DE4133370A1 - Amorphous glass colloid - contains homogeneous and consistent oxide complex within the glass matrix - Google Patents

Abstract

The amorphous glass colloid with at least one polyoxometallate electro- or photochrome characteristic through its layered oxide complex in the glass matrix, has the oxide complex distributed in a homogenous concn. with an even size, structure and rating. The oxide complex has a freely selectable concn., size and structure and rating. The oxide complex is derived from iso- and/or heteropolyoxometallates with free choice of type and/or mixt. Additional oxidn. redn. components can be added for durable tinting and rapid colour neutralisation. The glass colloid is a silicon-borate glass with an inlaid wolframate cluster as the oxide complex, of a given species and esp. dekawolframate. The material is a colloidal coating mass, a thin and stable film, or a stable glass. USE/ADVANTAGE - The material is for use in solid state applications, such as smart windows, light filters, displays, spectrography, laser technology and the like. The glass colloid is monolithic, transparent, and reversibly electro- or photochrome. It is insensitive to moisture, and thermally stable at very high temps.

Description

The invention relates to amorphous glass colloid, the through oxide complexes embedded in its glass matrix at least one polyoxometalate electro- or photochromic Has properties and a method for its Manufacturing.

Such amorphous glass colloids are for example from Braunstein has been developed (R.Braunstein, Solid State Commun. 28 (1978), 839 and J.N. Crys. Solid 108 (1989), 109). He suggested tungsten oxide (tungsten trioxide) in one Solve glass matrix to electro- and photochromic glasses receive. These are glasses that are under the Influence of energy supply by applying a voltage or Irradiate with light due to internal changes in their Molecular states change their absorption behavior.

Because the glasses developed after Braunstein are a random one and unknown internal distribution of the introduced Have tungsten oxides, and the tungsten oxides as a mixture different clusters, that is, in agglomerated ones Molecular complexes with completely unknown size and structure can occur via the electro- or photochromic Behavior of such glasses is only relatively imprecise statements be made. Neither strength nor speed Reactions can be determined exactly. Also one can different occurrences of the reactions within one Glasses are not affected, and the ferroelectric  Behavior is unsatisfactory. So there is none Possibility of behavior developed after Braunstein Modify or modify glasses with tungsten oxide influence. The making of predetermined structures is not possible. The glasses are difficult to identify reproducible.

These properties are based essentially on the type of Manufacture of such glasses. You will after the High temperature process manufactured in which the individual Components at very high temperatures (about 1200 degrees Celsius) mixed together by melting and pre destruction of individual components cooled down again will. A control of the response time between the individual components are therefore not possible. The must also Tungsten oxide content is almost 50% to even one Get clustering. This creates transparency of the glass very severely restricted. Cluster formation is also affected by the response time. This must be very be short, but this makes the homogeneity of the glass negative being affected. Furthermore, during the fast Melting process the porous material is not sufficient be compacted so that it is sensitive to Moisture remains. The mixture of the individual components in the molten state also leads to the fact that finished material is thermally unstable. Movies can with not be manufactured using this method. By the required high energy input and share of Tungsten oxide is a relatively expensive manufacturing process complex.

Therefore arises precisely with regard to the constantly growing demands on electro- or photochromic Materials for a wide range of applications the basic demand for a material whose fully known electro- or photochromic properties and can therefore be used accordingly. Always the same lasting quality and reproducibility at the  Production of the material must be guaranteed. Also one is targeted controllability of the material properties to strive for. In addition, there are always economic aspects to be observed. The material should be reasonable Price can be manufactured.

The glass colloid can meet such high requirements Fulfill the invention in that the oxide complexes in one homogeneous concentration and in size, Structure and value are fully determined. This applies in particular when more advantageous Embodiments of the glass colloid according to the invention Concentration and / or the size and structure and / or the Values of the oxide complexes are freely selectable.

According to the requirements for the glass to be manufactured Material can thus be electro- and photochromic Properties that depend on the structure, composition and the electrical charge of the embedded oxide complexes are dependent, freely chosen and beyond can be set. It is the properties primarily about the absorption behavior of the material, which also the color strength and structure and thus determines the contrast behavior. Completely even Color distributions and very sharp contrasts are achieved. Furthermore, other parameters such as transparency, Reversibility of the coloring and long-term behavior, selected and controlled.

One obtains with the glass colloid according to the invention amorphous material with a predeterminable and even selectable local substructure through which the material has become freely adaptable and modifiable. A is targeted molecular design within a glass matrix possible. It is a completely new class of mixed-value glasses with electro- and photochromic Properties. Especially for basic research the field of molecular structures and for  This is a further development of the electron transfer theory essential.

