Method for preparing ceramic powders in the presence of a carbon source, powders obtained and use thereof

Abstract

The invention concerns a method for preparing ceramic powders in the presence of a carbon powder comprising a step which consists in homogenizing a mixture of particles capable of resulting in a ceramic by heat treatment. Said method can be carried out in the presence of an accelerated solvent and provides, at reduced energy consumption, carbon-coated ceramic powders and then ceramics.

1 . Process for the preparation of a ceramic powder from a mixture of precursors of said powder and in the presence of at least one source of carbon, comprising at least one of the following steps: 
 a) homogenization, in the presence of the source of carbon and eventually in the presence of a solvent, to obtain an intimate mixture of precursor particles that can result in a ceramic product by heat treatment;    b) removal of the solvent eventually present in the intimate mixture obtained in step a); and    c) carbonization of the residual carbon that is present in the intimate mixture of precursors obtained in step a) or b) when the source of carbon does not essentially consists of carbon, by heat treatment of said intimate mixture obtained in step a) or b).    
     
     
         2 . Process of preparation according to  claim 1 , in which the source of carbon is in liquid, solid, gaseous form or in heterogeneous form, said process being at least partially carried out in the presence of a solvent that facilitates homogenization of the mixture of precursors of said ceramic powder that are used at the start of said process.  
     
     
         3 . Process of preparation according to  claim 2 , in which the source of carbon in liquid form is selected from the group consisting of: 
 one or more hydrocarbons; or    one or more polymers having a molecular weight higher than 50,000.    
     
     
         4 . Process of preparation according to  claim 3 , in which the liquid source of carbon consists of a mixture of liquid hydrocarbons at room temperature.  
     
     
         5 . Process of preparation according to  claim 4 , in which the mixture of liquid hydrocarbons at room temperature consists of a refinery waste.  
     
     
         6 . Process of preparation according to  claim 5 , in which the refinery waste consists of a petroleum coke or a breakage coke.  
     
     
         7 . Process of preparation according to  claim 3 , in which the source of carbon in liquid form consists of a mixture of or based on oxygenated polymers.  
     
     
         8 . Process of preparation according to  claim 7 , in which the source of carbon in liquid form consists of a mixture of polymer oxide in acetonitrile.  
     
     
         9 . Process according to any one of  claim 1 , in which the source of carbon in solid form is selected from the group consisting of synthetic or natural carbon particles, or a mixture thereof.  
     
     
         10 . Process of preparation according to  claim 9 , in which the particles of carbon are Ketjen black particles, Shawinigan black particles, or a mixture thereof.  
     
     
         11 . Process of preparation according to  claim 9 , in which the source of solid carbon that is used has a purity higher than 50%.  
     
     
         12 . Process of preparation according to  claim 9 , in which the impurities that are present in the source of solid carbon are selected from the group consisting of sulfur, nitrogen and oxygen.  
     
     
         13 . Process according to  claim 1 , in which the source of carbon in gaseous form is selected from the group consisting of alkanes, alkenes, alkynes or a mixture thereof.  
     
     
         14 . Process of preparation according to  claim 13 , in which, the source of gaseous carbon is selected from the group consisting of CH 4 , C 2 H 6 , C 2 H 2  and a mixture thereof.  
     
     
         15 . Process of preparation according to  claim 1 , in which homogenization step a) is carried out by grinding.  
     
     
         16 . Process of preparation according to  claim 15 , in which the grinding is of the high energy type.  
     
     
         17 . Process of preparation according to any one of  claim 1 , in which the temperature during the removal step b) is between 40 and 150° C.  
     
     
         18 . Process according to  claim 17 , in which the temperature of removal of the solvent is between 60 and 120° C.  
     
     
         19 . Process of preparation according to  claim 3 , in which the source of carbon as well as the solvent are introduced during step a).  
     
     
         20 . Process of preparation according to  claim 1 , carried out at least partially under a reducing atmosphere, said reducing atmosphere preventing transformation of the carbon, that is present in the reaction mixture, into carbon dioxide, and allowing to obtain particles of ceramic powder that are coated with carbon.  
     
     
         21 . Process of preparation according to  claim 1 , in which the solid source of carbon consists of particles of carbon having a size that varies between 10 and 900 nanometers.  
     
     
         22 . Process of preparation according to  claim 21 , in which the particles of carbon used have a specific surface, measured according to the BET method, that is greater than 50 m 2 /g.  
     
     
         23 . Process of preparation according to  claim 1 , in which the mixture of particles that can result in a ceramic product by heat treatment, is a mixture of particles of ZrO 2  and particles of Y 2 O 3.    
     
     
         24 . Process of preparation according to  claim 1 , in which the mixture of particles that can result in a ceramic product by heat treatment is a mixture of particles of Li 2 TiO 3  and of particles of TiO 2 .  
     
