FR2544305A1 - CONSTITUENT ELEMENTS OF SINTERED ALUMINUM NITRIDE TUBES FOR USE IN LASER TUBES - Google Patents

Abstract

MAXIMUM DENSITY SINTERED ALUMINUM NITRIDE HAS GOOD THERMAL CONDUCTIVITY, HIGH ELECTRICAL STRENGTH, GOOD DIELECTRIC PROPERTIES AS WELL AS HIGH MECHANICAL RESISTANCE AND IS THEREFORE A CONSTITUENT OF APPROPRIATE MATERIAL.

Description

The invention relates to components of tubes made of material

sintered ceramic

the maximum density.

  Owing to their good thermal conductivity and their high electrical resistance, sintered aluminum oxide is used for the constituent elements of the tubes and,

  in cases where the conditions no longer meet

  quises for ceramic-aluminum oxide, sintered beryllium oxide at maximum density (Ullmanns Encyklopddie der technischen Chemie, 4th edition, 1979,

volume 17, pages 525 to 527).

  Although beryllium oxide sintered at maximum density has very good properties, its high price and the toxicity of beryllium oxide dust prevent widespread use of this material. The object of the invention is therefore to find a ceramic material suitable for component parts of tubes which has properties as good as those of bdryllium oxide sintered at maximum density but which can

  be manufactured and implemented in a more economical way

  and without presenting a risk to health.

  This object is achieved according to the invention

  with aluminum nitride sintered at maximum density.

  The constituent elements of tubes made of aluminum nitride sintered at the maximum density according to the invention have a high mechanical resistance, a good resistance to thermal shocks, a high electrical resistance and good dielectric properties. beryllium oxide they keep their good thermal conductivity even at high temperatures, these components are particularly suitable for laser tubes The components of tubes according to the invention can be satisfactorily assembled with metals due to the coefficient of

  relatively high thermal expansion of aluminum nitride

  minimum sintered at maximum density. The starting material for the manufacture of the constituent elements of tubes preferably consists of powdery mixtures of aluminum nitride and of an addition of oxides representing a percentage by weight of 0.1 to 10%. These mixtures are used by cold compression to give green molded bodies which are sintered at maximum density in the atmosphere

  inert, preferably under nitrogen.

  The coefficient of thermal expansion and the thermal conductivity of sintered aluminum nitride can be influenced as desired at the maximum density by the nature and quantity of

addition of oxides.

  As oxides additions, the oxides of alkaline earth metals, rare earth metals (scandium, yttrium and lanthame up to lutenium), the oxides of the transition elements of group IV, V and VI of the periodic table of the elements, aluminum oxide and silicon oxide,

  either one or more of them.

  Yttrium oxide has given in particular

good results.

  Surprisingly moisture resistant, the highest density sintered aluminum nitride, which contains yttrium oxide. Other characteristics and advantages of the invention will be better understood on reading the

  description which follows of a manufacturing example

  of constituent elements of tubes according to the invention.

Example

  5000 g of a mixture composed of 99% by weight of powdered aluminum nitride and 1% by weight of powdered yttrium oxide are ground for 40 hours under argon as a protective gas in a ball mill with grinding elements ceramic, then put the mixture on a sieve with a mesh width

100 microns.

  With the powder obtained by sieving which has a grain size less than 100 microns, tubular molded parts are produced by cold isostatic compression (the pressure being 2500 bar) which are placed in an electric sintering oven After evacuation of air up to 10 5 mbar, nitrogen is blown into the sintering oven until the pressure reaches 5 mbar This pressure being maintained, the sintering oven is heated until it reaches

  within 3 hours a temperature of 1200 'C.

  Then the nitrogen pressure is increased to 140 mbar and

  the temperature increased within one hour to 1850 'C -

  the nitrogen pressure is then 180 mbar -.

We maintain this temperature and

  this pressure for 2 hours; then we cool.

  After aeration of the sintering furnace, the elements are removed

  made of tubes, sintered at maximum density.

  The elements of tubes manufactured in this way have a coefficient of 6 K-1 thermal expansion of 4 10 K, a thermal conductivity of 200 W / m K and a flexural strength of 320 N / mm

Claims (6)

  1 Components of tubes made of sintered ceramic material at maximum density, characterized in that they consist of aluminum nitride sintered at maximum density.   2 Components of tubes according to.   claim 1, characterized by one or more oxide (s) additions.   3 constituent elements of tubes according to claim 2, characterized in that the additions are oxides of alkaline earth metals, rare earth metals, oxides of the transition elements of group IV, V or VI of the periodic classification of segments , aluminum oxide or oxide of silicon.   4 constituent elements of tubes according to claim 2 or 3, characterized in that the content of additions represents a percentage by weight included between 0.1 and 10%.   5 Components of tubes according to   one of claims 2 X 4, characterized in that   the addition consists of yttrium oxide.   6 Elements constituting tubes according to   one of claims 1 to 5, characterized in that they   are components of laser tubes.