium ion, either alone or in combinations.

bond with the lithium ion in the SiO ₂ structure licher crystal type, namely kalsilite, which is the original

Can be "filled up". For example, in the initial crystal phase in the glass ceramic too

a publication by W. Schreyer and form.

J. R. Schai r e r, “Metastable Solid Solutions with In this family of glass ceramics, the

Quartz-Type Structures on the Join SiO ₂ —MgAl ₂ O ₄ *, 35 crystal phase arranged according to the same scheme

Geophys. Lab. Paper No. 1357 (1961), that it is shown that by D ο η η a y and co-workers on

a number of metastable solid solutions of the mineral nepheline have been applied. Under

ß-quartz can also be used in the connecting chain _{SiO 2 —MgAl 2} O ₄ referring to the formula Na ₈ ~ _x K ₃ Al ₈ Si ₈ O ₃₂

can be formed. In this case, the replacement of the nepheline crystal is as provided in the following forms-

of aluminum against silicon can be viewed by a magnesium 40 lying:

Filling of the / S-quartz interspace _{voids accompanying- ΛΛ1} . _rt ",

tet. When 2 AP + is replaced by 2 Si ⁴ +, there is a low potassium content, with χ ranging from 0.0 to 0.25;

this case, only a magnesium ² + ion necessary with moderate potassium content, wherein χ 0.25

while in the case of / 3-eucryptite 2 Li + ions not- extend to 2.0;

are agile _ 45 rich in potassium, with χ ranging from 2.0 to 4.73.

In a well-known group of see-through

The term "Carnegieite" is used to denote the predominantly / 3 quartz crystal phase of a crystal that consisted of the general formula consisting of Mg ++ with or without Li ⁺ or Zn ++ - Na ₂ O · Al ₂ O ₃ · 2 SiO ₂ and a certain crystal ions were "filled up". Based on the pre-50 geometry. It has now been found that the mineral terminology discussed below can be used to manufacture these ceramic materials, glass-ceramic materials as "filled" / 2-quartz - which contain a primary crystal phase, which is recognized in glass ceramics. their X-ray diffraction pattern to the crystal

It is true that not all "filled" ß-quartz glass Carnegieite corresponds. Using the crystal pattern ceramics transparent, however, the terminology used for such glass-ceramic materials becomes transparent Terminals used in glass ceramics and their crystal phases are also named logic is also used here and is covered with »Carnegieit« on all glass ceramics.

extended, which is a corresponding "padded" usually when glasses that are essentially

Have crystal structure. from considerable amounts of Na ₂ O · Al ₂ O ₃ and

The term »nepheline« is used to denote 60 SiO ₂ composed, with the help of crystals of a natural mineral, which is crystallized into a crystal structure belonging to the germination with the formation of glass-ceramic materials hexagonal crystal system, the primary crystal phase, which has and is defined by the chemical formula ( Na, K) AlSiO ₄ is deposited, a nepheline crystal phase is characterized from. However, it was pointed out by D ο η η ey crystals, which correspond to the patterns of the nepheline crystal and co-workers, that the mineral 65 corresponds. However, in a limited nepheline, in a wide range of solid solutions, there may be a composition range and in the absence of one, the limits of which are not even precisely specified even by the above nucleating agent, a so-called self-nucleating formula (Ver Carnegieite crystal phase by suitable heat-

5 6

Treatment of material containing Na ₂ O — Al ₂ O ₃ —SiO ₂ glasses, ie an ion that is wrapped inside. half a glass body migrate or diffuse The invention relates to a method for ver can, sufficiently long with a glass-ceramic solidify a glass-ceramic object that brings a surface into contact to have an exchange parent crystal phase, which has an exchangeable 5 between an exchangeable ion from the crystal - contains alkali metal ion and ß-spodumene, thermal phase of the glass ceramic material and the ausstabiler / S-eucryptite, nepheline, carnegieite or /? - quartz exchangeable ion from the contact material is to be effected, this method being characterized by this. The extent and depth of the exchange is to keep the surface of the object in contact with a material which is an ion io of time, according to the principles of diffusion. In general, a temperature of larger ion diameter than the alkali metal - at least 200 ° C is required in order to contain a nominal dimension of the parent crystal phase, which are mutually beneficial exchange and are generally exchangeable for this larger ion and that, depending on the relevant material, alkali metal ion within a surface layer to exchange higher temperatures to achieve the solidification of the object and pressure 15 is required.

to relieve tension in this surface layer. The speed of exchange increases with it

wrap. the temperature so that it is desirable at

An exchangeable ion is a positive or as high a temperature to work as it is prak-metal ion, d. H. one of the alkali metal ions, which is possible on a table to save time. Theoretically is is able, within a glassy medium 20, the upper temperature limit that at which to migrate or diffuse and melt or deform through a crystal structure, other wandering ion to be replaced. To switch off tension. In practice, however Movement and the exchange of ions can be caused by other factors, in particular by are through the joint action of a marriage- the question of the presence of a salt material, mix force, in this case the difference in 25 which has a suitable melting temperature and the ion concentration between the glass ceramics is relatively inert, much lower temperature mixing and the contact material and one boundaries enforced.