     
         25 . Process of preparation according to  claim 1 , in which the mixture of particles that can result in a ceramic product by heat treatment is a mixture of particles of Li 2 TiO 3  and of particles of TiO 2  and in which the source of carbon is a polyoxyethylene based polymer.  
     
     
         26 . Process of preparation according to  claim 1 , in which the particles of the mixture that can result in a ceramic product have a size between  1  nanometer and 10 micrometers.  
     
     
         27 . Process of preparation according to  claim 23 , in which the particles of ZrO 2  or Y 2 O 3 , have a size that varies between 1 and 10 microns.  
     
     
         28 . Process of preparation according to  claim 2 , in which the solid source of carbon, that is a carbon powder, has a size distribution characterized by a D50 between 10 nanometers and 10 micrometers.  
     
     
         29 . Process of preparation according to  claim 2 , in which the source of carbon consists of a polymer or a hydrocarbon in powder form in which the particles have a D50 of 10 nanometers to 500 nanometers.  
     
     
         30 . Process of preparation according to  claim 1 , in which the source that can result in a ceramic product by heat treatment has a size distribution characterized by a D50 between 10 nanometers and 10 micrometers.  
     
     
         31 . Process of preparation according to  claim 1 , in which the particles used have size dimensions close to 1 micrometer.  
     
     
         32 . Process of preparation according to  claim 1 , in which the homogenization is carried out in step a) of the process, under dry conditions and/or with or in a solvent.  
     
     
         33 . Process of preparation according to  claim 1 , in which step a) lasts between 1 and 3 hours.  
     
     
         34 . Process of preparation according to claims  33 , in which step a) lasts about 2 hours.  
     
     
         35 . Process of preparation according to  claim 5 , in which step c) lasts 3 to 24 hours.  
     
     
         36 . Process of preparation according to  claim 35 , in which step c) lasts about 3 hours.  
     
     
         37 . Process of preparation according to  claim 1 , in which at least one of the steps is carried out under inert atmosphere.  
     
     
         38 . Process according to  claim 1 , in which at least one step of the process is carried out in the presence of a source of oxygen, in order to remove any trace of residual carbon from the ceramic powder obtained at the end of the process.  
     
     
         39 . Process according to  claim 15 , in which the source of carbon is at least in part in liquid and/or gaseous form.  
     
     
         40 . Process according to  claim 38 , in which step a) of solvent removal is carried out at a temperature between 200 and 500 degrees Celsius and for a duration of heat treatment between 12 and 24 hours.  
     
     
         41 . Process according to  claim 39 , in which the step of carbonization is carried out in the reactor that was used for homogenizing the mixture that can result in a ceramic product by heat treatment.  
     
     
         42 . Process of preparation according to  claim 1 , in which the particles of the ceramic powder obtained have a particle size between 10 nm and 1 micron.  
     
     
         43 . Process of preparation according to  claim 41 , in which the particle size dimension of the ceramic powder obtained is between 50 and 500 nm.  
     
     
         44 . Process of preparation according to  claim 1 , in which the temperature, in homogenization step a), varies from 20 to 40° Celsius.  
     
     
         45 . Process of preparation according to  claim 44 , in which the temperature in step a) is about 25° C.  
     
     
         46 . Process of preparation according to  claim 1 , in which the temperature in carbonization step c) is between 200 and 450° Celsius.  
     
     
         47 . Process of preparation according to  claim 46 , in which the temperature in step c) is about 400° C.  
     
     
         48 . Process of preparation according to  claim 1 , in which the quantity of carbon source used in said process represents 2 to 10 weight percent of the particles that can result in a ceramic product by heat treatment.  
     
     
         49 . Process of preparation according  claim 1 , in which the source of carbon is a polymer and the quantity of polymer used in said process represents from 5 to 30 weight percent of the mixture of particles that can result in a ceramic powder by heat treatment.  
     
     
         50 . Process of preparation according to  claim 23 , in which the quantity of Y 2 O 3  in the mixture of particles subject to grinding varies between 5 and 15 weight percent and the quantity of ZrO 2  varies between 5 and 15 weight percent.  
     
     
         51 . Process of preparation according to  claim 1 , in which the ceramic powder obtained in step b) or in step c) is of the nano type.  
     
     
         52 . Process of preparation according to  claim 50 , in which the particle size of the ceramic particles obtained is between 10 and 900 nanometers.  
     
     
         53 . Ceramic powder obtained by one of the process defined in  claim 1 .  
     
     
         54 . Ceramic powder according to  claim 53 , consisting of particles of LiTi 2 O 4  coated with carbon.  
     
     
         55 . Ceramic powders obtained by carrying out the process defined in  claim 20 .  
     
