Analytical process in which materials to be analyzed are directly and indirectly heated and dried by microwave radiation
First Claim
1. A process for/analyzing a thermally sensitive material for its content of volatilizable components without degrading the material, which comprises supporting the material to be analyzed, which includes lossy and non-lossy volatilizable component(s), by means of a support which comprises 40 to 95% of a matrix material which is transmissive of microwave radiation, 5% to 60% of a microwave absorptive material dispersed in such matrix material, which microwave absorptive material has a Curie temperature in the range of 85°
- to 650°
C., above which it becomes microwave transmissive, so as thereby to prevent excessive heating of the support and the material to be analyzed, which matrix material is stable and form retaining at the Curie temparature of the dispersed material, and directing microwave radiation onto the material to be analyzed and onto the support for such material so as directly to heat the material when it contains lossy volatilizable component(s) and indirectly to heat such material by heating the support when the material to be analyzed no longer contains any lossy component(s), which support heats the material to a temperature no higher than the Curie temperature of the dispersed microwave absorptive material in the matrix of the support, at which temperature the material being analyzed is not degraded, and applying sufficient microwave radiation to bring the microwave absorptive material of the support to its Curie temperature.
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Abstract
An apparatus for controllably heating material, such as a material to be analyzed for volatiles or non-volatiles contents, directly and indirectly by microwave radiation, includes a chamber, in which the material to be heated is placed, a source of microwave radiation, for radiating onto materials in the chamber and for controllably heating such a material, and a support for such material, which support includes a matrix of a material which transmits microwave radiation, and also includes particulate material therein which absorbs microwave radiation. The absorptive material is one that has a Curie temperature, above which it is transmissive of microwave radiation, so as thereby to prevent excessive heating of the support and the supported material which is to be heated. The matrix material is stable and form-retaining at the Curie temperature of the dispersed material. Preferably the support matrix will be of a silicone rubber or of a polyfluoroalkylene polymer, such as polytetrafluoroethylene, and the dispersed material will be a ferrite, garnet or a mixture thereof. The apparatus may include a turntable for one or more supports, an automatic electronic balance, computerized controls and readout means. Also within the invention are the described support, and processes for heating and drying, in a preferred embodiment of which processes a particulate diluent or dispersant for the sample being treated is employed to prevent overheating of the sample.
66 Citations
10 Claims
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1. A process for/analyzing a thermally sensitive material for its content of volatilizable components without degrading the material, which comprises supporting the material to be analyzed, which includes lossy and non-lossy volatilizable component(s), by means of a support which comprises 40 to 95% of a matrix material which is transmissive of microwave radiation, 5% to 60% of a microwave absorptive material dispersed in such matrix material, which microwave absorptive material has a Curie temperature in the range of 85°
- to 650°
C., above which it becomes microwave transmissive, so as thereby to prevent excessive heating of the support and the material to be analyzed, which matrix material is stable and form retaining at the Curie temparature of the dispersed material, and directing microwave radiation onto the material to be analyzed and onto the support for such material so as directly to heat the material when it contains lossy volatilizable component(s) and indirectly to heat such material by heating the support when the material to be analyzed no longer contains any lossy component(s), which support heats the material to a temperature no higher than the Curie temperature of the dispersed microwave absorptive material in the matrix of the support, at which temperature the material being analyzed is not degraded, and applying sufficient microwave radiation to bring the microwave absorptive material of the support to its Curie temperature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- to 650°
Specification