physical force, which heat and / or a The speed of ion exchange and

electrical potential can be. The movement thus takes place in the development of hardening pressure normally held until the effective 30 tensions fluctuates with and depends on the Force is removed or an equilibrium condition special type of the glass-ceramic in question is achieved. Such an exchange is in the material. The speed of the outermost surface the degree of exchange is very high ion exchange and the solidification of the and decreases too steadily towards the inside. Size of the ion which is exchanged, as well as

The ion exchange can be detected 35 from the conditions of the exchange. For example by a change in chemical analysis, is the exchange rate between potassium x-ray diffraction and work considerably through physical intrinsic or cesium ions and lithium ions. This shows less after an ion exchange than between sodium and lithium ions. X-ray diffraction patterns often all character- As a result, stronger exchange conditions are ristic maxima of the original crystal phase, 40 d. H. longer duration and / or higher temperature which, however, in terms of their location and intensity, are easily lost in the first-mentioned exchange are pushed. This indicates that a comparable degree of exchange and deformation, however, no destruction of the original consolidation can be achieved. Although also alkali metal Crystal building cell is present. In some cases, ions larger than sodium and potassium, however, if a new pattern of refractive 45 can be interchanged, it is common maxima that a real crystal remodeling takes place. inexpedient to use such ions because of

In practicing the present invention, the low exchange speed and the becomes a glass-ceramic article, which is an extremely high cost suitable material for Ausder specified crystal phases with an exchange purpose. As mentioned earlier, takes contains baren ion, prepared in a known manner. 5 ° in each case the extent of the ion exchange In general, such glass-ceramic dimensions and the solidification with the temperature and / or materials produced by first considering the time. However, it has been found that the a suitable glass composition melts and a certain material achievable strength and thereafter the formed object gradually increases up to a maximum value and Subjected to heat treatment, by which the design then essentially retains this value, without development of a knock phase in the whole material consideration of further ion exchange, is triggered. Compositions are known, unless otherwise specified in this invention

which nucleate in themselves, but it is, is the strength of a certain object In general, a special core or material called "strength" is necessary Formative mean of the original glass composite 60 after abrasion in a tumbler "given as modulus of rupture. Adding settlement and heat treatment in that is a measure of the flexural strength of a one perform two stages, the first of which is the test piece subjected to abrasion, e.g. B. a staff Stage is the core-forming stage. or a rod of known cross-section, and

In its broadest scope, this relates to this measure being determined in a conventional manner. Invention the synthesis of a chemically modified 65 It is called "strength after abrasion in the tumbler" crystalline phase referred to by ion exchange within because the test pieces, usually zylineines glass ceramic body. This can be achieved by using three rods 10 cm long and 0.6 cm through be that you have a replaceable ion knife, before the strength measurement of a hard one

Be subjected to abrasion treatment. Evidence between 700 and 800 ⁰ C is to be used. We know that all objects when they are used at temperatures above 800 ° C are subject to a certain degree of abrasion and that every change between the crystal phases of the practical strength measurement takes this factor into account surface layer of the object, whose ions must be considered. 5 were exchanged. As a result, the

In the Taumier abrasion test, ten cylinder-strengthening effects of the ion exchange are lost, three test pieces with 200 cm ^{3 of} silicon carbide par- which is why the upper limit for the treatment temperature particles with a diameter of up to 0.6 mm must be considered to be 800 ° C,
mixes and 15 minutes in a No. 0 ball mill- To achieve temperatures up to about 600 ° C,

vessel of a tumbling motion at 90 to io, a potassium nitrate bath (KNO ₃ ) can be used, subjected to 100 rpm. Control tests, however, have shown that this salt tends to degrade fairly quickly with this tumbling abrasion treatment and that both the glass-ceramic and the surface defects achieved are similar to those which are encountered in the operating devices at higher temperatures with severe abrasion and when the counter-attack is hit. Chlorides are also normally strong during use, e.g. B. as cooking 15 corrosive, especially at elevated temperature dishes, actually occur. doors, however, is a mixture of chloride and

After the cylindrical test pieces of tumbling sulfate of potassium were relatively inert and therefore subjected to abrasion treatment, breaking and solidifying purposes became particularly suitable. This load was determined for each test piece by the fact that the mixture forms a eutectic at about 52% KCl that the piece can be cut between two knife edges _{at a distance of about 20 and 48% K 2} SO ₄ with a melting point of about 690 ° C the composition of the bath is applied, a second pair of knife _{edges can be varied in the range from about 50 to 60 ° / 0} KCl and 40 to evenly selected distance between the first 50% K ₂ SO ₄ , but the two knife edges are mounted on the test piece given eutectic mixture loads the most general and the second pair until bending fracture occurs. 25 usable.

The modulus of rupture of the test piece is then measured at a very satisfactory level of consolidation.

