CS274076B1 - Method of powders preparation for non-oxide and oxide nnitride ceramics production - Google Patents

Abstract

The invention concerns a method of production of nitrides or oxide nitrides including sialones or carbides of silica and/or aluminium, zirconium and titanium from oxide raw materials or from metal powders in the presence of compounds of iron as catalysts in a quantity of 0.l to 10 % by weight expressed as iron oxide, by firing at 800 to 1600 degrees C for 0.5 to 12 hours with a constant flow of nitration and/or protective gas with occurrence of a product which is modified by grinding to a particle granularity of 0.01 to 5 μm. The essence of the invention is that the powdered product in the form of a suspension in liquid is magnetically separated at a field intensity of 0.05 to 1 T and the low-ferric non-magnetic fraction is a withdrawn from the magnetic fraction. The separated magnetic fraction of powder can be used as an intensifying additive from the raw mixture.

Description

(57) Solution ea relates to a process for the preparation of nitrides or oxinitrides including isialones or silicon and / or aluminum carbides, zirconium, titanium from oxide raw materials or metal powders in the presence of iron compounds as catalyst in an amount of 0.1 to 10% by weight. expressed as iron oxide, by firing at 800 to 1600 ° C for 0.5 to 12 hours at a steady flow of nitriding and / or shielding gas to give a product which is adjusted by grinding to a particle fineness of 0.01 to 5 nm. The essence of the solution is that the powder product in the form of euepension in the liquid is magnetically separated at a pols intensity of 0.05 to IT and the non-magnetic low-iron fraction is separated from the magnetic fraction. The removed magnetic portion of the powder can be used as an intensifying additive from the feedstock mixture.

CS 274076 Bl * (CS 274076 Bl • b

The invention relates to the field of the preparation of powders for the production of ceramics based on one or more elements of the Si, Al, Ti and Zr groups,

The preparation of nitrides, oxinitrides, including aialones, carbides by the powder metal nitriding method or the reducing nitriding method of finely divided oxides, a mixture thereof or a mixture thereof with nitrides, is generally known. The disadvantages of these processes are also known. One of them is that nitrous resp. The reduction and nitride reaction of the pure substances proceeds at a relatively low rate. The impurity purity of the starting materials guarantees a minimum amount of undesirable melt in the Ayatema. The acceleration of the synthesis can be achieved by admixtures or additives of catalysts, in particular iron compounds. Their presence ¹ in powdered products may destroy important quality parameters of the final steel products, such as. resistance to oxidation at high and high temperatures, which has lowered resistance to deformation in the glans. The presence of iron compounds further contributes to an increase in the proportion of melt and hence the vitreous phase in the final product.

The aforementioned disadvantages of au have been largely rewarded by the proposed adaptation and apoaob of preparation. Based on the study of zrnion apóaobu binding of iron compounds in reducing and nitrous furnace environments, the possibility of deliberate utilization of direct admixtures has emerged. 1 and f) J.oloan n / noblo lob addition to the ureaolilonium oynthes of carbides, nitrides and oxides, including aialones of Si, Al, Ti and Zr elements; The principle is that the synthesized and finely ground powder is separated in the next step in the form of a suspension on a magnetic sludge aeparator. or by separating the solid particles from the suspension by conventional techniques. The dried powder is used for further processing. The non-magnetic fraction serves as a semi-product for the manufacture of structural ceramics and the magnetic fraction is used as an additive in the preparation of the feedstock mixture prior to synthesis.

This additive performs two functions. Reaction catalyst puncture in the synthesis due to a sufficiently high content of iron compounds and the deleterious function of the nuclear additive i.e. the seeds of the desired non-oxide or oxinitride phase formed. The combined catalytic and nucleation effect aa achieves an acceleration of the synthesis progress, with subsequent magnetic separation substantially reducing the iron content prior to the final compaction step of the products.

The example of aielone aynthesis further elucidates the nature of apoaob without, however, limiting the scope of the claim to these examples.

i) ·

Claims (2)

Example 1 - Synthesis of Eialone Powder -h 79% wt. % of dry kaolin e 21 wt. The soot was prepared in the form of granules (3 x 5 mm) without the addition of iron compounds (mixture A). Fe3 O4, expressed on annealed condition. In a similarly prepared second mixture aa, iron in the form of ferric hydroxide (mixture B) was added, and to another mixture ea, a magnetic portion was added after mixture B (mixture C) was separated. Synthesis of aialon in a flow-through graphite reactor, with a nitrogen flow rate of 0.02 m ^-min ^-1 . kg ^{-1 of the} batch at 1450 ° C was carried out for 2 hours. The product was milled in an aqueous-alkaline (95 + 5) medium and magnetically separated on a tester at 0.4 T. >? CS 274076 Bl Comparison of results from individual mixtures: Procedure parameter unit % By weight. mixture A mixture B mixture C 1. Raw material conversion to sialon 68 82 96 2. Content of iron compounds in the synthesis product SSítejO ^ 1.2 8.5 8.1 3. Non-magnetic fraction of product % 70 55 59 4. Iron content in non-magnetic fraction SSFegO-j 0.30 0.51 0.49 5. Magnetic fraction of product % 30 45 41 6. Iron content in magnesium % Fe ₂ 0j 3.3 18.3 19.1 share The low iron content of the meshes in the non-magnetic fraction enables its use for construction purposes. The magnetic fraction is partially / e.g. 25% w / w is reused in the feedstock as a catalyst and nucleator and the remainder can be used for products intended for less demanding operating environments. OBJECT OF THE INVENTION 1. Process for preparing powders for the production of non-oxide and oxinitride ceramics from oxide raw materials or metal powders in the presence of iron compounds as catalyst in an amount of 0.1 to 10% by weight, expressed as iron oxide by firing at 800 to 1600 ° C for 0.5 up to 12 hours with a continuous flow of nitriding and / or shielding gas to give a product which is adjusted by grinding to a fineness of particles in the range of 0.01 to 5 µm, characterized in that the powdered product in the form of a suspension in liquid is magnetically separated at 0.05 to 1 T and separating the non-magnetic low-iron fraction from the magnetic fraction of the synthesis product powder. 2. The method according to claim 1, characterized in that the removed magnetic portion of the powder is returned as an intensifying additive and by catalytic and nucleating effect to the raw material mixture. t.