Patent Number: 
Section: claims

1. Neutron adsorbent material, characterized in that said material is a composite material comprising hafnium diboride and hafnium dioxide, in which the hafnium diboride represents at least 80% by volume of the material. 2. Material according to  claim 1 , in which the hafnium diboride represents about 90% by volume of the material. claim 1 3. Neutron adsorbent material, characterized in that said material is a composite material consisting of at least 80% by volume hafnium diboride and up to 20% by volume hafnium dioxide. 4. Material according to  claim 1 , in which the hafnium dioxide represents up to 20% by volume of the material. claim 1 5. Neutron adsorbent material, characterized in that said material is a composite material comprising hafnium diboride and hafnium dioxide, in which the hafnium dioxide represents about 10% by volume of the material. 6. Material according to  claim 1 , in which the hafnium dioxide represents about 10% by volume of the material. claim 1 7. Material according to  claim 2 , in which the hafnium dioxide represents about 10% by volume of the material. claim 2 8. Method of manufacturing a neutron absorbent material, said neutron absorbent material being a composite material hafnium diboride, said method comprising steps that consist of, in this order: adding hafnium dioxide powder to hafnium diboride powder,  mixing the hafnium diboride powder and the hafnium dioxide powder in a way that produces a homogeneous mixture, wherein when up to 20% by volume of hafnium dioxide is added, the homogeneous mixture of the hafnium diboride and hafnium dioxide represent 100% by volume and  sintering the homogeneous mixture in a way that produces the composite material. 9. Method according to  claim 8 , in which, about 10% by volume of hafnium dioxide is added, the homogeneous mixture of the hafnium diboride and hafnium dioxide representing 100% by volume. claim 8 10. Method according to  claim 8 , in which the hafnium diboride powder has a particle size ranging up to about 50 xcexcm. claim 8 11. Method according to  claim 9 , in which the hafnium diboride powder has a particle size ranging up to about 50 xcexcm. claim 9 12. Method according to  claim 10 , in which the hafnium diboride powder has a particle size ranging up to about 20 xcexcm. claim 10 13. Method according to  claim 11 , in which the hafnium diboride powder has a particle size ranging up to about 20 xcexcm. claim 11 14. Method according to  claim 10 , in which the hafnium diboride powder has a particle size ranging up to about 10 xcexcm. claim 10 15. Method according to  claim 11 , in which the hafnium diboride powder has a particle size ranging up to about 10 xcexcm. claim 11 16. Method according to  claim 8 , in which the mixture of the hafnium diboride powder and hafnium dioxide powder is produced by the application of ultrasound to a slip comprising said powders dispersed in a dispersion liquid. claim 8 17. Method according to  claim 8 , in which the homogeneous mixture is sintered under vacuum. claim 8 18. Method according to  claim 8 , in which the homogeneous mixture is sintered in a graphite mold lined with a sheet of graphite. claim 8 19. Method according to  claim 17 , in which the homogeneous mixture is sintered in a graphite mold lined with a sheet of graphite. claim 17 20. Method according to  claim 8 , in which the mixture is sintered at a temperature of from about 1600 to 2100xc2x0 C., under a pressure of from 15 to 100 MPa for a period of about 15 to 90 minutes. claim 8 21. Method according to  claim 8 , in which the mixture is sintered at a temperature of about 1900xc2x0 C., under a pressure of about 83 MPa for a period of about 1 hour. claim 8 22. Method according to  claim 8 , comprising additionally a step of machining the composite material over a thickness of about 500 to 1000 xcexcm. claim 8 23. Material according to  claim 7 , in which the hafhium dioxide is in the form of particles having a diameter ranging up to about 50 xcexcm. claim 7 24. Material according to  claim 7 , in which the hafnium dioxide is in the form of particles having a diameter ranging up to about 20 xcexcm. claim 7 25. Material according to  claim 7 , in which the hafnium dioxide is in the form of particles having a diameter ranging up to about 10 xcexcm. claim 7 26. Method according to  claim 17 , in which the mixture is sintered at a temperature of from about 1600 to 2100xc2x0 C., under a pressure of from 15 to 100 MPa for a period of about 15 to 90 minutes. claim 17 27. Method according to  claim 17 , in which the mixture is sintered at a temperature of about 1900xc2x0 C., under a pressure of about 83 MPa for a period of about 1 hour. claim 17 28. Material according to  claim 3 , in which the hafnium dioxide represents about 10% by volume of the material. claim 3 29. Material according to  claim 1 , in which the hafnium dioxide is in the form of particles having a diameter ranging up to about 50 xcexcm. claim 1 30. Material according to  claim 29 , in which the hafnium dioxide is in the form of particles having a diameter ranging up to about 20 xcexcm. claim 29 31. Material according to  claim 29 , in which the hafnium dioxide is in the form of particles having a diameter ranging up to about 10 xcexcm. claim 29 32. Material according to  claim 3 , in which the hafnium dioxide is in the form of particles having a diameter ranging up to about 50 xcexcm. claim 3 33. Material according to  claim 32 , in which the hafnium dioxide is in the form of particles having a diameter ranging up to about 20 xcexcm. claim 32 34. Material according to  claim 32 , in which the hafnium dioxide is in the form of particles having a diameter ranging up to about 10 xcexcm. claim 32 35. Material according to  claim 1 , having a density of about 10000 to11000 kg/m 3 . claim 1 36. Material according to  claim 35 , having a density of about 10550 to10630 kg/m 3 . claim 35