Method of manufacturing aluminium nitride

The invention relates to a process for the preparation of Aluminum nitride, and in particular a process for preparing of solid aluminum or of Aluminiumnitridfa fibers, which allows a Nitrierungsumsetzung of Alu oxide easy to perform, which made it possible is solid aluminum or Aluminiumnitridfasern in high yield and to produce at low cost.

Aluminum nitride was used to prepare in a one to use resin sealant for semiconductor elements Filler or for producing a composite material thereof with any other type of metal used.

For the production of Aluminiumnitridfasern was in the Japanese Unexamined Patent Publication Hei / 2-300.319 proposed a method in which alumina fibers which 90 wt .-% or more of α-Al₂O₃ and less than 10 wt .-% SiO₂ include, in a mixed gas atmosphere, wel che ammonia and hydrocarbon gas comprises, at a Temperature of 1300 to 1700 ° C can be heat treated to thereby prepare Aluminiumnitridfasern.

According to this known method, however, was a suffi sponding Nitrierungsumsetzung of alumina at a Temperature of less than 1300 ° C or even at a hö hardly achieved heren temperature of not less than 1300 ° C will.

It was therefore necessary with this known method, the Nitrierungsumsetzung at a much higher temperature, which requires a longer time to carry out. If the Nitration reaction at such a high temperature and long period of time is carried out, it is unavoidable an increase in the cost of manufacture of the product bring.

Even if such a nitration reaction at such a high temperature carried out over a long period is, it is impossible to obtain a sufficient Nitrierungsumset To achieve tion of alumina and therefore it was Impossi sible to obtain Aluminiumnitridfasern whose nitration is degree of substantially 100%.

Japanese Unexamined Patent Publication Hei / 6-330.412 discloses a technique for the nitration of Oberflä che of alumina-silica fibers, in which the Alumina-silica fibers in a Mischgasatmo sphere which ammonia and a hydrocarbon gas to bordered, at a temperature of 1200 to 1600 ° C wärmebehan delt. With this prior art, however, it is impossible sufficient nitration to the middle or the Zen strand of the alumina-silica fibers to effect.

Accordingly, it is an object of the present invention, a process for producing an aluminum nitride solid easily manufactured in high yield, at the mixed gas or mixed gas or a gas mixture (Hereinafter referred to as a mixed gas), the or the at we sentlichen of ammonia gas and at least 0.5% by volume water hydrogen gas is, is produced, and then a solid γ-Al₂O₃, a precursor of γ-Al₂O₃ or a mixture of solid γ-Al₂O₃ and the aforementioned precursor in this Mixed gas heat treat at a temperature of 1200 to 1700 ° C These will.

Another Gege status of this invention is to provide a procedural ren for easily producing an aluminum solid to provide whose alumina content in we can be sentlichen completely nitrided in which a Mixed gas, which consists essentially of ammonia gas and little least is 0.5% by volume of a hydrocarbon gas, Herge will provide a solid and γ-Al₂O₃, a precursor of γ-Al₂O₃ or a mixture of the solid γ-Al₂O₃ and this before said precursor at a temperature from 300 to 1100 ° C is calcined in the above mixed gas and then in the above mixed gas at a temperature of 1200 to 1700 ° C is heat treated.

Another object of this invention is to provide a Ver drive for producing a Aluminiumnitridfaser to lie Far in the mixed gas, which consists essentially of Ammo niakgas and at least 0.5% by volume of a Kohlenwasserstoffga ses consists, is prepared, a liquid precursor of γ-Al₂O₃ is dispersed in an aqueous solution containing a Binder and a substance selected from the group is that of colloidal silica, colloidal Alumi oxide and colloidal zirconium dioxide, containing the aqueous solution containing the precursor dispersed therein ent is holding, focused, short fibers from the concentrated th aqueous solution in a centrifuge or cans spinning machine is introduced, by rotating the cans spinning machine woven, spun the short Fa fibers are dried, the dried short fibers at a temperature of 300 to 1100 ° C and calcined the calcined short fibers in the mixed gas in the we sentlichen from a hydrocarbon gas and ammonia gas is, at a temperature of 1200 to 1700 ° C heat treat are concerns.