Consideration of the load, size and movement can be achieved by calculating the Na shape of the sample and the geometric test trium against lithium ions in 1/3 spodumene conditions in kg / cm ² and replacing the material, but the solidification achieved represents the highest tensile stress that can be quickly lost on the surface 30 when the object of the test piece is created against the stress. brought to elevated temperatures for a long time

The invention is further contemplated or used at these temperatures. if the conditions of the solidification treatment. B. a / 2-spodumene glass ceramic object wrote that they are particularly effective in each species by exchanging sodium for lithium ions are made of glass-ceramic material. 35 solidified and then a continuous heat

Go / 3-eucryptite about _^2/3 of strength increase contains a glass-ceramic material which is either a treatment is subjected at about 400 ⁰ C, 3-spodumene or a thermally stable / within about crystal phase, can be easily characterized solidifies 100 hours lost again . As a result, there will be limited opportunities for the article to have a sodium application when the counter-molten salt bath is immersed, preferably at a 40 stand in this way.
Temperature above 45O ⁰ C. To achieve an optimum Although it is difficult Grind a corresponding strength, the article in the bath upstream fortification by an exchange of potassium to preferably at a bath temperature of 500 to 600 ° C to obtain lithium ion, but when which is reached for a period of about 4 hours down to a decrease in strength, it is held for a few minutes. However, a corresponding 45 longer times at temperatures can keep up beisprechende to 600 ⁰ C solidification at lower temperature range. As a result, one after this Verratur can be obtained by increasing the duration of the driving solidified object at temperatures treatment. For example, in a ß-spodumene material about 200 ° higher can be used an optimal strength by than the maximum temperatures for a similar treatment in a sodium salt bath for 30 Mi- 50 object, which by an exchange of grooves at 575 ° C or for 2 hours at 525 ° C sodium has been solidified against lithium ions. be achieved. In the case of / 3-eucryptite materials, it is considerably expedient to use a salt bath of 585 to 59O ⁰ C to the field of application for ion exchange; at this temperature becomes the optimal solidified glass-ceramic materials.
Strength achieved in about 10 to 20 minutes. In order to achieve these temperatures, it is useful, unusual in that such a glass-ceramic, to use a sodium nitrate bath, preferably an object by a conventional ionization with the addition of about 15% sodium sulfate. exchange treatment in a molten sodium

The corresponding exchange of potassium for salt bath is not solidified if it is only lithium-lithium ions can be effected in such a way that one contains 60 ions which were introduced into the crystal during the original formation of the glass-ceramic object in a molten crystal. Potassium salt bath immersed for intimate contact. However, such a glass-ceramic object can cause the potassium ions in the salt bath and the surface of the glass-ceramic object to be exchanged for lithium ions in a potassium salt bath. To consolidate an ion exchange in useful 65. In this case, both the extent between potassium and lithium ions in the salt bath and the treatment conditions to achieve those appropriate time, it is generally necessary for the exchange treatment of temperatures above 55O ⁰ C and preferred potassium versus lithium ions at a time ß-spodumene

909 504/1523

9 10

glass-ceramic object have been described. In the development of a nepheline crystal phase, an optimal solidification is generally achieved, which in its composition ^{corresponds to a potassium temperature between 700 and 800 0} C in a period of time, is achieved from 4 to 6 hours. the glass ceramic usually lighter or faster

In contrast, an object that solidifies a 5 than a nepheling glass ceramic with less / J-quartz crystal phase has potassium content through ion exchange. For example, a nepheline requires an introducer Lithium ions contain, through a Na- glass ceramic, the potassium content of which is low in potassium trium for lithium exchange or a potassium crystal form corresponds to an ion exchange be further solidified against lithium exchange. relatively higher temperatures or during a The manufacture of such /? - quartz objects after a longer period of time in order to achieve an increase in strength to achieve an exchange of lithium for magnesium abrasion. In addition, the achievable ions is maximum strength in the low-potassium mades in a concurrent invention by the same inventor. materials under optimal treatment conditions

According to the doctrine, these concurrently running are considerably lower than the potassium-rich ones Invention can be "filled" ß-quartz glass ceramic materials. The potassium-rich area appears to be optimistic undergo an ion exchange, which offers opportunities for solidification chem magnesium ions from the crystal phase and thus indicates possible partial changes-lithium ions within a surface layer of the stanchion in the compound object, which is moderately rich in potassium replaced, whereby compressive stresses subsidence.

are developed and the strength of the counterpart is increased. Due to this type of ion - thus the composition and nature of the exchange, especially if the same at temperature - originally developed nepheline crystal phase depends. temperatures is performed over 800 ⁰ C, a This can be controlled by that one useful degree of solidification are achieved. However, at such a relatively high temperature it provides enough potassium ions together, so that the molten lithium salts used in the crystal phase develop a desired shape of the material to be treated and the operating nepheline crystals during the Auseituren. According to the directions above. given formulations regarding the ions

This problem can be alleviated by the ratio of potassium to sodium ions in that the replacement of the lithium ions for the 30-ion based in the nepheline crystal phase at least magnesium ions at temperatures below 800 ⁰ C 1:31 (0.25 to 7.75) and preferably above 1: 4. In this case, however, the achievable extent of solidification can be achieved if the exchange is achieved after abrasion at temperatures between 400 and an appropriate period of time, ie up to about 600 ^° C. within 24 hours, but 16 hours, relatively low. For example, higher temperatures can also be used, an increase of about 842 kg / cm ² in one de, in order to increase the rate of exchange to 16 hours of treatment at a salt bath temperature and also the extent of achieved in a certain of 775 ° C. Time to improve the solidification achievable.

