DE2510027A1 - METHOD OF MARKING SILICON NITRIDE - Google Patents

Description

Method for marking silicon nitride

The present invention relates to a method for marking silicon nitride.

Markings are made on silicon nitride articles, for example to identify the object itself or as a display element, applied if such an object as a kind of measuring instrument can be introduced into a process sequence together with other objects to be treated, for example in an oven or chemical process. It is therefore important to have markings on the silicon nitride, for example in the form of letters, numbers or symbols or colors, to be applied that are easy to read and use are resistant.

-2-

509837/0704

BERLIN: TELEPHONE (OSO) 8312Ο88 CABLE: PROPINDUS TELEX 01 84Ο67

MUNICH: TELEPHONE (OBB) 936685 CABLE: PROPINDUS TELEX OB 34244

These markings can be made by making indentations in the fresh, shaped body before firing but they can also be introduced into the body while it is being formed. These procedures are also already in place been adopted in the manufacture of labels made of silicon nitride, which are used as display elements for heat or chemical Treatments are used. A typical form of application is the labeling of steel bars that are subject to heat treatment or metal parts placed in an acid pickling bath. Due to the properties of silicon nitride these labels have a good resistance to the aforementioned extremely unfavorable environmental conditions, so this is a very good solution for Marking of components to be treated represents.

Where specific information should be readable through the mentioned impressions in the silicon nitride cannot be obtained, the flat surface can be sanded after firing, which gives a white inscription on a dark background, or the inscription itself can be burnt in with a diamond Silicon nitride, which results in a dark inscription on a white background. The latter is but extremely expensive.

Although the methods described compared to previous labeling methods represent a significant step forward, as they are comparatively high costs for each individual label connected and therefore not suitable for mass use.

The present invention is therefore based on the object of specifying a satisfactory marking method that allows the Allows user to mark the label immediately prior to its use.

509837 / Ö7CK

This object is achieved according to the invention in that a Mixture, consisting of a metal oxide and / or a raw material that provides a metal oxide when heated, a carrier liquid and a binder is applied to the silicon nitride and the silicon nitride is then applied in the furnace is burned.

The present invention provides chemical "paints" that are especially suitable for the white "like burnt" surface of the silicon nitride. However, you can also click on edited, For example, ground and fired surfaces can be applied. These "colors" consist of one or several metal oxides, depending on which color is required, a carrier liquid and a small amount of binder. This mixture is applied to the surface of the silicon nitride and then fired at a temperature that is at least is as high as the subsequent use temperature of the treatment, to which the silicon nitride item is subjected target. This temperature is between 600 C and 1600 C, preferably around 1000 ° C. The baking can also take place at the same time can be made during the later firing process, the temperature of which, for example, with the help of the silicon nitride object should be controlled 3.

Metal oxides can also be mixed in the mixture with a raw material which, when heated, yields a metal oxide. as Carrier liquid comes water or an organic liquid into consideration. The binder is expediently refractory and consists, for example, of a silicate, oxide, nitride, a clay or a glass. However, a temporary organic binder can also be used, for example an alginate ' or polyvinyl alcohol.

-4-

509837/0704

Some exemplary embodiments are to be described below.

example 1

As marking agents, iron oxide and cobalt oxide _were mixed in equal parts by weight with 0.5% by weight of silicon nitride powder as a refractory binder. This mixture was brought to a suitable consistency with water as the carrier liquid. The binder was applied to a "like fired" silicon nitride surface and then on for two hours
black.

Fired at 1000 ° C for a long time. The burned marker was

The article with the baked marking agent was then placed in boiling water for two hours, dried and then fired again at 1000 ° C to test the durability of the marking agent. It turned out to be this Treatment had no effect on the marking agent.

Example 2

A similar marking agent as in Example 1 was used and tested, but in which only cobalt oxide was present as the metal oxide. The burned mark was purple in color and was not affected by the subsequent tests.

Example 3

A marking agent was prepared in the manner of Example 1, with iron chloride and chromic acid in equal parts by weight or chromic acid was used alone. Chromic acid is soluble in water and provides chromium oxide when heated. 0.5% china clay was added as a refractory binder. The burned

509837/0704 ~ ⁵ ~

Marking agent was buff or brown in the first case and green in the second case and was replaced by the subsequent ones Attempts not affected.

