DE2408874A1 - Chemical conversion of compact metals into fine particles - by treatment in molten chlorides contg a conversion-active salt - Google Patents

Abstract

In the chemical conversion of compact metals into particles with a large surface area, the compact metal is (partially) enveloped by a molten salt, contg. 0.01 wt.% of a conversion-active salt, for an adequate period of time and the resulting needle- and/or dendritic- shaped crystals, or fine crystalline powder, removed from the melt or the latter allowed to solidify and dissolved out. The compact metals may be wire, turnings, granules and/or metal scrap, and the molten salts alkali(ne earth) halides, or the alkali-or ammonium-salts of organic acids with high m.pt. The conversion-active salts are pref. halides of the transition metals. The process is useful for obtaining a large surface area, e.g. for catalysts or surface roughening, or localised, selective roughening using a laser beam to melt a thin layer of salt on a substrate for data storage.

Description

Process for chemical forming of metallic materials.

In technology, metallic substances are used for numerous applications required in finely divided form. Examples are catalysts, catalyst carriers and called heat exchanger masses.

Metals and alloys in finely divided form are used for this. It is also used for surface treatment by enamelling, coloring, etc. or Surface finishing is often a targeted roughening of the metal surfaces to be treated significant.

The invention described below enables both reshaping of compact metallic bodies as well as the targeted roughening of metal surfaces. The process is characterized in that the compact metallic substances be completely or partially surrounded by a molten salt which is at least 0.01 % By weight of forming salts, the melt acts for a sufficient period of time and the needle-shaped and / or dendrite-shaped crystals or finely crystalline ones formed Powder removed from the melt or exposed by dissolving the solidified salts will.

The procedure is explained in more detail below using examples will.

Example 1: Production of finely divided copper masses.

In a eutectically composed melt of 10 kg of sodium and potassium chloride, which contains approx. 0.9% by weight nickel chloride (NiCl2) as effective for forming Contains halide, dissolved. will be approx.

2 kg of copper scrap, granules and remnants of copper cathodes slowly entered the copper refining process. The 3-10 mm large copper pieces (starting body ) are located on ceramic hordes and are fully covered by the melt. After about 20 hours, the compact starting bodies have turned into a voluminous mass Reshaped copper dendrites. She is slowly lifted from the melt with the ilorden, cooled and finally exposed by dissolving away the remaining solid salts. The relative surface enlargement is around 1: 104. The dendrites and copper needles have a thickness of 1-50 / µm and a length of up to # 1 cm. It is noticeable that the surface of the dendrites partially show a microscopic roughening. That Nickel introduced as NiC12 is almost completely in the copper dendrites. By adding forming-effective NiCl2 to the melt, the forming process can take several steps To be repeated times.

In this way, depending on the specified NiCl2 content of the melt, it is possible Different compositions of copper-nickel alloys with a large surface to manufacture. Should the nickel concentration in the formed copper be relatively high (2 wt.% B so discontinuously or continuously a Mixture of nickel chloride, sodium and potassium chloride while stirring the melt added.

The procedure is not limited to the above-mentioned exit keys.

The continuous and partial roughening of metal wires, Ribbons, etc. made of pure metals or alloys is possible in a simple manner. For this purpose, the above-mentioned bodies are slowly moved by the melt, which has a correspondingly effective forming effect Sal7 contains, pulled through.

It was found that with increasing temperature and decreasing content the relative surface enlargement of the active halides decreases. The rate of shaping increases with increasing temperature and concentration of forming salts in the melt. During the forming process takes place at the same time cleaning takes place. In this way, heterogeneous proportions in the starting bodies, such as oxides, Carbides, borides, etc., separated or

not built into the formed body. They prefer to gather at the bottom of the conversion vessel.

The method is capable of a variety of changes. As a molten salt In addition to alkali halides, the halides of the alkaline earths or alkali and / or ammonium salts of high-melting organic acids, such as aliphatic carboxylic acids with more than four carbon atoms per molecule, phthalic acids, salicylic acid, etc. Above all, the salts of the organic acids enable reshaping or roughening the compact starting body at temperatures in the range from 1000 to 4000C.

The halides are particularly suitable as salts that are effective for forming of transition metals (T-metals). Furthermore, it is # o possible the most effective for forming Generate salts in situ in the melt.

For this purpose, it is sufficient to reform with a low concentration of active reforming agents Start salting, with the melt at the same time being the metal of the deformable Contains salt in elemental form, but does not affect the original body. Further it is advantageous to use the forming salts by introducingTTalogens such as Chlorine and / or hydrogen halides such as chlorine hydrogen in the molten salt, which contains the corresponding metal in elemental form.

Example 2: The production of the forming salt.