A very significant increase in strength The conditions for optimal consolidation in

this glass-ceramic object of the Carnegieite type, which is subjected to a lithium ion exchange, can now resemble those which have just been achieved for objects of the sodium nepheline type. Thus, in both or potassium ions, the lithium ions introduced in the first exchange type of glass-ceramic objects are exchanged. male strength in usually less than 16 stun The same strengthening effect is achieved in the jS-quartz 45 by observing the object in a materials, in which the lithium ion mixed KCl K ₂ SO ₄ -Salzbad of 700 to 800 ⁰ C. is introduced at temperatures above 800 ^0C. However, turns up. The following examples further explain it, if it is of considerable importance in the treatment of the practical implementation of the invention and of materials into which the lithium ion was introduced at lower temperatures and which can be achieved thereby
usually difficult with a single treatment

are to be solidified to a sufficient extent. Preferred example 1

wise, each of the individual ion exchange treatments

lungs at temperatures between 750 and 800 ⁰ C Raw materials were mixed and melted

carried out, with optimal solidifications in about 55 zen, which are achieved to a glass of the following oxide together-4 to 16 hours. settlement led (weight percentage basis): SiO ₂ 69.7%,

A glass ceramic object of the nepheline type Na ₂ O 0.3%, K ₂ O 0.1%, Li ₂ O 2.6%, MgO 2.8%, is solidified by the fact that a monovalent ion, Al ₂ O ₃ 17, 9%, ZnO 1.0%, TiO ₂ 4.8% and As ₂ O ₃ which is greater than sodium, preferably 0.9%. The glass was drawn into rods of 0.6 cm diameter potassium ion, against the sodium ion of the nepheline knife, which is exchanged to lengths of 10 cm ge crystal phase. The achievable excerpts were. These glass samples became too solid and the ease with which glass-ceramic samples of the /? - Spodument type is achieved by this method, heat treatment according to the following scheme depends on the composition. Specifically converted: heating at 300 ° C / hour to make the presence of a substantial amount of 65 750 ⁰ C; Heating at 100 ° C / hour to 850 ⁰ C; Potassium in the Nephelinstammkristall the same for heating at 300 ° C / hour to 1080 ⁰ C; 2 hours this type of consolidation is more suitable. held at 1080 ⁰ C. Rapid cooling to room

If there is enough K ₂ O to remove the temperature.

These glass-ceramic samples were then divided into groups of six for ion exchange treatment in a molten salt bath consisting of 85% NaNO ₃ and 15% Na ₂ SO ₄ . Each group of samples was immersed in the salt bath and treated according to an individual time-temperature scheme. After removing from the bath and cleaning, each ion-exchanged sample was subjected to tumbling abrasion and its characteristic modulus of rupture determined as described above.

Several groups of samples were treated for different times at 525 ° C. in order to determine the influence of the treatment time on the consolidation. The following table shows the modulus of rupture (in kg / cm ² IO ³ ) and the corresponding treatment time:

Time

0 minutes

15 minutes
30 minutes

1 hour .

2 hours
4 hours

16 hours

Average modulus of rupture ^ao

0.842

1.27

2.35

3.01

5.04

5.50

5.59

A few more groups of glass samples were treated for 30 minutes at different temperatures, to demonstrate the influence of temperature on the achievable consolidation. The following The table shows the values obtained, compared with the table above the time is replaced by the temperature:

temperature

475 ° C 1.34

500 ° C 1.94

5 ^° C 2.35

55O ⁰ C 4.67

Average modulus of rupture

45

B e i s ρ i e 1 2

To demonstrate the practical advantages of the invention, a group of eighteen 2.5-1 filter nozzle blown from the glass from Example 1 and then according to heat treatment converted into the glass-ceramic state according to the scheme described in this example. the Nozzles were identical, as far as the manufacturing tolerances allowed.

A group of six nozzles were set aside as a reference standard. A second group of twelve nozzles was immersed in the molten salt bath of Example 1 for 3 hours at a temperature of 475 ° C, this scheme was chosen to avoid possible chemical attack of the Avoid salt material on the glass ceramic surface. Both groups of nozzles were then evenly on the surface opposite the surface used in the subsequent impact test sanded off. This abrasion was carried out so that the surface was under uniform Time and pressure conditions with sandpaper (grain size up to 0.1 mm in diameter) rubbed.

After abrasion, each nozzle was mounted in an impact test apparatus and successively Subjected to blows of increasing strength until breakage occurred. The device contained a mit Press plates encased a block on which the nozzle was firmly seated, and a ball impact hammer made of plastic, which was attached to the end of a pendulum arm. Each nozzle was identical mounted so that the blow on the wall of the nozzle along a line of highest diameter took place. The impact energy required for breaking was for the untreated nozzles 0.036 meter kilograms and 0.268 meter kilograms for the solidified nozzles.

To further demonstrate the increase in impact resistance of such articles, two Groups of crucibles made from the same glass and treated according to the same ceramic formation scheme. They were subjected to a drop ball impact test in which a steel ball weighing 225 g dropped onto the center of the bottom surface of the object, taking the ball out each increasing height dropped until breakage occurred. In this experiment, the untreated showed Crucible an average impact strength of 0.042 kilograms and the treated Crucible had an impact strength of 0.334 kilogram meters.

