DE1189056B - Process for the production of titanium diboride - Google Patents

Description

Process for Making Titanium Diboride The invention relates to the production of titanium diboride through the well-known high-temperature reaction of titanium dioxide, Boron oxide and carbon.

The reaction by which the method works can be made by the following Equation can be shown: TiO2 -I- 5 C -I- B203 = TiB2 -I- 5 CO The reaction is carried out in a known manner at a temperature of about 1350 ° C and higher. In practice it is more advantageous to work at higher temperatures, e.g. B. up to about 2000 ° C. Suitable ovens in which the reaction can be carried out, the usually have a graphite tube as a reaction space are expensive Construction and operation, and it is important to use the thermal energy as possible to exploit economically. Since the reaction is endothermic, this is the achievement Profitability difficult.

The arrangement of the reactants in a boat or box leads to significant heat loss. Another known way of working is in the furnace a larger amount of material in the form of a body made by heating a mixture of boron oxide, titanium dioxide, carbon and molasses or other carbonaceous Binder, used and thus a reduction in heat losses compared a reaction mixture in a boat or box. But also on this way or when using solid cylindrical pieces as feedstock as a result of the endothermic reaction, optimal heat utilization is not obtained.

It has been found that by using specially shaped bodies a more efficient heat transfer from the furnace to the briquettes is achieved, whereby in a given furnace the throughput can be increased. Such moldings from reaction mixture can be tubular, cross-shaped, star-shaped or semicircular, optionally corrugated. For ease of handling and manufacture, tubular pieces are preferred.

The invention thus relates to a method for producing titanium diboride by heating moldings from an intimate mixture of boron oxide and carbon and titanium dioxide to a temperature above 1350 ° C and is characterized by that one uses such a molding in which the ratio of the surface to the volume of the solid at least 1.5 times, preferably 2.5 times, of a solid cylinder of the same length and diameter. Preferred is a molding with a longitudinal bore, the wall thicknesses being advantageous are the same, for example when the body is cylindrical and the bore is cylindrical and is coaxial.

The preferred method of making the moldings used in the process according to the invention consists in that a mixture of carbon, Titanium dioxide and boron oxide extruded or otherwise into the desired shape and heated to a temperature above the softening temperature of boron oxide, whereupon the molded product is cooled. Boron oxide then forms a glassy one Base for the carbon and titanium dioxide particles. Of course you can one also use bodies made in a known manner with the help of molasses or others Carbohydrate binders were made. Boron oxide can be used in a known manner replace completely or partially with a substance that produces boron oxide when heated, for example boric acid; however, this substance must be converted to boron oxide before the body to the necessary for the formation of titanium diboride Temperatures is heated. In general, this transformation takes place during the production of the molded articles instead of. For the sake of brevity, only boron oxide is spoken of in the following.

In the production of the moldings, an intimate mixture of the Heat ingredients in a mold with the desired dimensions to a temperature, which is sufficient to convert boron oxide into a glassy phase. This temperature is between 300 and 1000 ° C, but is preferably 400 to 500 ° C, in particular 460 ° C. If boric acid is used, it is heated to this temperature dehydrated to boron oxide. While boron oxide is converted into a glass phase, can A pressure can be applied in the longitudinal direction to give the body a higher density to lend, e.g. B. at least 1.1 g / cc, preferably at least 1.4 g / cc. is When the heat treatment is finished, the molding is removed from the mold.

If a molding with a longitudinal bore is desired, a pointed cylindrical or differently shaped rod or mandrel can be pressed into the molding produced in the same way, while it is firmly enclosed, preferably in the mold. This is expediently carried out at a temperature at which the material of the molding is more or less plastic, but without flowing, preferably at a temperature between 400 and 800 1 C.

One can also enclose the material in the longitudinal direction, e.g. B. by closing the mold on one side or the other with a washer, which is equipped with a hole for the passage of the mandrel. It was found, that a mandrel with a diameter of up to two thirds of the molding can be used can. This way you can't just drill a hole while maintaining an adequate one mechanical stability of the molding, but you can also use it Obtain high density bodies.