Essential requirement for modifiable glass colloids with designed substructures, the process is theirs Manufacturing. Therefore, a method according to the invention for the production of an amorphous glass colloid, which by in its glass matrix embedded oxide complexes at least one Polyoxometalates electro- or photochromic properties has applied, which is characterized in that the oxide complexes in the homogeneous concentration and with the exactly determined size and structure according to itself known sol-gel process at room temperature in the Glass matrix can be stored.

In the example of Chemseddine et al. (Solid State Ionic 9-10 (1983), 357) known sol-gel methods the required oxide complexes of a polyoxometalate in a suitable solution at room temperature to the poly merization stimulated. So far, using this method but only made thin films to coat Electrodes were used. But such films show different reactions (contrast, Color changes and reaction speed) and have a relatively poor filter behavior. This is due to the unknown, uneven distribution of tungsten Clusters of different sizes and structures within the Footage. Such films are also moist sensitive to sensitivity and due to their low manufacturing quantities costly.

The manufacture of glasses using the sol-gel process by Ulrich (J. N. Cryst. Solids 121 (1990), 465). A reference to the use of such glasses with electronic or photochromic requirements, however, it does not take.

Those produced according to the invention with the sol-gel process Amorphous glass colloids are monolithic, transparent and  reversible electro- or photochromic. You are insensitive against moisture and also thermally absolutely stable at very high temperatures. Also their creep behavior is stable. They are in their optical properties adjustable and can be due to the relatively slow Polymerization process also good in every intermediate state stabilize. They have stable ferroelectric properties create and are therefore also for switching and Suitable measuring devices. With the manufacturing process large amounts of glass colloid can be quickly any dimensions using only very small Produce proportions of polyoxometalates. From innkeeper From a economic point of view, this is a major advantage of glass colloids according to the invention.

The glass colloids according to the invention are particularly suitable for example for the production of so-called "smart windows ". These are" thinking "windows, which their absorption behavior towards heat radiation can adapt to the respective conditions. The controller can by the sunlight itself or by applied Tensions occur. Use with glasses for Glare absorption is well known. The entire filter technology calls many applications possibilities, especially with spectroscopy and with of laser technology. A large area of application are also Display devices of any kind. Especially very large Ads that quickly change color homogeneously and with high Have to perform contrast - for example stadium or Billboards - can with the glass according to the invention colloid advantageously be equipped. But also smaller ones Display devices such as those found in fittings board of a car or a wristwatch will be realized. The invention is for all industries branches with imaging media of great importance. Last is still a particularly innovative application called: the glass colloid according to the invention is also for  Manufacture of optical memories for optical computers suitable.

The usability of the glass colloid according to the invention is further increased if according to another advantageous Design the oxide complexes of iso- and / or hetero polyoxometalates descended in their type and / or Mixture are freely selectable. The type of chosen Polyoxometalates determine the absorption and thus also the color behavior of the glass colloid. For example, you choose Tungsten for the oxidation gives a blue color. If you choose other transition metals, such as. B. molybdenum, Vanadium, niobium or tantalum, you get another one Absorption and thus color behavior. For applications in colored display devices, this is particularly cheap. The same applies to the use of heteropolyoxometalates. The iso- and heteropolyoxometalates are therefore the Selection group for the oxide complexes and also serve the Inclusion of further doping elements. Depending on the requirements to the electro- and photochromic behavior of the invention According to glass colloids, they can be used individually or as a mixture component used in discrete or mixed form will.

The same explanations apply if there is a corresponding further embodiment of the invention according to the Glass colloid doped with an additional redox component becomes. This will permanently color the glass achieved, for example, its contrast to that respective background significantly increased. Because in most Cases of glass colloids due to an appropriate oxide doping in different shades of blue can respond, for example, by using Cobalt or cerium as the dye element is the basic setting be improved. On the other hand, is after another Further development of the glass colloid according to the invention another additional redox component for quick  Color neutralization doped, you get particularly reactive fast electro or photochromic glasses.

All statements made so far are general and serve the purpose of that for each special application to be able to determine the best possible glass colloid. Experiments have shown that, as in another invention described in accordance with the configuration, is advantageous if the glass colloid is a silicon borate glass in which as Oxide complex tungstate clusters of a certain species, in particular Dekawungframat, is stored. With spend research methods, such as absorption spectroscopy, X-ray analysis, electron spin resonance method and Differential thermal analysis, it was confirmed that a Such glass colloid optimal electro- or photochromic Has properties. This also applies to others, already mentioned advantages, such as temperature and time stability. The outstanding suitability of the invention is essentially based appropriate glass colloids on the now obtained Findings that it describes the absorbency The amount of energy that can be absorbed depends on the Molecular structure between the metal and the oxygen components of the polyoxometalate. These structures will be of oxygen bridges with different angles of inclination formed between the metals. To overcome linear The valence electron requires less energy than for bridges Overcoming steep bridges. The amount of energy absorbed or the color behavior are different. That's why the absorption behavior is adjustable through the choice the species and thus the bridge structure within one Polyoxometalate clusters.