A still further object of this invention is to provide a A process for the production of alumina fiber mats to supply, in which a mixed gas consisting essentially of Am moniakgas and at least 0.5% by volume of a hydrocarbon gas is, is produced, a liquid precursor is dispersed by γ-Al₂O₃ in an aqueous solution, wel che contains a binder and a material selected from the Group is selected from colloidal silicon dioxide colloidal alumina and colloidal zirconia be is, the aqueous solution containing the precursor therein disper will contain giert, focused, short fibers of the kon centered aqueous solution or in a centrifuge Cans spinning machine is introduced, by rotating the Do senspinnmaschine be spun, the woven short Fibers are dried, the dried short fibers at a temperature of 300 ° C to 1100 ° C calcined who formed to a mat with the calcined short fibers is and the mat in the mixed gas, which consists essentially of a hydrocarbon gas and ammonia gas is, at ei ner temperature is heat-treated from 1100 to 1700 ° C.

Further objects of this invention will become apparent from the following description.

<b>Fig.</b> 1 is a diagram illustrating both the X-ray diffraction chart of γ-alumina before Ni tration, which in the examples of this invention be used, as well as an X-ray diffraction chart of aluminum nitride, which according the invention are obtained, showing;

<b>Fig.</b> 2 is a diagram showing both an X-ray diffraction chart of γ-alumina precursor fibers before the nitration of this in the examples Invention can be used also as an X-ray diffraction pattern of the nitration of γ-alumina precursor fibers obtained aluminum umnitridfasern shows and

<b>Fig.</b> 3 is a diagram showing both an X-ray diffraction Diagram of aluminum oxide (a mixture of α-alumina and θ-alumina) which is not in this invention is used and an X-ray diffraction pattern of the above-mentioned Aluminiumoxi of which subjected to nitriding is showing.

The invention provides a process for the preparation of Aluminum nitride, which comprises a step of heat treatment of γ-Al₂O₃ or a precursor of γ-Al₂O₃ in a Mixed gas comprising, consisting essentially of a Kohlenwas hydrogen gas and ammonia gas.

As used herein, "precursor of γ-Al₂O₃ '' should a substance prior to its conversion to γ-Al₂O₃ or when this substance previously at a temperature of 1000 to 1100 ° C is heat-treated, a gelled substance was before ner conversion to γ-Al₂O₃ mean.

The γ-Al₂O₃, by thermal decomposition of an organic or inorganic compound can be prepared. Examples of an organic or inorganic aluminum connection are aluminum alkoxide, aluminum sulfate, Alumi niumalaun or potassium aluminum sulfate, Ammoniumaluminiumcar carbonate and Aluminiumhydroxichlorid. This Aluminiumverbin compounds are specific examples of the precursor of γ-Al₂O₃.

Furthermore, the term used herein "a festival body of γ-Al₂O₃ or precursor thereof "particles or mean flakes of γ-Al₂O₃ or the precursor thereof.

After extensive investigations by the inventors regard the conventional production method for aluminum nitride was found that for nitration of Aluminiu Moxide required reaction temperature and time greatly in Depending on the types of the nitration reaction to verwendendem Rohaluminiumoxidmaterial varies.

For example, when the nitration reaction α-Alumi oxide or δ-alumina as Rohaluminiumoxidmaterial is used, a reaction temperature of more than 1500 ° C and a reaction time of not less than 5 Hours required. Furthermore, it is even if the Heat treatment at this high temperature and for this long period of time is performed, hardly possible that crude luminiumoxidmaterial substantially completely nitrie ren.

If γ-Al₂O₃ is used as Rohaluminiumoxidmaterial, the required for the nitration reac tion temperature are significantly reduced and at the same The response time can be greatly reduced.

The inventors have found that the reason for the inherent high specific surface area of ​​γ-Al₂O₃ can be attributed.

It has been found that the specific surface of γ-Al₂O₃ is about 10 times as large as that of α-Al₂O₃, so that when ammonia gas with this large specific surface area of ​​γ-Al₂O₃ is brought into contact, the Nitrie extension reaction of γ-Al₂O₃ promoted excellent can.

It has been found that in the method for producing caused by γ-Al₂O₃ a, significant dehydration is, where a large number of fine pores of from 10 to 100 angstroms in diameter in the particles of γ-Al₂O₃ to be left behind, so that the specific surface area of γ-Al₂O₃ is increased. If this γ-Al₂O₃ further heated is, it is converted to α-Al₂O₃, at the same time a large number of fine pores is lost and so the specific surface area of ​​γ-Al₂O₃ decreases drastically.