Titanium dioxide can be used as rutile, but preferably in the form of anatas. The preferred carbon is graphite, but you can also use soot or carbon in another form; it may then be necessary use an inert atmosphere or lower temperatures to prevent oxidation of the Avoid carbon in the manufacture of the moldings.

Boron oxide can be calculated in excess in the molding in a known manner on titanium dioxide. For example, there is an excess of up to 50 percent by weight permissible, but not more than 5 to 10 percent by weight is preferred. A minor one An excess of carbon is advantageous, but it should not be 5 percent by weight exceed and is preferably 1 to 3 percent by weight.

It is important that the substances used for molding production are intimately mixed, otherwise you will not get good results. A mix in a ball mill gives a satisfactory mass.

According to the process according to the invention for the production of titanium diboride the briquettes are heated to a temperature above 1350 ° C, in particular 1550 to 2000 ° C, heated. An inert gas, e.g. B. argon, to dissipate the forming Use carbon monoxide. However, it is preferred to carry out the reaction at one temperature above 1550 ° C, preferably above 1700 ° C, in a carbon monoxide atmosphere and deter the product asap.

The invention is illustrated by the following examples.

Example 1 An intimate mixture of graphite, Boric acid and anatase produced with a grain size below 0.08 mm, namely with a graphite excess of 111 / o and a boric acid excess of 1511 / o over the stoichiometric amounts.

The mixture, made into a paste with about 8% water, was poured into a steel pipe filled with a clearance of 3.2 cm and the tube in an oven to 450 ° C Heated for 1 hour to dehydrate the boric acid. After that, the steel pipe with the dehydrated mixture taken out of the oven and the hot mixture in the Tube with the aid of a press ram that fits loosely in the tube under a pressure of 14.1 kg / em2 pressed. The molding thus formed was squeezed out of the tube and could cool down. The density was 1.6 g / cm3. The length was now 22.9 cm.

A 2.03 twist drill was used to drill a drilled hole of the same size.

The formation of titanium diboride was carried out in an electric furnace with a Graphite tube made as a reaction space (3.8 cm clear width). The molding became heated in an inert atmosphere at 1910 ° C for 9 minutes, whereupon the product moved into a colder part of the oven. The product was a crumbly one gray powder with 98.211 / o TiB2.

A similar molding with a density of 1.6 g / cm3, but without Bore, took 29 minutes to react at the same temperature. Example 2 A damp mixture of boric acid, titanium dioxide and graphite was placed in a tube with 5.1 cm3 clear width and heated to 450 ° C for 11/4 hours to get accordingly Example l to dehydrate the boric acid.

In this way, a molding having a density of 0.78 was obtained g / cm3. It was pushed out of the pipe and while still hot in a preheated split Shaped tube with 5.1 cm clear width inserted and then a steel mandrel with the largest Shank thickness of 3.8 cm axially into the molding under a load of 226.8 kg inserted. The mandrel was pulled out and the piece of pipe by opening the mold taken out. The molding had a density of 1.6 g / cm3 and a length of 22.9 cm.

Titanium diboride was produced from this molding by heating in an electric furnace in an inert atmosphere in a graphite tube with 6.4 cm lights Distance, namely 11 minutes at 1940 ° C; then he was in a colder area of the oven pushed. The product was a crumbly gray powder with 97.511 / o TiB2.

A molding of the same dimensions, but without a hole, with a Density of 9.79 g / cm3 required 40 minutes for the reaction at 1940 ° C.

Claims (4)

Claims: 1. Process for the production of titanium diboride by Heating a molding made from an intimate mixture of boron oxide, carbon and Titanium dioxide at a temperature of over 1350 ° C, characterized in that one such a molding is used in which the ratio of surface area to solid volume at least 1.5 times, preferably 2.5 times, a solid cylinder of the same Length and the same diameter. 2. The method according to claim 1, characterized in that that one uses tubular, preferably cylindrical body with a coaxial bore. 3. The method according to claim 1 and 2, characterized in that one is a molding used by forming an intimate mixture of boron oxide, titanium dioxide and Carbon and heating this mass to a temperature above the softening temperature of boron oxide has been produced. 4. The method according to claim 3, characterized in that that one uses a tubular molding, which by drilling a mandrel in the mass, which has become plastic through heating, is produced in a closing mold has been.