The procedure is as in Example 1. Immerse in the molten salt however, nickel rods that do not come into direct contact with the copper starting bodies to have. The nickel concentration in the dendrites increases during the forming process to approx. 5 Gew.ff. Rapid transformation is achieved when the molten salt is largely or consists only of forming salts.

Example 3: High concentration of forming salts.

The procedure is as in Example 1. However, the molten salt persists from a mixture of copper-I-chloride (GuCi) and 25 Ges nickel bromide (NiBr2).

The reshaping is already completed after 5 hours and results a surface fermentation of approx. 1: 106.

The process is also suitable for targeted and partial roughening of metallic objects, such as sheet metal, strips, wires, etc .. This will be the initial body sprayed in a thin layer with the melt or the sufficient hot starting body dusted with a mixture of the appropriate salts, wherein melt the salts. If a liquid salt film created in this way is allowed to act, so the surface of the starting body becomes more or more depending on the time and temperature little roughened. Under roughening is a uniform roughness in the range of # 100 µm to understand. After treatment, the salts are removed by dissolving them or otherwise removed in a known manner from the starting bodies.

Example 4: The roughening of steel sheets.

A steel band (0.7 x 100 mm) with a low carbon content becomes horizontal at a speed of approx. 200 m / h through an approx. 0.5 long flame zone and so heated to approx. 700 ° C.

At the end of the flame zone, the top of the sheet is marked with a eutectic Mixture of sodium u. Potassium chloride with about 0.1% by weight nickel chloride (NiCl2) and approx. 0.1% by weight iron (II) chloride (PeCl2) dusted. The salts melt immediately and form an approx.

0.01 mm thick melt film, which is outside the flame zone by a Air shower is made to freeze. Melting of the salts and solidification of the Melt takes place in approx. 2 sec., The salt melt is then mixed with a CO2 -Laser beam melted in a punctiform manner, with a roughness of approx. 8 µm will. The sheet finally passes a washing zone in which the salts are removed. After thorough drying in a hot air zone of 8000, the sheet steel rolled up.

The process is not limited to elemental metals. Even homogeneous or heterogeneous alloys can be reshaped or deliberately roughened. the The following table is intended to provide an insight into the possible variations. Included It must be taken into account that for the choice of the active salt, or preferred Salts of a foreign halide and not a halide of the metal to be transformed is used.

Table of formable metals and alloys.

Serial Metal or forming temperature no. Alloy effective det Molten salt salts 1 Cu NiCl2, FeCl2 700 ° C 2 Cu-Ni-Leg. CuCl 6000C 3 Cu-Ni-Si CuCl, FeCl2 700 ° C -Leg.

4 Ni-Si alloy. CuCl, FeCl2 700 ° C 5 Ni-Fe-Alloy. NiCl2, CuC1 FeCl2 6 Fe-Ti-Leg. FeCl2, TiCl- 800 ° C subchloride and TiCl4 7 Cr-Ni CrCl3, NiCl2 8000C FeCl2 8 Al-Ni AlCl3, NiCl2 800 ° C Except for the metallic substances mentioned in the table above further metals and alloys of transition metals including heavy metals transformable.

Claims (1)

Expectations 1) Process for the chemical reshaping of compact metallic materials in surface-rich body, characterized d the compact metallic Substances are completely or partially enveloped by a molten salt, which at least Contains 0.01% by weight of effective forming salts, the melt for a sufficient period of time acts and the needle-shaped and / or dendrite-shaped crystals or finely crystalline crystals formed Powder removed from the melt or exposed by dissolving the solidified salts will. 2-) Method according to claim 1) dgk., Dap as a metal to be formed Fabrics, wires, chips, granules and / or scrap metal are used in the process according to claim 1) and 2) dgk., dap the molten salt of alkali and / or alkaline earth halides or alkali and / or ammonium salts of high-melting organic acids. 4) Method according to claims 1) to 3) dgk. That as forming effective Salts halides of the transition metals are used. 5) Method according to claim 1 to 4 dgk. That the forming effective Halides in the molten salt in situ from halogens and / or hydrogen halides and elemental metal. 6) Method according to claim 1 dgk., Dap the molten salt for the most part Part consists of forming halides. 7) Method according to claim 1) to 6) dgk .. that for the purpose of alloy formation different types of metals are introduced into the molten salt, the different types However, metals do not touch each other. 8) Method according to claim 1) dgk. That the molten salt ze to cie materials to be reshaped or to be curled up in a thin layer by spraying on the Melt or brief immersion in the molten salt or by dusting the A sufficiently hot body with solid salts is applied. 9) Method according to claim 1) and 8) dgk. That the thin solidified Molten salt for the purpose of targeted roughening or information storage partially is melted by means of laser or other known light sources.