Methods for producing solid, substantially round, spherical and sintered particles from a slurry of a raw material having an alumina content of greater than about 40 weight percent. The slurry is processed to prepare green pellets which are sintered in a furnace with microwave energy at a temperature of 1480 to 1520 C. to produce solid, substantially round, spherical and sintered particles having an average particle size greater than about 200 microns, a bulk density of greater than about 1.35 g/cm.sup.3, and an apparent specific gravity of greater than about 2.60.

Disclosed herein are apparatus and methods for densification of a green part composed of metal powders held by a binder under a controlled atmosphere with microwave energy. In particular embodiments, the microwave densification can occur in a continuous, uninterrupted sequence, including the steps of thermal debinding, sintering and infiltration with a secondary infiltrant metal powder. In specific embodiments, the secondary infiltrant metal powder has a lower melting temperature than the metal powders in the green part, and the powder size ratio between the metal powders in the green part and the secondary infiltrant metal powder is selected such that the heating rates of the powders under microwave energy are approximately equalized.

Carriers suitable for transporting a plurality of articles through a microwave heating zone are provided. Carriers as described herein may include an outer frame and upper and lower support structures vertically spaced from one another to provide a cargo volume into which the articles are loaded. At least a portion of the upper and/or lower support structures may be formed of an electrically conductive material. Additionally, the carrier may include removable article spacing members, such as vertical spacing members and dividers, that can be selectively inserted to adjust the size and/or shaper of the cargo volume. Carriers as described herein may be configured to receive a variety of different articles, including trays and pouches, and the articles may be loaded into the carrier in a nested or overlapping manner.

A household or commercial appliance includes a couple magnetrons having relative anodes and cathodes, and a power unit comprising a high voltage circuit. The high voltage circuit comprises: a high voltage transformer comprising a primary winding connected to an alternating voltage source and a secondary high-voltage winding providing an alternating high voltage having a period comprising two half periods, a couple of half-wave voltage doubler circuits, and first and second unidirectional conducting devices. The first and second unidirectional conducting devices being configured to cause the half-wave voltage doubler circuits to supply, during a period of the alternating high-voltage the doubled high-voltage to the cathode of the respective magnetron alternately.

A microwave oven and a method of operating the same is provided herein. The method includes the steps of: sensing that a door of the microwave is in an open state; interrupting a power input to a generator power supply unit comprising a first converter, a first energy reserve, a second energy reserve located downstream from the first energy reserve, and a second converter located between the first and second energy reserves; detecting an input voltage; and disabling the second converter if the detected input voltage is less than a threshold voltage that is proportional to the detected input voltage, wherein disabling the second converter triggers the second energy reserve to discharge, and wherein the time necessary to discharge the second energy reserve is free of influence from the first energy reserve and is independent of the detected input voltage.

Embodiments described herein provide a microwave coupler that utilizes a microwave shield within an interior of the microwave coupler to mitigate Radio Frequency (RF) leakage from an end of the microwave coupler. The microwave coupler includes a ramp section that is configured to mate to a microwave source, with the ramp section extending from an opening in a top wall of an enclosure. One end of the enclosure is configured to mate to a microwave waveguide, while an opposing end may be open or partially open. The microwave shield is located between the opposing end of the enclosure and the opening in the top wall, and extends from the top wall of the enclosure towards a bottom wall of the enclosure.

Systems and methods are provided for chokes for microwave radiation. One embodiment is an apparatus that includes a choke assembly. The assembly includes a first choke plate, and a second choke plate. The assembly also includes a first layer disposed at a surface of the first choke plate. The first layer includes a material that attenuates microwave radiation via dielectric heating by converting the microwave radiation into heat, and a substance, disposed between the material of the first layer and the gap, that is transparent to the microwave radiation. The assembly further includes a second layer disposed at a surface of the second choke plate that faces the first layer. The second layer comprises the material that attenuates the microwave radiation via dielectric heating by converting the microwave radiation into heat, and the substance, disposed between the material of the second layer and the gap.

Systems and methods are provided for chokes for microwave radiation. One embodiment is an apparatus that includes a choke assembly. The assembly includes a first choke plate, and a second choke plate. The assembly also includes a first layer disposed at a surface of the first choke plate. The first layer includes a material that attenuates microwave radiation via dielectric heating by converting the microwave radiation into heat, and a substance, disposed between the material of the first layer and the gap, that is transparent to the microwave radiation. The assembly further includes a second layer disposed at a surface of the second choke plate that faces the first layer. The second layer comprises the material that attenuates the microwave radiation via dielectric heating by converting the microwave radiation into heat, and the substance, disposed between the material of the second layer and the gap.

A volatile content analysis instrument is disclosed that includes a cavity and a microwave source positioned to produce and direct microwaves into the cavity at frequencies other than infrared frequencies. A balance is included with at least the balance pan (or platform) in the cavity. An infrared source is positioned to produce and direct infrared radiation into the cavity at frequencies other than the microwave frequencies produced by the microwave source. A lens is positioned between the infrared source and the balance pan for more efficiently directing infrared radiation to a sample on the balance pan. The lens has dimensions that preclude microwaves of the frequencies produced by the source and directed into the cavity from leaving the cavity.

A device and a method for heating and curing artificial stone with microwave are provided. The device includes a microwave curing cavity, within which an incompletely cured artificial stone is placed, and microwave is used to heat the artificial stone to completely cure the artificial stone; wherein, a frequency of the microwave is in a range of 3001120 MHz. The present disclosure provides a separately designed microwave curing cavity, and utilizes 3001120 MHz microwave having a large penetrating depth, to realize a rapid curing of a large-sized artificial stone.