Example 3

A glass with the following calculated composition (percent by weight): 62.5 SiO ₂ , 24.0 Al ₂ O ₃ , 4.9 Li ₂ O, 4.8 TiO ₂ , 0.5 F, 1.4 CaO was melted, drawn out into rods and converted into a glass-ceramic material by heat treatment according to the treatment scheme of Example 1. The resulting glass-ceramic rods had a primary crystalline phase of jβ-spodumene. These rods were divided into two groups for a thermochemical ion exchange treatment in a 85% NaNO ₃ -15% Na ₂ SO ₄ -Salzschmelzbad at 580 ° C. One group of samples was removed from the bath after half an hour of treatment and the other group after 3 hours of treatment. The calculated average breaking modulus values were 8580 kg / cm ² for the group with the half-hour treatment and 9080 kg / cm ² for the group with the 3-hour treatment.

Example 4

Glass ceramic rods of the / S-Spodument type were produced according to the method of Example 1 and divided into groups of six samples each for an ion exchange treatment in a salt bath consisting of a 52 to 48 weight percent mixture of KCl and K ₂ SO ₄ . The bath was kept at a temperature of 720 ^° C. and each group of samples was immersed for 7 hours; this time-temperature scheme was considered

Particularly effective for the solidification was recognized glass ceramic occurring maximum temperature in the. The order of magnitude is from 550 to 600 ^° C., however

After removal from the bath and cleaning, this temperature is only partially when it is put in and out the groups of samples in air in one turn is achieved. To determine the mechaelectric heated oven further heated, with the 5 niche strength an attempt was selected The time and temperature of the heat treatment, which consists in the fact that one weighs 2 kg drops between the individual groups of a reference metal vessel on the surface of the pane, reasons were varied. Following this, if the subject successfully passed this additional test Any heat treatment was to stand up to heat, it must be the impact of this vessel treated pieces subject to tumbling abrasion withstand 10 10 times from a height of 1.80 m, and its modulus of rupture is determined. At the beginning of this experiment, both survived

For purposes of comparison, further groups were prepared and immersed for 3 hours in a melt-lightness, as shown by their relatively identical bath, consisting of 85 % NaNO ₃ and 15 ° / ₀ 15 strengths were to be expected in the rod samples. Na ₂ SO ₄ and was kept at 475 ° C. After 1 week of trial operation, however, the samples were cleaned and each group was subjected to a heat treatment of 1.80 m one group was subjected to potassium ion exchange by potassium ion exchange disks after 3000 berries. The samples were then rubbed and kept for hours of floating. its strength is determined in the same way as that
of the potassium samples.

The following table gives the calculated example 5

Average modulus of rupture (in kg / cm ² · 10 ⁺³ ) 25

for each group of samples and the relevant The table below gives (in percent by weight)

Heat treatment again. Below the time zero is the calculated compositions of three glasses each time a group of specimens indicated the sern again that converted to glass-ceramics had been and could be set aside without treatment, which had a stable / S-eucryptite-

30 crystal phase. The average coefficient of thermal expansion of each glass (times 10 ~ ₇ and between 0 and 300 ⁰ C) is also given.

as a comparison standard Tem
temperature
⁰ C served. Time (St.
10 to the)
100 1000 ion 400
500
500
600 0 2.81
1.76
3.31
3.44 1.55
0.85
3.02
2.39 0.98 N / A 3.44
3.02
3.31
3.31 N / A - K K

SiO ₂ 48.5 45.6 39.8

Al ₂ O ₃ 38.0 39.9 35.7

Li ₂ O 8.5 9.5 7.5

₄₀ TiO ₂ 5.0 5.0 5.0

From this table it can be seen that the by BaO - - 12.0

Sodium ion exchange solidified the sample Strength from a 100 hour treatment

at 400 ⁰ C largely lost and over 1000 hours groups of glass-ceramic rod sample

completely lost at this temperature. The 45 produced from each glass and then subjected to an ion-cutting modulus of rupture for an abraded sample exchange treatment at 580 to 590 ° C, before the ion exchange is about 844 kg / cm ² . by immersing a group of rod specimens for a period of time appropriate to the potassium ion in a molten salt bath of non-exchangeable specimens - 85% NaNO ₈ and 15% Na ₂ SO ₄ lost in 10 hours at 600 ° C and kept a 50 which was kept at a constant temperature, substantial part of the strength even after 100 hours. This means that the thermal additive each ion-exchanged sample is subject to tumble abrasion resistance or the maximum permissible operating mode and determines its modulus of rupture, as described above for the temperature for ion-exchanged β-spodumene glass.

ceramics at least around 200 ⁰ C for a potassium 55 The following compilation shows the objects subjected to ion exchange higher maximum temperature, up to which each group lies than for a sodium ion exchange of samples in the ceramic objects in question. treatment has been heated, the expansion

About these results with regard to the strength coefficient of the resulting glass ceramic loss on a practical field of application to 60 terials, relating the time and temperature of the ion, Another attempt was made with quadra-exchange and the treatment given table disks from the average modulus of rupture achieved by glass-ceramic material carried out, which solidified an ion exchange and in the tumble-edge length of 25 cm and a thickness of approximately rubbed glass-ceramic samples. All temperatures 0.034 cm. Such disks are used as the basis for 65 are in degrees Celsius and all times are in minutes a heating element determines which one is indicated on the one. In each case it was the predominant one Side of the disc is mounted on. It becomes crystal phase ß-eucryptite, as taken by X-ray, that during operation it could be shown in the diffraction analysis.