In this invention, γ-Al₂O₃ with a large number fei ner pores and a very high surface area above it clarifies contemplated and for increasing the Nitrie addition reaction in the production of aluminum via a method of contacting γ-Al₂O₃ with a Mixed gas consisting essentially of a hydrocarbon gas and ammonia gas is used.

As in this invention to be used γ-Al₂O₃ is the γ-Al₂O₃ used, the egg through the thermal decomposition ner organic or inorganic aluminum compound or all types of precursors thereof is obtained. Insbesonde re is the γ-Al₂O₃ that of thermal decomposition Aluminiumhydroxichlorid as alumina source or formed by this precursor Aluminiumhydroxichlorid can be obtained, more preferably in this invention as a γ-Al₂O₃ or the precursor thereof is used, since these Compounds and a highly reactive nitrogen from have drawn formability.

The mechanism of thermal decomposition of aluminum umhydroxichlorids can be represented as follows:

As can be seen from the above table, is, when the Aluminiumhydroxichlorid at a temperature of 300 to 400 ° C is heated in the Aluminiumhydroxichlorid an alumina (Al₂O₃ · H₂O) converted with HCl and H₂O is deposited. If this alumina hydrate is further heated to 600 to 700 ° C, it will γ-Al₂O₃ converted with separation of H₂O. If this γ-Al₂O₃ is further heated to 1200 ° C or more, it is to α-Al₂O₃ converted.

As explained above, the production of this is Zwischenpro adduct of γ-Al₂O₃ by the release of H₂O and HCl gas accompanied, what of the formation of a large number Pores in the γ-Al₂O₃ results, whereby a large speci fish surface of the γ-Al₂O₃ is generated.

If this γ-Al₂O₃ as it is or after calcined has, at a temperature from 300 to 1100 ° C in egg ner mixed gas atmosphere consisting essentially of ammonia gas be and at least 0.5% by volume of a hydrocarbon gas stands, is heat-treated, it can easily in a aluminum nitride are converted.

In this reaction, γ-Al₂O₃ by ammonia gas is redu sheet where aluminum is produced. One of Nitrie extension reaction to be throwing raw material may γ-Al₂O₃ per se, or a precursor of γ-Al₂O₃, which in γ-Al₂O₃ can be converted, when it reaches 1000 to 1100 ° C the reaction of the formation of aluminum nitride is heated.

The reason for limiting the content of hydrocarbon hydrogen gas at not less than 0.5 vol% in the material gas, the nitration reaction is to be supplied, the fol lowing. When the content of the hydrocarbon gas less than 0.5% by volume, the partial pressure of hydrocarbon can be hydrogen gas sufficiently, so that the rate of Nitration reaction of γ-Al₂O₃ be extremely slow can. The hydrocarbon gas is used to remove it zeugtem H₂O from the reaction between γ-alumina, and Ammonia. In terms of suppressing the generation an extensive amount of carbon, the content should be at Hydrocarbon gas preferably to not more than 20% by volume be adjusted. As the hydrocarbon gas, propane gas, methane gas, ethane gas and butane are used. However, propane is the preferred, since it cost obtainable.

The nitration reaction is conducted at a heating temperature of 1200 to 1700 ° C. If this heating temperature we niger is over 1200 ° C, the reaction rate is too slow, so that it requires a long period of time and simultaneously, it would hardly be possible, the nitration of γ-Al₂O₃ to fully achieve. Respect to the upper Limit of the heating temperature, although a temperature of 1460 ° C to achieve complete Nitrierungsreak tion may be sufficient, a higher temperature than 1460 ° C with a view to accelerating the implementation be used. A heating temperature of greater than 1700 ° C is not preferred because it to increase the manufacturing lead free. Therefore, the preferred range for the Heating temperature of 1300 ° C to 1460 ° C.

According to this invention, it is also possible Aluminiumni tridfasern using γ-Al₂O₃ fibers as Rohalu miniumoxidmaterial that is to nitride to produce. In this case is also a first mixed gas in the be essentially of hydrocarbon gas and ammonia gas is, as mentioned above. The starting material for alumina, a liquid precursor of γ-Al₂O₃ be used. As mentioned above, the precursor should of γ-Al₂O₃ preferably wholly or partly made of aluminum hydroxichlorid exist.

