Method and apparatus for radio frequency ceramic sintering
AssigneeMartin Marietta Energy Systems, Inc.
InventorsDaniel J. Hoffman, Harold D. Kimrey, Jr.
Life of this patent
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Abstract
Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents.
Claims18
An apparatus for sintering a ceramic material comprising:
- a radio frequency power supply having a frequency and impedance;
- waveguide means, coupled to the radio frequency power supply, for generating a high electric field capacitive region when powered by the radio frequency power supply;
- and
- means for forming a uniform electric field comprising loose dielectric material cooperating with said electric field generating means to provide a uniform, electric field capacitive region;
- means for holding a sample of the ceramic material in the high electric field capacitive region, whereby volumetric heating in the ceramic sample results when the radio frequency fields encounter the ceramic material's residual dielectric losses.
In combination, a system for sintering a ceramic material and a ceramic material to be sintered comprising:
- a high-loss, high-temperature ceramic material;
- a radio frequency power supply for volumetric heating of ceramic materials having a frequency impedance;
- waveguide means, coupled to the radio frequency power supply, for generating a high electric field capacitive region when powered by the radio frequency power supply;
- means for forming a uniform electric field comprising loose dielectric material cooperating with said electric field generating means to provide a uniform, electric field capacitive region;
- and
- means for holding said ceramic material in high electric field capacitive region, whereby volumetric heating in the ceramic sample results when the radio frequency field encounters the ceramic materials residual dielectric losses.
A method for sintering a ceramic material comprising:
- providing a radio frequency power supply having a frequency and impedance;
- generating a high electric field capacitive region when powered by the radio frequency power supply with waveguide means coupled to the radio frequency power supply;
- forming a uniform electric field by encasing the ceramic material in a loose dielectric material;
- and
- holding a sample of the ceramic material in the uniform high electric field capacitive region, whereby volumetric heating in the ceramic sample results when the radio frequency field encounter the ceramic material's residual dielectric losses.
A uniformly sintered ceramic material prepared by, providing a ceramic material to be sintered in a loose dielectric casket prepared by:
- providing a radio frequency power supply having a frequency and impedance;
- generating a uniform high electric field capacitive region by using the radio frequency power supply and waveguide coupled thereto in combination with the loose dielectric casket surrounding the ceramic material to be sintered;
- and
- holding a sample of the ceramic material to sintered in the uniform high electric field capacitive region, whereby volumetric heating in the ceramic sample results when the radio frequency field encounters the ceramic material residual dielectric losses.
Dependencies are inferred from the claim text.