Ceramics the end Ion off fracture Glass educational elongation exchange
7ρλ \ ΊϊτΐίΊ module temperature coefficient £ -XiiX UUU
temperature (times 10+ ³ ) 1 720 3.9 20-580 2.72 1 830 1.6 20-580 1.91 1 1060 1.5 10-580 2.43 1 1060 2.0 10-580 '2.31 (60 minutes stop) 1 1200 2.3 20-580 2.25 2 700 5.6 10-590 2.07 2 835 6.6 20-590 2.34 2 1100 6.7 20-590 2.71 2 1195 6.3 10-590 1.92

By comparison, untreated glass-ceramic rods made from each glass, which had been rubbed down in the same way, showed average modulus of rupture of 560 to 630 kg / cm ² . . The glass No. 3 was as follows converted into a glass ceramic: heating at 300 ° C / hour to 965 ⁰ C; there held an hour; Heating at 10 ° C / hour to 705 ° C; Heating at 300 ° C / hour to 112 o ⁰ C; held there for 4 minutes; Heating at 10 ° C / hour at 117O ⁰ C; held there for 30 minutes; Cooling down.

/ S-eucryptite and celsian (BaO · AIgO ₃ · 2 SiO ₂ ) were observed in larger crystalline phases; the glass-ceramic material had an average coefficient of expansion of 14.4 · io- ₇ / ° c.

The rod samples were 10 minutes in the 85% NaNO ₃ ~ - immersed to 15% Na ₂ SO ₄ -Salzbad at 580 ⁰ C, cleaned, rubbed and tested as usual. The average modulus of rupture for these samples was 1760 kg / cm ² compared to an average modulus of rupture of 950 kg / cm ² for abraded, but untreated, glass-ceramic rod samples.

Example 6

0.6 cm thick cylindrical glass-ceramic test pieces were made from a glass of the following calculated composition (weight percent on oxide basis): 70.8% SiO ₂ , 18.6% Al ₂ O ₃ , 4.4% MgO, 1.9% Li ₂ O, 3.8% ZrO ₂ and 0.5% As ₂ O ₃ . The glass-ceramic material was characterized by a / 3 quartz type crystal phase. The glass was converted to the glass-ceramic state using a heat treatment scheme in which the material was held at 780 ° C, 850 ° C and 900 ° C for 4 hours each. Between these temperatures, the furnace was heated at maximum speed and, after the heat treatment had been completed, cooled by opening it in the air.

The thus obtained glass-ceramic rods were cut in lengths of 10 cm and immersed for 6 hours in a molten salt bath, which consisted of 48% K ₂ SO ₄ and 52% KCl, and was maintained at a temperature of 78o C ^0. After cooling and cleaning, the rod samples were rubbed in a tumbler and their individual and average modulus of rupture was determined. This resulted in a strength ^{value of 3650 kg / cm 2} for this particular material and this ion exchange treatment. By comparison, an untreated rod that was rubbed in the same way has an average modulus of rupture of about 844 kg / cm ² .

Example 7

A series of rod specimens which, as described above, are converted into the ceramic state and had been solidified, were exposed to different lengths of time at different temperatures in the air

ίο warmed up. After this treatment, they were rubbed in a tumbler and their modulus of rupture was determined in the usual way. The table below shows the times (in hours) and temperatures (in ° C.) of the treatment and the average modulus of rupture after abrasion (in 10 ³ kg / cm ² ), which had been determined for each group after the specified treatment.

20th 500 °
600 °
700 ° temperature 0 Time in stunc
10 en 100 C. 3.65
3.65
3.65 3.61
3.59
2.69 C. C. 3.23 3.49 3.48

These data indicate the ability to maintain strength at high temperatures or the resistance to thermal degradation that characterize the ion exchange solidified / S-quartz glass-ceramics. Because of this property, they are suitable for long-term use at temperatures of the order of 600 to 700 ⁰ C.

Example 8

Another group of glass-ceramic rod samples, which had been produced as described in Example 6, was immersed in the same salt bath which was kept at 750 ^° C. for 16 hours.

The average modulus of rupture calculated for this series of samples after a comparable abrasion treatment was 3530 kg / cm ² .

This means that comparable strengths can be obtained at slightly lower temperatures and longer Times can reach.

Example 9

A glass with the following calculated composition in percent by weight: 71.0 SiO ₂ , 18.7 Al ₂ O ₃ , 3.6 MgO, 2.6 Li ₂ O, 3.5 ZrO ₂ and 0.6 As ₂ O ₃ was converted to the glass-ceramic state according to the heat treatment method of the preceding examples. Two sets of rod samples were then prepared for the ion exchange treatment.

One set was immersed in the 48% -K ₂ SO ₄ -52% -KCl salt bath at a temperature of 720 ° C for 16 hours. The second row was immersed in this bath at 780 ^° C. for 5 hours. After cooling and cleaning, the rod samples were rubbed in a tumbler and then loaded in order to determine their flexural strength according to the method described in Example 1. The calculated average modulus of rupture for the ^{samples treated at 720 °} C. was 3130 kg / cm ² , while the comparison value for the ^{samples treated at 780 °} C. was 2580 kg / cm ² , from which it can be seen that at 780 ^° C. a slightly longer treatment time for optimal consolidation is required.

909 504/1523

Examples 10 to 13

Several groups of / J-quartz type glass-ceramic rod samples were made from the material and after following the procedure of Example 6.