Example 4

A marking agent was prepared as in Example 1, with iron oxide and porcelain clay in a ratio of 1: 3 with and without adding 0.5% by weight of a dispersing or stabilizing agent such as Alomium polyelectrolyte or 10% sodium hexametaphosphate solution were mixed. The component was then left in air for two hours at 1200 ° C burned. At the high temperature the marker appeared cherry red, at room temperature it turned buff Hs dark red and retained the color after several heating and cooling cycles that went up to 1000 ° C. It could no sign of peeling of the marking from the substrate can be found.

The component with the baked marking agent was then kept in boiling water for two hours and dried and baked again at 1000 ° C to examine the resistance of the marking agent. This treatment too was survived without damage.

Example 5

The suspension for the marking agent was in the same Prepared as in Example 1, with chromium trioxide and porcelain clay being mixed in a ratio of 1: 3. It was Fired in air at 1300 ° C for two hours. The marker on the support surface was dark green in color.

-6-

509837/0704

Any desired combination of metal oxides, depending on the color desired, but it is advantageous if refractory oxides are used. Metal oxides such as titanium oxide and / or aluminum oxide, although white, can be used to change the color of others To influence oxides, or even when white markings are needed.

Example 6

The marking agent was prepared in the manner of Example 1, with 98% by weight of Al-O and 2% by weight of porcelain clay or Bentonite mixed together and fired at 1600 ° C for two hours. The fired marker was white to cream-colored and was not affected by the subsequent tests.

From Example 3 it can be seen that soluble or insoluble components that provide the intended metal oxide when heated, can also be used. It should be emphasized at this point that it is advisable to use non-toxic oxides or Appropriate raw materials can be used. Organic solvents instead of water are used as the carrier liquid particularly useful where rapid drying is required.

Alternatively, temporary organic binders, such as alginates or, can also be added for lower temperatures Polyvinyl alcohol to make it easier to use and burn. Dispersants and stabilizers, like allomium polyelectrolyte or sodium hexametaphosphate,

7-

509837/0704

can be added to maintain the stability of the suspension for a longer period of time.

Another advantage of such "colors" according to Example 3 in The combination with silicon nitride is that they are liquid and they are very quickly absorbed by the silicon nitride. Depending on the viscosity of the paint, they penetrate to a certain extent into the silicon nitride. The abrasion resistance of silicon nitride is thus also transferred to the marking agent.

The marking agent is preferably applied to the silicon nitride applied by spraying from an aerosol container. However, other aids can be used for this purpose, e.g. a pen or a kind of pen holder, a kind of pillow, which is used alone or by means of a stencil, - to write letters, To generate numbers or the like. Stamp or similar.

Expectations:

5Q9837 / Ö7 (H.

Claims (12)

Expectations 1. A method for marking silicon nitride, characterized in that a mixture consisting of one Metal oxide and / or a raw material that provides a metal oxide when heated, a carrier liquid and a Binder on which silicon nitride is applied and the silicon nitride is then fired in the furnace. 2. The method according to claim 1, characterized in that more than one metal oxide or corresponding raw material is used in the mix. 3. The method according to claim 1 or 2, characterized in that the carrier liquid is water or an organic Liquid is. 4. The method according to any one of the preceding claims, characterized in that the binder is a refractory Contains binder. 5. The method according to claim 4, characterized in that the refractory binder is a silicate, oxide, nitride, alumina or glass. 6. The method according to any one of claims 1 to 3, characterized in that that the binder contains a temporary organic binder. 7. The method according to claim 6, characterized in that the binder is an alginate or polyvinyl alcohol. 509637/0704 8. The method according to any one of the preceding claims, characterized in that the silicon nitride prior to application of the Mixture is already burnt. 9. The method according to any one of the preceding claims, characterized in that the silicon nitride after application the mixture at a temperature between 600 C and 1600 C, preferably in the range around 1000 ° C, is fired. 10. The method according to any one of the preceding claims, characterized in that the silicon nitride after application the marking mixture is fired during its use. 11. The method according to any one of the preceding claims, characterized in that the metal oxide is iron oxide, cobalt oxide, Chromium trioxide, titanium oxide and aluminum oxide are used individually or in combination in the mixture. 12. The method according to any one of the preceding claims, characterized in that a raw material supplying the metal oxide is used Ferrous chloride or chromic anhydride containing raw material is used is. 509637/0704