| 摘要 |
Binary crystalline compounds are produced by preparing a mixture consisting essentially of the two constituent elements of the compound and a third element which has a melting point within the range of temperatures in which the said compound can exist in the desired crystalline form, and in which third element at least one of the constituent elements of said compound is soluble when the third element is molten; heating the mixture and agitating it so as to produce a mixture consisting essentially of a liquid phase and two solid phases, the liquid phase being a saturated solution of at least one of said constituent elements in the third element and the two constituent elements being present respectively in the two solid phases; continuously agitating the mixture so produced while maintaining it at a temperature, within the range of temperatures in which the said compound can exist in the desired crystalline form, such that the compound is formed in said crystalline form by reaction between a solute element and the solid phase in which the other constituent element is present and such that the compound is stable with respect to the third element; and separating the compound from the remainder of the mixture produced by the first three steps. The elements in the initial mixture may be present at least partially in combined or alloyed form. In the example the b polymorph of thorium disilicide is formed by placing a mixture of silicon, bismuth and thorium in a silica capsule which is pressurized, sealed and subjected to vibration. After heating the capsule to above 271 DEG C. (m.p. of Bi) and then to 700 DEG C., the product of thorium disilicide embedded in a solid matrix of bismuth, thorium and silicon is treated with nitric acid and the crystals of thorium disilicide separated from the remaining thoria and silicon by screening. Thorium digermanide and uranium disilicide may be prepared in a similar way. Reference has been directed by the Comptroller to Specification 889,775. |
