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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 c

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.

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1. 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 preen density of greater than 70 percent of a theoretical maximum density; sintering the unsinter

1. 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 preen density of greater than 70 percent of a theoretical maximum density; sintering the unsintered hot surface igniter body in a reducing atmosphere comprising nitrogen in an amount ranging from 20 mole percent to 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 five (5) percent, said sintering the unsintered hot surface igniter body in a reducing atmosphere comprises sintering the hot surface igniter body at one or more first sintering temperatures ranging from 2075° C. to 2425° C. for a first sintering period of from 20 minutes to 150 minutes, and said sintering the unsintered hot surface igniter body in the reducing atmosphere during the first sintering period further comprises (i) sintering the unsintered hot surface body igniter at a first sintering temperature of at least 2075° C. during a subperiod at east 40 minutes in the reducing atmosphere, and (ii) sintering the unsintered hot surface igniter body at a first sintering temperature of at least 2400° C. for a subperiod of at least about 15 minutes in the reducing atmosphere. 2. The method of claim 1, wherein the green density is less than 95 percent of the maximum theoretical density. 3. The method of claim 1, wherein the silicon carbide in the unsintered hot surface igniter body comprises a fines portion and a coarse portion, and the coarse portion comprises at least 20 percent by weight of the silicon carbide in the unsintered hot surface igniter body. 4. The method of claim 1, wherein the reducing atmosphere further comprises a noble gas. 5. The method of claim 1, wherein the step of sintering the unsintered hot surface igniter body in the reducing atmosphere further comprises sintering the unsintered hot surface igniter during a second sintering period at a second sintering temperature of at least 2500° C. for a subperiod of at least about 40 minutes. 6. The method of claim 1, wherein the unsintered hot surface igniter body is free of any densification aids selected from the group consisting of boron carbide, boron nitride, aluminum carbide, carbon, beryllium oxide, hafnium oxide, and yttrium oxide. 7. The method of claim 1, wherein the sintered hot surface igniter body has a nitrogen content of from 500 ppm to 1500 ppm by weight of the sintered hot surface igniter body. 8. The method of claim 1, wherein the amount of silicon carbide in the sintered hot surface igniter body is at least 99 percent by weight of the sintered hot surface igniter body. 9. The method of claim 1, wherein the sintered hot surface igniter body has a negative temperature coefficient. 10. The method of claim 1, wherein the sintered hot surface igniter body has a porosity greater than seven (7) percent. 11. The method of claim 1, wherein the sintered hot surface igniter body consists essentially of silicon carbide, aluminum, iron, and nitrogen. 12. The method of claim 3, wherein the coarse portion has a D50 particle size of from 50 microns to 300 microns. 13. The method of claim 3, wherein the fines portion has a D50 particle size of from 0.5 microns to 10 microns. 14. The method of claim 8, wherein sintered hot surface igniter body comprises at least 200 ppm aluminum by weight of the sintered hot surface igniter body. 15. The method of claim 13, wherein the fines portion has a surface area of greater than 1 m2/g. 16. The method of claim 14, wherein the sintered hot surface igniter body comprises no more than 1000ppm of at least one transition metal by weight of the sintered hot surface igniter body. 17. 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 20 percent by weight of the silicon carbide in the unsintered hot surface igniter body, and the unsintered hot surface igniter body is free of any densification aids selected from the group consisting of boron carbide, boron nitride, aluminum carbide, carbon, beryllium oxide, hafnium oxide, and yttrium oxide; sintering the unsintered hot surface igniter body in a partially-nitrogenated reducing atmosphere at one or more first sintering temperatures ranging from 2075° C. to 2425° C. for a first sintering period of from 20 minutes to 150 minutes, wherein said sintering the unsintered hot surface igniter body for a first sintering period further comprises sintering the unsintered hot surface igniter body at a first sintering period temperature of at least 2075° C. during a first subperiod of at least 40 minutes in the partially-nitrogenated reducing atmosphere: and sintering the unsintered hot surface igniter body during a second sintering period at a second sintering temperature of at least 2500° C. for a subperiod of at least 40 minutes in the partially-nitrogenated reducing atmosphere. 