Each group was first immersed in a salt bath, which consisted primarily of lithium sulfate and was diluted with potassium or sodium sulfate or acid sulfate. The treatment bath was kept at 775 ^° C. and the treatment was carried out for either 4 or 8 hours. The groups of samples were then removed and cleaned and then placed in a second bath consisting of 48% potassium or sodium sulfate and 250% potassium or sodium chloride. These salt baths were also held at 775 ° C and the treatment time was either 4 or 8 hours. After removal from the salt bath and cleaning, each rod sample was tumbled and the modulus of rupture determined.

The table below lists a number of such ion exchange treatments, the original lithium salt bath composition (first bath), the type of salt (sodium or potassium) used in the second salt bath, the time (in hours) of the respective ion exchange treatment and the average modulus of rupture (in kg / cm ² times 1O ⁺³ ) for each group with the appropriate treatment indicated. Second bath was immersed, which was kept at 800 ° C and consisted of 80% K ₂ SO ₄ and 20% Li ₂ SO ₄ .

Following this second ion exchange treatment, in which the lithium ions introduced by the first bath were replaced by potassium ions, the glass-ceramic rods were cleaned again and rubbed down in the usual manner. Each abraded sample was then loaded until it was destroyed ίο and the individual and average modulus of rupture was calculated. The average modulus of rupture after abrasion of the rods treated in this way was 4190 kg / cm ² .

Example 15

The table below is a number of exemplary oxide-based glass compositions given in percent by weight, which are able to form a glass ceramic of the nepheline type:

First bath Second bathroom Time fracture
module 65% Li ₂ SO ₄
35% KHSO ₄ potassium 4 - 4
8 - 8 1.05
3.09 75% Li ₂ SO ₄
25% KHSO ₄ sodium 4 - 4
8 - 8 1.12
2.25 65% Li ₂ SO ₄
35% KHSO ₄ sodium 4 - 4
8 - 8 0.63
2.32 80% Li ₂ SO ₄
20% KHSO ₄ potassium 4 - 4
8 - 8 1.12
2.04

1 2 3 49.5 47.5 48 26th 28 34 17th 17th 18th 5 5 8th 0.5 0.5 0.5 2 2 -

By comparison, untreated and abraded glass-ceramic samples typically have a modulus of rupture of about 562 kg / cm ² . After 4 hours of treatment at 775 ° C in a lithium salt bath, as shown in the table above, the modulus of rupture of an abraded sample is essentially unchanged, while after 8 hours of treatment at this temperature the modulus of rupture after abrasion is about 914 kg / cm ² amounts to.

Example 14

A second glass-ceramic material of the / 3 quartz type became rod samples in essentially in the same way as described above. This second glass-ceramic material had the the following oxide composition (in percent by weight):

47.5 SiO ₂ , 37.5 Al ₂ O ₃ , 15 MgO and 12 ZrO ₂ .

A series of 0.6 cm thick rods made of this glass-ceramic material were immersed for 16 hours in a molten salt bath, which was kept at 790 ° C. and consisted of 75% Li ₂ SO ₄ and 25% K ₂ SO ₄ . After that, this group of samples was taken and cleaned and then 8 hours in one

SiO ₂ 49.5 47.5 48 40

Al ₂ O ₃ 26 28 34 32

BaO - - - 16

Na ₂ O 17 17 18 12

TiO ₂

As ₂ O ₃

MgO

0.6 cm thick glass rods were heat treated in the glass ceramic State, with a nepheline crystal phase in glasses 1 to 3 and a mixture of nepheline and Celsian crystal phases were generated in glass 4. The heat treatment applied to each glass was like this:

1 + 2 with 200 ° C / hour to 68O ⁰ C; at 60 ° C / hour to 1040 ° C;

2 hours hold at 1040 ° C; cool down at 200 ° C / hour.

3 at 300 ° C / hour to 850 ° C; 4 hours hold at 85O ⁰ C;

at 300 ° C / hour to 110O ⁰ C; 4 hours hold at HOO ⁰ C; cool in the oven.

4 at 300 ° C / hour to 850 ° C; 4 hours hold at 850 ° C;

at 300 ° C / hour to 116O ⁰ C; 4 hours hold at 116O ⁰ C; cool in the oven.

The glass-ceramic rods so produced were then grouped for the ion exchange solidification treatment. This treatment consisted of immersing each group in a molten potassium salt bath at a specified temperature and for a specified duration in order to effect an exchange of potassium ions from the salt bath for sodium ions from the nepheline crystals in a surface layer of the rods. Both the time and the temperature of the treatment were varied within the individual groups in order to determine the influence of such variations. _{A potassium nitrate bath (KNO 3} ) was used for temperatures of 600 ° C and below, while for

higher temperatures a bath composed of 52% potassium chloride (KCl) and 48% potassium sulfate (K ₂ SO ₄ ) was taken.

After the salt treatment, each rod was cleaned and tumbled before the modulus of rupture determined in the usual way.