This liquid precursor is in an aqueous solution dispersed, containing a substance from the group is selected from colloidal silica, kolloi dalem alumina and colloidal zirconium dioxide, to obtain a dispersion. Colloidal silica, colloidal alumina, and colloidal zirconia, we ken respectively as a binder for joining γ-Al₂O₃-part chen among themselves. In addition to these binders may Another binder for spinning, such as polyvinyl alcohol, be added.

The dispersion thus obtained is then reacted with a rotary evaporator concentrated to a viscous, gel-like Materi al to obtain. The viscosity of this gel-like material may generally be about 30 poise. This viscous Solution in a centrifuge or cans spinning machine introduced, with on the outer peripheral wall of a large KISSING number of fine openings is provided and thereafter the doses spinning machine in a with dry at 100 ° C heated, hot air filled chamber rotates. in the result nis the viscous solution of these fine holes, consisting in the outer peripheral wall of the cans spinning machine formed, extruded out, with short fibers produced will. The surfaces of these as-spun short fibers are then directly by the hot air in the chamber dried. Subsequently, the short fibers are completeness dig, including the core areas of the fibers, getrock net, to thereby obtain ordinary short fibers.

Subsequently, the short fibers are collected and egg ner temperature of 300 to 1100 ° C calcined, said Peek term components, such as H₂O or HCl, the ge the precursor were collected, be removed. When the temperature of Kal zinierung is less than 300 ° C, the calcination are not completed. On the other hand, the Tempe exceeds temperature calcination to 1100 ° C, the pre might runner be converted to α-Al₂O₃ on γ-Al₂O₃. The so calcined precursor (short fibers) is then present in the mentioned mixed gas, which consists essentially of hydrocarbon hydrogen gas and ammonia gas is, at a temperature of 1200 to 1700 ° C heat-treated, whereby the nitration of the short fibers is completed.

Even in the production of it is Aluminiumnitridfasern preferable, one or more kinds of hydrocarbon gases from propane, methane gas, ethane gas and butane gas from to choose.

The heating temperature in the nitration reaction to the case, preferably in the range of 1300 ° C to 1400 ° C as in the case of preparing the above-mentioned aluminum nitride solid lie.

It is also possible to provide a mat using the vorer produce mentioned method, wherein the short fibers just as, from a large number of fine openings which are formed in the outer wall of the can end spinning machine, are extruded, are collected to a mat he witness. In this case, the mat is at a temperature calcined from 300 to 1100 ° C and then in a mixed Gas, which consists essentially of hydrocarbon gas and Ammo niakgas is, heat treated to a from Aluminiumni tridfasern composite mat to produce.

Even in the preparation of one of an aluminum nitride fiber composite mat, it is preferable to use a or more kinds of hydrocarbon gases from propane gas, methane gas, ethane gas and butane select.

The when the heat treatment of the calcined short Heiztempera fiber composite mat to be used temperature should preferably be in the range of from 1300 ° C to 1460 ° C, as in the case of the aforementioned aluminum nitride solid lie.

example 1

A γ-Al₂O₃ powder (trade name: AKP-G015, aver cher particle diameter: 0.1 μms available from Sumitomo Kagaku Co.) was in air at a temperature of 900 ° C for 2 calcined hours. The thus calcined γ-Al₂O₃ powder was then in mixed gas, which consists essentially of 5% by volume propane and ammonia gas is at a temperature of 1400 ° C for 1 Hour heat-treated to the nitration of the γ-Al₂O₃ powder perform.

If so nitrided γ-Al₂O₃ powder X-ray diffraction was investigated, the complete nitration was the γ-Al₂O₃ powder confirmed. If the so-nitrided γ Al₂O₃- Powder was observed by an electron microscope, Wageningen de found for the diameter of the powder that he always is still only 0.1 microns or less. <b>Fig.</b> 1 shows a X-ray diffraction pattern of product obtained in this example Aluminum nitride.

example 2

To 3200 g of a solution of Aluminiumhydroxichlorid (the Ge stop at Al therein was 3.5 wt .-%, calculated as Al₂O₃) was a 10 wt .-% of concentrated 697 g. polyvinyl alcohol and 116 of a 20 wt .-% conc. colloidal silica added to obtain a mixed solution. After this This mixed solution was stirring using a Rotary evaporator concentrated to a gel-like Mate rial having a viscosity of 35 poise at a temperature to obtain from 20 ° C (a precursor of γ-Al₂O₃).

