CZ110193A3 - Process for producing ceramic membrane - Google Patents

Abstract

This method of producing porous ceramic membranes by plasmatic coating where the ceramic powder is applied to the plate by a water stabilised plasmatron at a deposition distance of 200 to 400 mm. at a voltage of 310 to 320 V and a discharging current of 480 to 500 A from which, after the creation of the layer, the ceramic membrane is separated.

Description

Technical field what about it

The invention relates to a process for the production of ceramic membranes suitable for separation purposes, particularly in the chemical and food industries.

\

BACKGROUND OF THE INVENTION.

The prior art ceramic membranes are made of powdered ceramic material, for example Al2O3, ZrSiO4 and the like, which is molded at a pressure of about 200 MPa and subsequently sintered at temperatures of 1300 to 1450 θ (3.

The drawbacks of the production process described above are that the membranes thus produced exhibit a wide pore size distribution, high production costs and long production times. Also, because of the relatively low attainable temperatures, it is not possible to process very high melting points in this production process.

SUMMARY OF THE INVENTION

The aforementioned drawbacks are overcome by the method of manufacturing a ceramic membrane, which consists in that the ceramic powder is applied with a water-stabilized plasmatron at a deposition distance of 200 to 400 mm, a voltage of 310 to 320 V and a discharge current of 480 to 500 A is applied to the substrate from which the ceramic membrane is separated after the layer has been formed.

The advantages of these membranes reside in their high thermal and chemical stability, i.e., they are also applicable at temperatures above 1000 ° C and in plants using acids or alkalis.

Examples

Example 1

Powdered aluminum oxide with a granulometry of 80 - 100 gm, was plasma sprayed onto a steel substrate up to a thickness of 1 mm. The operating mode of the water stabilized plasma torch was 310 V and 480 A. The flow rate of the stabilizing medium, in this case water, was 0.2 l / min. and a carrier gas overpressure of 150 kPa. The prepared sample was then treated with 20% hydrochloric acid for three hours, after which time the ceramic membrane was easily separated.

Example 2

ZrSiO4 powder with a particle size of 40-80 gm was sprayed onto the molybdenum substrate to a thickness of 0.8 mm. The operating mode of the plasma torch was the same as in Example 1 except that the powder feeder was located closer to the center of the plasma cone. The membrane from the substrate was separated by short-term, i.e. 2-minute oxidation of the molybdenum substrate at 970 ° C.

116 gm was 0.5 mm in plasma. Discharge After plasma spraying was

Example 3

The SiC o. Granulometry was sprayed onto the molybdenum substrate to a current of 500 A, a voltage of 320 V was formed and subjected to a hot isostatic pressing process (HIP) in an argon atmosphere in the presence of saturated hydrocarbons C _n H 2 _n / Ar at 1750 ° C and pressure 150 MPa. The silicon coating was converted to β - SiO to form a membrane from a compound that otherwise cannot be sintered separately. The separation was carried out as described in Example 2.

Example 4

Titanium Ti powder with a granulometry of 50-100 gm < -1 > was plasma sprayed onto a carbon substrate to a thickness of 1 mm. The plasma mode was the same as in Example 1, except that the deposition distance was less, i.e. 300 mm. As a result of the reaction of titanium,

air was formed on the graphite base coating of cermet Ti-Ti-TiO2. No special procedure was necessary to separate the membrane from the carbon substrate due to the low adhesion of the two materials.

Example 5

Powdered mullite 2S1O2. 3AI2O3 with a granulometry of 40 - 65 µm was plasma sprayed onto a steel support up to a thickness of 1 mm. The plasma process parameters were the same as in Example 4. The resulting membrane was separated from the steel substrate by thermal shock, i.e. immediately after spraying, by embedding the substrate with the membrane with cold water.

In principle, any ceramic material may be used for the plasma spraying of ceramic membranes described above. In this technology it is also possible to use materials with a very high melting point, for example titanium diboride TiB2, the melting point of which is 2980 ° C.

Industrial applicability

Ceramic membranes made by the above-described method can be used for separation purposes, for example for filtration or microfiltration, for surface treatment, for water purification, in the food industry for beverage purification, for milk separation, for gas separation in bio-reactors, especially chemically strongly aggressive environments.

Claims (6)

PATENT CLAIMS b \ 't A process for the production of ceramic membranes, characterized in that the ceramic powder is applied to a plasma stabilizer at a deposition distance of 200 to 400 mm, a voltage of 310 to 320 V and a discharge current of 480 to 500 A a substrate from which the ceramic membrane is separated after the layer has been formed. 2. The process for producing ceramic membranes according to claim 1, characterized in that the ceramic powder is Si. 3. The process for producing ceramic membranes according to claim 2, characterized in that after the plasma deposition, the substrate-bonded silicon membrane is subjected to hot isostatic pressing in an atmosphere of C _n H2 _n / Ar at a temperature between 1500 and 1800 ° C and pressure. in the range from 100 to 150 MPa. 4. The process for producing ceramic membranes according to claim 1, characterized in that the separation of the membrane from the substrate is carried out by etching with hydrochloric acid for a period of from 1 to 6 hours. 5. The process for producing ceramic membranes according to claim 1, characterized in that the separation of the membrane from the substrate is carried out by oxidation for 1 to 10 minutes at a temperature of at least 970 ° C. 6. The process for producing ceramic membranes according to claim 1, characterized in that the membrane is separated from the substrate by quenching.