Other possible species of polyoxometalates for formation the oxide cluster is tungsten in hexa, meta or para form or are decavanadate or hexamolybdenum. The value of the The oxometalates used can either be electrolytic under the influence of current, photochemically for a long time Irradiation times or by installing additional ones  Electron donors can be set. Mostly they are Poloyoxometalates mono- or divalent.

For certain applications, it is not only important that glass-optical behavior, but also choose the physical state of the amorphous glass colloid yourself to be able to. Therefore it is convenient if according to others Refinements of the glass colloid according to the invention, this as a sol-like mass for coatings, as a thinner, stable film or a solid glass. Therefore the type of manufacture is essentially responsible process according to the sol-gel process. With this it can Glass colloid made in different states will.

When using the sol-gel process, it is according to one Design of the manufacturing process for the invented glass colloid according to the invention is particularly advantageous, the following Perform process steps:

• - Add and mix several glass forming components for the production of the glass matrix,
• - Add and mix slightly acidic water for heterolysis and thus to trigger the polycondensation or Polymerization,
• - Add and mix acetic acid as a bubble buffer homogeneous glass formation,
• - adding and mixing a particular species of an iso- and / or heteropolyoxometalates in acidic form,
• - Long-lasting mixing of all components and, depending on the application, alternatively the process steps
  • a) coating surfaces with the resulting sol,
  • b) drawing films from the resulting sol while mixing, or
  • c) transferring the resulting sol into containers of the required size,
• - Storage of the containers over several days at elevated Temperature to form a dried, solidified gels,
• - Further temperature treatment of the dry gel high temperature to remove organic Materials and
• - Remove the finished glass from the containers.

The glass colloid produced in this way is in its optical and other properties precisely characterized and set. This is especially true if according to one further inventive design of the manufacture procedure

• - The glass-forming components boric acid, tetramethoxysilane and are tetraethoxysilane,
• - the species of polyoxometalate is decungstate which dissolved by adding an organic solvent and is stabilized, and
• - The temperatures for drying or removal all organic material are 60 or 600 degrees Celsius.

In the following, more detailed explanations are given, the also serve to explain the figure. The figure shows a flow chart for the preparation of the invention Glass colloids according to the sol-gel process in a special preferred embodiment. All used there Components can be processed as they are on the Market. Other intermediate treatments are not mandatory.

In a process step I, three glass-forming components 1 , 2 and 3 are brought together at room temperature T. Component 1 in the selected example is 0.51 g of a boron oxide, in the present case boric acid, which is dissolved in 5 ml of methanol. The use of boron has the advantage that it has strong sintering properties in the glass formation, so that there is a glass densification and thus the removal of large glass pores. However, other alkoxides can also be used, such as those of silicon, phosphorus, germanium or aluminum. Component 2 is 5 ml of dissolved tetramethoxysilane (TMOS) and component 3 is 5 ml of dissolved tetraethoxysilane (TEOS). The polymerization process can be controlled with these glass-forming elements based on silicon. By mixing both components 2 and 3 , which have different reaction times, the resulting glass structure can be influenced in its optical and thermal properties.

In a process step II, components 1 , 2 and 3 are mixed intensively for 5 minutes with constant stirring.

Then 5 ml of a component 4 are added in a process step III. Component 4 is slightly acidic water with a pH of 2, which is formed by adding hydrochloric acid. The addition of water triggers the hydrolysis and thus the polymerization and polycondensation process of components 1 , 2 and 3 (indicated by an arrow 5 in the flow diagram).

In a process step IV, the crosslinking Mix well by stirring for 5 minutes to make a To achieve homogenization of the polymerization.

To be able to run around the glass forming process homogeneously, ie to avoid formation of bubbles, are in a next method step V as a component 6 2 ml of acetic acid, which acts as a buffer was added.

In a process step VI everything is under again Stir well mixed for 2 minutes.

As the next, very essential process step VII, a component 7 is added. In the example selected, this is 10 ml of a polyoxometalate in the form of a tungstate species. Such oxides are produced, for example, by ion exchange between sodium tungstate and water and then stabilized by the addition of an organic solvent, for example acetone, DMSO or DMF. The manufacture is well known. The addition takes place in acid form. An addition in salty form is also possible.