This viscous liquid was applied to one at a Rotati onsgeschwindigkeit of 1000 U / min in a with dry Air-filled chamber rotating disk dropped. In It result was the so dripped liquid immediately in the form distributed by the wheels and by the centrifugal force of the Disc blown away, where small particles were formed. These particles were collected and at a temperature dried at 100 ° C. When these dried particles were examined by an electron microscope, was found the particles have a flaky shape of about 5 microns thickness and 10 to 50 microns width and length.

Then, this flaky γ-Al₂O₃ particles were in the air at a temperature of 900 ° C for 2 hours in the same Way calcined as in Example. 1 Thereafter, the so calcined flaky γ-Al₂O₃ particles as in the case of Example 1 in the mixed gas, which consists essentially of 5 vol% propane and ammonia gas is at a Tempe temperature of 1400 ° C for 1 hour heat-treated to the nitration perform the γ-Al₂O₃ powder. As a result, were flakes obtained from aluminum.

Example 3 and Comparative Example 1

To 3200 g of a solution of Aluminiumhydroxichlorid (the Ge halt of aluminum therein was 23.5 wt .-%, calculated as Al₂O₃) were concentrated 697 g of a 10 wt .-%. Polyvinalalkohol solution and 116 g of a 20 wt .-% conc. colloidal Silici umdioxids added to obtain a mixed solution.

After stirring this mixed solution was USAGE tion of a rotary evaporator concentrated to a gelar term material having a viscosity of 35 poise at a to obtain temperature of 25 ° C (a precursor of γ-Al₂O₃).

This viscous liquid or in a centrifuge Cans spinning machine with a length of 600 mm, a through diameter of 200 mm is inserted, on the outer circumference wall with a large number of small holes each having is provided a diameter of 0.5 mm. This Spinnma machine was operated at a rotation speed of 2000 U / min in a rotating chamber, the ge with dry air is filled with the viscous fluid of the in outer circumferential wall of the spinning machine formed small Openings is extruded to obtain short fibers. After drying at a high temperature in the chamber WUR collected to these fibers and at a temperature 900 ° C for 2 hours to obtain short fibers of γ-Al₂O₃ calcined. These short fibers were then in mixed gas, consisting essentially of propane and ammonia gas, heat-treated at a temperature of 1400 ° C for 1 hour, wherein the content of the propane gas in the mixed gas various is amended dentlich wherein Aluminiumnitridfasern Sustainer th be.

On examination of the thus obtained crystalline phase of Aluminiumnitridfasern by X-ray diffraction were the Sustainer in Table 1 (Nos. 1 to no. 5) obtained results th.

The crystalline phase of Aluminiumnitridfasern which the Nitriding treatment without introducing propane into the Gas atmosphere (no. 1) was subjected and the kri -crystalline phase of Aluminiumnitridfasern which the Ni tration treatment in the gas atmosphere in which the Content of propane to less than the through this inven tion defined lower limit was lowered (no. 2) under was discarded, also as comparative examples in this Table 1.

<imgref idrefs="16/1" />Table 1

<imgref idrefs="16/1" />Modification of the crystalline phase of AlN, depending on the content of LP Gas

example 4

The from the sample no. 5 in Example 3 (Table 1) get NEN short fibers of γ-Al₂O₃ were to form a Mat te of 40 mm width, 100 mm length and 25 mm thickness GESAM melt. This mat was made of 94 wt .-% fibers and the residual ei ner mixture of particles and flakes composed where from both a size of less than 0.5 mm (mesh) have.

6 pieces of mat were prepared and they were about 3 Couples separated. These pairs of mats were heat treatment at a temperature of 300 ° C, 650 ° C or 800 ° C subjected for 30 minutes to 3 types of calcined mats were obtained. was for each of the calcined mats ge found that it is amorphous and the specific surface of fibers forming these calcined mats, was 54.2 m² / g.

Each pair of boots was further 30 minutes heat treat air at a temperature of 1000 ° C or 1100 ° C concerns. In the examination of the resulting mats was found for each of them by X-ray diffraction that they have been converted to γ-Al₂O₃, so as to Her provision of aluminum nitride by nitration were suitable.

Then this calcined mats a Nitrierungsbe were action subject. The nitriding treatment was carried Introducing the calcined mats in an alumina ship and then by heat treating the calcined Mat th in a mixed gas atmosphere containing 3 vol% of propane and comprising the remainder of ammonia gas, at a temperature of 1200-1400 ° C heat-treated for 3 hours.