The table below summarizes the various ion exchange treatments, composition number, salt bath temperature (temperature), treatment time, and calculated average modulus of rupture (times 10 ^{+ 3} ) for each group of samples.

to Tem Time Rupture modulus times 10+ ³ kg / cm ² with abrasion together temperature 0.77 settlement ⁰ C hours without abrasion 0.77 1 1.69 0.63 T-H 525 4th 3.59 3.09 1 525 16 3.66 0.84 T-H 580 72 - 0.56 2 - - 1.48 0.70 2 525 4th 4.22 0.84 2 525 16 4.85 6.12 3 590 8th - 5.20 3 590 96 - 8.65 3 730 8th - 0.70 3 775 8th - 4.01 4th 500 4th - 4th 550 64 -

Example 16

A series of glasses was put together, which had the "potassium" crystal forms mentioned earlier included. In these glasses, sodium oxide and silicon oxide were passed through in a selected base glass Replacing increasing amounts of potassium oxide. The glass compositions are as follows Table compiled in parts by weight based on oxide of the mixture. The table also shows the "x" value for the potassium ion in the nepheline crystal phase, which develops when the glass is in the glass-ceramic State is transferred.

G H I. J L. N O U 47.9 47.7 47.5 47.3 46.7 46.1 45.6 45.1 34.0 34.0 34.0 34.0 34.0 34.0 34.0 34.0 18.1 17.9 17.6 17.0 15.9 14.7 13.6 12.7 0.0 0.4 0.9 1.7 3.4 5.2 6.8 8.2 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.0 0.1 0.25 0.5 1.0 1.5 2.0 2.4

SiO ₂ ..
Al ₂ O ₃ .
Na ₂ O.
K ₂ O ..
TiO ₂ .
As ₂ O ₅
χ (mole)

44.6

34.0

11.8

Rods 0.6 cm thick from each glass were converted to the glass-ceramic state by the following heat treatment:

Ceramic formation cycle

Heating to 850 ⁰ C and 300 ° C / hour;

4 hours hold at 850 ° C;

warm to HOO ⁰ C at 300 ° C / hour;

4 hours hold at 1100 ^° C .;

cool in the oven.

Two groups of 10 cm long rods of each composition were then selected and one group of each was subjected to each of the following ion exchange treatments:

1. 8 hours immersion in a bath of molten potassium nitrate (KNO ₃ ) at a temperature of 590 ^° C .;

2. 8 hours of immersion in a molten bath of 52% KCI and 48% K ₂ SO ₄ at 73O ⁰ C.

Following this treatment, each rod was cleaned and tumbled before the modulus of rupture was determined. The calculated average modulus of rupture (times 1O ⁺³ ) for each group is given in the table below:

sample bath Average
Modulus of fracture times 1O ⁺³ G 1
2 0.87
5.17 G 1
2 0.83
6.87 H T-H CS τ- 1.15
4.62
4.10 H 2
1
2
1 11.40
6.13
14.25
6.68 I. 2 13.77 I. 1
2
1
2 7.24
13.08
8.70
11.80 J 1
2 8.80
13.91 J L. L. N N O O U U W. W.

Example 17

A glass was produced which had the following calculated composition in percent by weight Oxide base had:

45 SiO ₂ , 40 Al ₂ O ₃ and 15 Na ₂ O.

Sheets were cast and cut into rectangular bars 4.5 x 6 x 120 mm which were cut into a glass-ceramic state characterized by a Carnegieite crystal phase the following heat treatment have been converted:

Heating at 300 ° C / hour to 850 ⁰ C;

4 hours hold at 85O ⁰ C; * 5

heat at 300 ° C / hour to HOO ⁰ C;

4 hours hold at HOO ⁰ C;

cool down at the airspeed of the
Furnace. _ao

A number of the glass-ceramic test rods produced in this way were immersed in a molten salt bath consisting of 52 percent by weight KCl and 48 percent by weight K ₂ SO ₄ . After being immersed in this bath at 575 ^° C. for 8 hours, the test rods were removed, cleaned and rubbed in a tumbler before the modulus of rupture was determined. The ion-exchanged test samples had an average modulus of rupture after tumbling abrasion of 2300 kg / cm ² . In comparison with this, untreated glass-ceramic test rods, which had been abraded in a similar manner, had a modulus of rupture after abrasion of 1200 kg / cm ² .

Claims (5)

Patent claims: 1. A method for solidifying a glass-ceramic object, which is used as an exchange 35 bares alkali metal ion containing stem crystal phase / J-spodumene, thermally stable ß-eucryptite, nepheline, carnegieite or /? - contains quartz, characterized in that the surface of the object is kept in contact with a material which contains an ion whose ion diameter is greater than that of the alkali metal ion of the parent crystal phase and which is exchangeable with the latter in order to exchange larger ions and alkali metal ions within a surface layer of the object with one another and in this way develop compressive stresses in this surface layer. 2. The method according to claim 1, wherein the parent crystal phase /? - is spodumene or thermally stable ß-eucryptite, characterized in that the surface of the object is kept in contact ^{with a bath of molten sodium salt at a temperature above 450 ° C.} 3. The method according to claim 1, wherein the parent crystal phase containing lithium ions / 5-spodumene, thermally stable / J-eucryptite or / S-quartz, characterized in that the surface of the object with a bath of molten potassium salt at a temperature of Keeps 550 to 800 ⁰ C in contact. 4. The method according to claim 3, characterized in that the potassium salt bath consists of 50 to 60 ° / ₀ KCl and 40 to 50% K ₂ SO ₄ . 5. The method of claim 1, wherein the parent crystal phase is potassium and sodium ions containing nepheline is characterized in that the ratio of potassium ions to sodium ions in the nepheline crystal phase is at least 1:31, preferably more than 1: 4, and the surface of the object in contact with molten potassium salt. .