Hot surface igniters and methods of making same
AssigneeSpecialized Component Parts Limited, Inc.
InventorsCraig Andrew Willkens, Frederick Taylor Fernandez
Life of this patent
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Abstract
A method of making a hot surface igniter is described. A silicon carbide composition that includes both fines fraction and a coarse fraction is sintered in a nitrogen and argon reducing atmosphere in a manner that controls the incorporation of nitrogen with in the lattice of recrystallized silicon carbide. The controlled incorporation of nitrogen in the lattice provides enhanced control over heating and electrical properties, while simultaneously achieving a lower surface area fully recrystallized structure for oxidation resistance and long service life.
Claims60
A method of making a sintered hot surface igniter body, comprising:
- providing an unsintered, hot surface igniter body comprising silicon carbide, wherein the unsintered hot surface igniter body has a green density of greater than about 70 percent of a theoretical maximum density;
- sintering the unsintered hot surface igniter in a reducing atmosphere comprising nitrogen in an amount ranging from about 20 mole percent to about 80 mole percent of the reducing atmosphere to yield a sintered hot surface igniter body, wherein the sintered hot surface igniter body has a post sintering density that differs from the green density by no more than about five (5) percent.
A method of making a sintered hot surface igniter body, comprising:
- providing an unsintered hot surface igniter body comprising silicon carbide, wherein the silicon carbide comprises a fines portion and a coarse portion, and the coarse portion comprises at least about 20 percent by weight of the silicon carbide in the unsintered hot surface igniter body;
- sintering the unsintered hot surface igniter body in a partially-nitrogenated reducing atmosphere at one or more sintering temperatures ranging from about 2075° C. to about 2425° C. for a sintering period of from about 20 minutes to about 150 minutes.
A hot surface igniter having a hot surface igniter body, the hot surface igniter body comprising:
- a sintered silicon carbide composition having a high temperature resistivity at 1000° C. of from about 0.8 ohm-cm to about 3.5 ohm-cm.
A method of making a sintered hot surface igniter body, comprising:
- providing an unsintered hot surface igniter body comprising a proximal region adjacent a distal region along a length axis, wherein the proximal region and the distal region comprise silicon carbide;
- sintering the unsintered hot surface igniter body to yield a sintered hot surface igniter body, wherein the sintering step comprises:
- sintering the unsintered hot surface igniter body in a first reducing atmosphere at a first sintering temperature for a first sintering period, wherein the first reducing atmosphere is substantially devoid of nitrogen, and the first sintering period is at least about 15 minutes;
- and
- sintering the unsintered hot surface igniter body in a second reducing atmosphere at a second sintering temperature for a second sintering period, wherein the second reducing atmosphere is partially-nitrogenated, and the second sintering temperature is at least about 2400° C. during the second sintering period.
Dependencies are inferred from the claim text.