Thereafter, these nitrided mats a Entcarbonisie were tion treatment by their further heating at a Tem subjected to temperature of 700 ° C for 5 hours. The resultie -generating mats were in their composition with means XRD investigated. The results are in Ta belle 2 as no. 6 to no. 11.

As is clear from Table 2, found in all of the GE according to no. 6 to no. 11 obtained mats the formation of AlN instead of. <b>Fig.</b> 2 shows diagrams of the X-ray diffraction of the mat No. 9 before the nitriding treatment and after calcining at 650 ° C and the mat, which was nitrided.

Example 5 and Comparative Example 2

The short fibers of γ-Al₂O₃, which in the same manner obtained as in the case of no. 5 in Example 3 (Table 1) were, were calcined to obtain γ-Al₂O₃ fibers.

The γ-Al₂O₃ fibers were then in a mixed gas stream that 2 vol% propane and the residual ammonia gas includes, among along with various change in the temperature of the heat treat ment to give Aluminiumnitridfasern heat treated.

The crystalline phase of thus obtained Aluminiumnitridfa fibers was studied by X-ray diffraction, and the content of oxygen in the fibers was measured using a Oxygen / nitrogen Simultananalysators measured. Which he preserved results are shown in Table 3 together with Ver same examples (Nos. 12 to no. 13) is shown.

<imgref idrefs="20/1" />Table 3

<imgref idrefs="20/1" />Relationship between nitriding and Content of O₂ in AlN fibers

As can be seen from Table 3, factory it is Lich, the nitriding treatment of γ-Al₂O₃ with a Tem perform temperature of not less than 1200 ° C. If namely the nitriding treatment of γ-Al₂O₃ at a Temperature is carried out of not less than 1200 ° C, , the content of oxygen in the resulting Alumi niumnitridfasern be reduced. If the content of Oxygen in the fibers is high, the Wärmeleitfä ability of the fibers to undesirably. The Ni tration treatment at a temperature of not less than 1400 ° C is particularly in view of the minimization of the oxygen content is preferable in the fibers.

In the comparative examples (Nos. 12 to no. 13) was the Temperature for the nitriding treatment 1000 ° C or 1100 ° C, so that the Aluminiumnitriderzeugung failed and simultaneously a high oxygen content, ie 23% by volume and 34% by volume, showed in the fibers.

That in no. 14 to no. 18 obtained in Example 5 aluminum nitride and the in Comparative Examples (Nos. 12 to Nr. 13) with respect to the products obtained was Nitrie tion degree measured using a thermobalance. Table 4 shows the results obtained. As Table refer 4, all of this invention show under it preserved Aluminiumnitridproben a nitration of 100%.

<imgref idrefs="21/1" />Table 4

<imgref idrefs="21/1" />Relationship between nitriding and nitration *

example 6

The in in the same manner as in the case of Sample Nos. 5 Example 3 (Table 1) obtained short fibers of γ-Al₂O₃ were calcined to obtain γ-Al₂O₃ fibers.

The γ-Al₂O₃ fibers were then in four different ways from mixed gas streams, each of which consists essentially of Ammo niakgas and 2% by volume of methane gas, ethane gas, propane or Butane gas is at a temperature of 1400 ° C while one hour, heat-treated in order to Aluminiumnitridfasern receive.

The crystalline phase of the resulting Aluminiumnitridfa fibers was studied by X-ray diffraction. The get NEN results are shown in Table 5 (no. 19 to no. 22) ge shows.

<imgref idrefs="22/1" />Table 5

<imgref idrefs="22/1" />Relationship between types of hydrocarbon gas and crystalline phase of nitrided fibers

As can be seen from Table 5, we could not sential difference in the crystalline phase this Aluminiumnitridfasern regardless of the difference determined the types of hydrocarbon used will. Therefore, the use of propane is preferred because it is the cheapest.

example 7

The in in the same manner as in the case of Sample Nos. 5 Example 3 (Table 1) obtained short fibers of γ-Al₂O₃ were different change of Kalzinierungstem temperature ge in the range of 300 to 1000 ° C, as shown in Table 6 shows calcined.

The calcined short fibers were then mixed in a gas stream consisting essentially of 2% by volume of propane gas and the Residual ammonia gas is at a temperature of 1400 ° C would for one hour to give Aluminiumnitridfasern mebehandelt.