     
         56 . Process for preparing a ceramic product incorporating the steps defined in  claim 1  and a step in which the ceramic powder obtained is subjected to at least one heat treatment at a temperature higher than 800° Celsius.  
     
     
         57 . Ceramic product obtained by the process according to  claim 56 .  
     
     
         58 . Use of a ceramic powder according to  claim 53  in the field of fuel batteries or in the field of automobile.  
     
     
         59 . Use according to  claim 58  for the preparation of piston heads.  
     
     
         60 . Use according to  claim 58  for the preparation of ceramic anodes or ceramic electrolytes.  
     
     
         61 . Use of a ceramic powder as obtained by carrying out the process of  claim 37  in the manufacture of electrical ceramic insulators.  
     
     
         62 . Process of preparation according to  claim 23 , in which the mixture of particles of ZrO 2  and particles of Y 2 O 3  is a mixture consisting of x weight percent of particles of ZrO 2  and (100−x) weight percent of particles of Y 2 O 3 , where x varies from 1 to 99.  
     
     
         63 . Process of preparation according to  claim 62 , in which x is close to 50.  
     
     
         64 . Process of preparation according to  claim 24 , in which the mixture is a mixture consisting of x weight percent of particles of Li 2 TiO 3  and (100−x) weight percent of particles of TiO 2 , where x varies from 1 to 99.  
     
     
         65 . Process of preparation according to  claim 64 , in which x is close to 50.  
     
     
         66 . Process of preparation according to  claim 25 , in which the mixture is a mixture consisting of x weight percent of particles of Li 2 TiO 3  and (100−x) weight percent of particles of TiO 2 , where x varies from 1 to 99.  
     
     
         67 . Process of preparation according to  claim 66 , in which x is close to 50.  
     
     
         68 . Process of preparation according to  claim 25 , in which the source of carbon is a polyoxyethylene based polymer having an average molecular weight of 54000.  
     
     
         69 . Process of preparation according to  claim 25 , in which said polyoxyethylene based polymer is dissolved before carrying out the homogenization step in an aqueous or organic solvent.  
     
     
         70 . Process of preparation according to  claim 69 , in which the organic solvent is acetonitrile.  
     
     
         71 . Process of preparation according to  claim 26 , in which the particles have a size between 20 and 800 nanometers.  
     
     
         72 . Process of preparation according to  claim 24 , in which the particles of TiO 2  or Li 2 TiO 3  have a size that varies between 1 and 10 microns.  
     
     
         73 . Process of preparation according to  claim 25 , in which the particles of TiO 2  or Li 2 TiO 3  have a size that varies between 1 and 10 microns  
     
     
         74 . Process of preparation according to  claim 28 , in which the size distribution is characterized by a D50 between 100 nanometers and 2 micrometers.  
     
     
         75 . Process of preparation according to  claim 29 , in which the particles have a D50 of 10 to 200 nanometers.  
     
     
         76 . Process of preparation according to  claim 30 , in which the size distribution is characterized by a D50 between 100 nanometers and 2 micrometers.  
     
     
         77 . Process of preparation according to  claim 31 , in which the particles used have size dimensions characterized by D50 lower than or equal to 1 micrometer.  
     
     
         78 . Process of preparation according to  claim 32 , in which the homogenization is carried out in step a) of the process under dry conditions by means of an Aglomaster mixer of HOSOKAWA, Japan.  
     
     
         79 . Process of preparation according to  claim 32 , in which the homogenization is carried out in step a) with or in a solvent by means of a mechano-fusion device of HOSOKAWA, Japan.  
     
     
         80 . Process of preparation according to  claim 37 , in which the inert atmosphere is a nitrogen atmosphere, an argon atmosphere or a nitrogen-argon atmosphere.  
     
     
         81 . Process of preparation according to  claim 40 , in which the temperature is of about 400° C. and the duration is of about 20 hours.  
     
     
         82 . Process of preparation according to  claim 48 , in which the quantity of carbon source used in said process represents about 6 weight percent of the particles that can result in a ceramic product by heat treatment.  
     
     
         83 . Process of preparation according to  claim 49 , in which the quantity of polymer used in said process represents about 20 weight percent of the mixture of particles that can result in a ceramic powder by heat treatment.  
     
     
         84 . Process of preparation according to  claim 49 , in which the quantity of polymer used in said process represents from 5 to 30 weight percent of the mixture of particles that can result in a ceramic powder by heat treatment.  
     
     
         85 . Ceramic powders obtained by carrying out the process defined in  claim 23 .  
     
     
         86 . Use of a ceramic powder according to  claim 54 , in the field of fuel batteries or in the field of automobile.  
     
     
         87 . Use of a ceramic powder according to  claim 55 , in the field of fuel batteries or in the field of automobile.  
     
     
         88 . Use of a ceramic product according to  claim 57 , in the field of fuel batteries or in the field of automobile.