18. The method of claim 17, wherein the sintered hot surface igniter body has a nitrogen content of from 500 ppm to 1500 ppm by weight of the sintered hot surface igniter body. 19. The method of claim 17, wherein the amount of silicon carbide in the sintered hot surface igniter body comprises at least 99 percent by weight of the first composition. 20. The method of claim 17, wherein sintered hot surface igniter body comprises at least 200 ppm aluminum by weight of the sintered hot surface igniter body. 21. The method of claim 17, wherein the sintered hot surface igniter body comprises no more than 1000 ppm of at least one transition metal by weight of the sintered hot surface igniter body. 22. The method of claim 17, wherein the sintered hot surface igniter body has a negative temperature coefficient. 23. The method of claim 17, wherein the sintered hot surface igniter body has a porosity greater than seven (7) percent. 24. The method of claim 17, wherein the sintered hot surface igniter body consists essentially of silicon carbide, aluminum, iron, and nitrogen. 25. The method of claim 17, wherein the unsintered hot surface igniter body has a green density of greater than 70 percent of a theoretical maximum density. 26. The method of claim 17, wherein the unsintered hot surface igniter body has a green density, and the sintered hot surface igniter body has a density that differs from the green density by no more than five (5) percent. 27. 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 15 minutes; andsintering 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 2400° C. during the second sintering period, the proximal region of the unsintered hot surface igniter body further comprises at least one transition metal silicide, the distal region of the unsintered hot surface igniter body is devoid of transition metal silicides, and the amount of the at least one transition metal silicide in the proximal region is from two percent to twenty percent by weight of the proximal region of the unsintered hot surface igniter body. 28. The method of claim 27, wherein during the first sintering period the first sintering temperature is at least 2000° C. during a subperiod of at least 30 minutes. 29. The method of claim 28, wherein during the first sintering period, the first sintering temperature is no greater than 2525° C. 30. The method of claim 27, wherein the second sintering period is at least 10 minutes. 31. The method of claim 27, wherein the sintering step further comprises sintering the unsintered hot surface igniter body during a third sintering period in the partially-nitrogenated second reducing atmosphere, wherein the third sintering temperature is at least 2500° C. during a subperiod of at least 40 minutes within the third sintering period. 32. The method of claim 27, wherein the first reducing atmosphere comprises a noble gas, and the second partially-nitrogenated reducing atmosphere comprises the noble gas. 33. The method of claim 27, wherein the silicon carbide in the distal region of the unsintered hot surface igniter body comprises a fines portion and a coarse portion, and the coarse portion comprises at least 20 percent by weight of the silicon carbide in the distal region. 34. The method of claim 27, wherein the distal region of the sintered hot surface igniter body consists essentially of silicon carbide, aluminum, and nitrogen. 35. The method of claim 27, wherein the partially-nitrogenated second reducing atmosphere comprises at least 10 mole percent nitrogen and no more than 80 mole percent nitrogen based on the total composition of the second reducing atmosphere. 36. The method of claim 27, wherein the distal region has a high temperature resistivity at 1000° C. of from 0.8 ohm-cm to 3.5 ohm-cm. 37. The method of claim 33, wherein the coarse portion has a D50 particle size of from 50 microns to 300 microns. 38. The method of claim 34, wherein the proximal region of the hot surface igniter body consists essentially of silicon carbide, nitrogen, and at least one transition metal silicide or transition metal silicide former. 39. The method of claim 35, wherein the partially-nitrogenated second reducing atmosphere consists essentially of nitrogen and argon. 40. The method of claim 36, wherein the distal region has a room temperature resistivity of at least about 3 ohm-cm.