The crystalline phase of the resulting Aluminiumnitridfa fibers was studied by X-ray diffraction and was then the content of oxygen in the fibers by using egg nes oxygen / nitrogen Simultananalysators measured. The Results obtained are shown in Table 6 below.

<imgref idrefs="24/1" />Table 6

<imgref idrefs="24/1" />Relationship between calcination and oxygen content in the AlN fibers

As Table 6 it can be seen, we could not sential difference of the crystalline phase of aluminum umnitridfasern be found as long as the Kalzinie annealing temperature be in the range of 300 to 1000 ° C was selected. However, what the content of oxygen in the Aluminiumnitridfasern relates applies, could the higher the Calcination temperature was so low, the content of Oxygen are set in the Aluminiumnitridfasern.

As a sample of Comparative Example (no. 27), the sliding chen fibers such as those of the above example at a Tempe temperature of 1300 ° C calcined, to obtain found that the resulting fibers from a mixture of α-Al₂O₃ and θ-Al₂O₃ were composed. When the fiber a nitriding treatment at the same temperature and Be subjected to treatment time as those of the above example were were the fibers and of a mixture of α-Al₂O₃ AlN composed. <b>Fig.</b> 3 shows a diagram of a Rönt diffraction studies, as at one before nitriding obtained calcined product and the after Nitrie tion treatment resulting nitrided product obtained WUR de.

example 8

To 3200 g of a solution of Aluminiumhydroxichlorid (the Ge stop at Al therein was 23.5 wt .-%, calculated as Al₂O₃) were 10 percent .-% conc 697 g. polyvinyl alcohol and 200 g of 18 wt .-% conc. colloidal silica added, to obtain a mixed solution. After stirring was this mixed solution using a Rotationsver evaporator concentrated to a gel-like material having a Viscosity of 35 poise at a temperature of 20 ° C to get (a precursor of γ-Al₂O₃).

The viscous liquid was prepared in the same manner as in Example 3 spun to obtain short fibers.

The short fibers were then mixed in gas in wesentli chen from 2 vol% propane and ammonia gas is, at ei ner temperature of 1450 ° C for 2 hours to obtain Alumi niumnitridfasern heat treated. If the crystalline phase of thus obtained Aluminiumnitridfasern by Röntgenbeu tion was examined, only the AlN phase was noticed will.

The fibers thus obtained had a more or less lower elasticity in comparison with that in the Nos. 3 to no. 5 obtained from Example 3 fibers.

The same procedure as illustrated above is, was repeated, except that 100 g of 10 wt .-% conc. colloidal zirconia instead of 18 wt .-% conc. colloidal silica was used and the Ni tration temperature 1350 ° C was in place from 1450 ° C to obtain Aluminiumnitridfasern. If the crystalline Phase of the resulting Aluminiumnitridfasern by Rönt diffraction studies were examined, only the AlN phase was fixed be provided.

For the fibers thus obtained was found to have a more or less shorter fiber length in comparison with that comprise of fibers using the aforementioned colloidal alumina, or those who in no. 3 obtained to no. 5 of Example 3 fibers.

example 9

In the same manner as explained in Example 3, short fibers which 97 wt .-% Al₂O₃ and 3 wt .-% SiO₂ in order grasp, spun. After calcination in air atmosphere at a temperature of 650 ° C for 30 minutes, 200 g of the resulting calcined fibers in 200 liters of water colloidal together with 15 g of soluble starch and 50 g Si dioxide dispersed, both of which as a binder ver be used, and the resulting mixture was fully continuously stirred to obtain a slurry.

A mold for vacuum forming was ge in this slurry immersed and the interior of the mold was sucked so that the fibers and binder in the slurry at the may adhere to the surface of the mold to such a shaped of product. The molded product was then entwäs sert and dried. As a result, a panel of 150 was mm length and width, 20 mm in thickness and 0.2 g / cc bulk or obtained density. The panel was then placed in an electric oven and introduced kalzi at a temperature of 600 ° C ned. After this panel was in the oven in a Ammo niakgasatmosphäre containing 3% by volume of LPG, in a Temperature of 1200 ° C for 3 hours to obtain an aluminum miniumnitridtafel heat treated.

The panel thus obtained showed a high mechanical Festig ness. After at a decarbonization was subjected to a temperature of 700 ° C for 5 hours, , the resulting sheet by X-ray diffraction examined, it was being found that the formation of AlN has taken place in the panel.