In a next process step VIII, the increasingly cross-linking agglomerate is mixed well for 30 minutes. During this mixing process, the homogeneous concentration distribution of the precisely known tungstate species as oxide complexes or clusters is achieved. A cluster mix does not occur. The addition of the solvent as an electrolyte causes the embedded tungsten clusters to be mono- and divalent. After process step VIII, a glass colloid in the form of a sol 8 was formed. This can be used to coat surfaces.

However, stable films 9 can also be drawn therefrom in a method step IX.

As a third alternative, it is possible to transfer the sol 8 into beakers in a further process step X, the shape and size of which depend on the intended use, and there, with the exclusion of air, in an oven at about 60 degrees Celsius for 6 days to form a solidified gel 10 ( Xero-Gel) to dry.

In a further process step XI, the gel 10 is then subjected to a further heat treatment at approximately 560 to 600 degrees Celsius. This serves to burn away all organic residues. It turns out that the gel 10 is stable even at such high temperatures.

After the heat treatment, a solid glass 11 is then formed which, because of the homogeneous distribution of the clusters of the tungsten species 7 used, has the desired electro- and photochromic properties.

Claims (14)

1. Amorphous glass colloid which has electro- or photochromic properties due to the oxide complexes of at least one polyoxometalate embedded in its glass matrix, characterized in that the oxide complexes are distributed in a homogeneous concentration and their size, structure and value are completely determined. 2. glass colloid according to claim 1, characterized in that the concentration of the oxide complexes can be freely selected. 3. glass colloid according to claim 1 or 2, characterized in that the size and structure of the oxide complexes can be freely selected are. 4. glass colloid according to claim 1, 2 or 3, characterized in that the valence of the oxide complexes can be freely selected. 5. glass colloid according to one of the preceding claims, characterized in that the oxide complexes of iso- and / or heteropolyoxometalates descend, freely selectable in their type and / or mixture are.   6. Glass colloid according to one or more of the preceding Expectations, characterized in that it with an additional redox component for permanent Coloring is endowed. 7. Glass colloid according to one or more of the preceding Claims 1 to 5, characterized in that it with another additional redox component rapid color neutralization is doped. 8. Glass colloid according to one or more of the preceding Expectations, characterized in that the glass colloid is a silicon borate glass in which as Oxide complex tungstate clusters of a certain species, in particular Dekawungframat, are stored. 9. Glass colloid according to one or more of the preceding Expectations, characterized in that it is designed as a sol-like mass for coatings. 10. Glass colloid according to one or more of the preceding Claims 1 to 8, characterized in that it is formed as a thin, stable film. 11. Glass colloid according to one or more of the preceding Claims 1 to 8, characterized in that it is designed as a solid glass.   12. Process for producing an amorphous glass colloid, the oxide complexes embedded in its glass matrix at least one polyoxometalate electro- or photochromic Has properties characterized in that the oxide complexes in the homogeneous concentration and with the precisely determined size, structure and value Application of the known sol-gel process in Room temperature can be stored in the glass matrix. 13. Sol-gel process for producing a glass colloid according to claim 12, characterized by the following process steps:

• Adding and mixing (I, II) a plurality of glass-forming components ( 1 , 2 , 3 ) to produce the glass matrix,
• Adding and mixing (III, IV) slightly acidic water ( 4 ) for hydrolysis and thus for triggering the polycondensation or polymerization ( 5 ),
• - Add and mix (V, VI) acetic acid ( 6 ) as bubble buffer for homogeneous glass formation,
• Adding and mixing (VII) a specific species ( 7 ) of an iso- and / or heteropolyoxometalate in acidic form,
• - Long-lasting mixing (VIII) of all components ( 1 , 2 , 3 , 4 , 6 , 7 ) and
• - Depending on the application, the process steps alternatively
  • a) coating surfaces with the resulting sol ( 8 ),
  • b) pulling (IX) films ( 9 ) from the resulting sol ( 8 ) during mixing (VIII), or
  • c) transferring the resulting sol ( 8 ) into containers of the required size,
• - depositing (X) the container over several days at elevated temperature to form a dried, solidified gel ( 10 ),
• - Further temperature treatment (XI) of the dry gel ( 10 ) at high temperature to remove organic materials and
• - Removing the finished solid glass ( 11 ) from the containers.

14. Sol-gel method according to claim 13, characterized in that

• the glass-forming components ( 1 , 2 , 3 ) are boric acid, tetra methoxisilane and tetraethoxisilane,
• - The species ( 7 ) of the polyoxometalate is decatungstate, which is dissolved and stabilized by adding an organic solvent, and
• - The temperatures for drying (X) or further temperature treatment (XI) are approximately 60 or 600 degrees Celsius.