US2012897A - Process for increasing the electri - Google Patents
Process for increasing the electri Download PDFInfo
- Publication number
- US2012897A US2012897A US2012897DA US2012897A US 2012897 A US2012897 A US 2012897A US 2012897D A US2012897D A US 2012897DA US 2012897 A US2012897 A US 2012897A
- Authority
- US
- United States
- Prior art keywords
- magnesium oxide
- temperature
- oxide
- approximately
- heating
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000000034 method Methods 0.000 title description 12
- 230000008569 process Effects 0.000 title description 12
- 239000000395 magnesium oxide Substances 0.000 description 29
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 29
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 28
- 238000010438 heat treatment Methods 0.000 description 16
- 239000004020 conductor Substances 0.000 description 4
- 230000001590 oxidative effect Effects 0.000 description 4
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000004075 alteration Effects 0.000 description 2
- 238000010292 electrical insulation Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 1
- 239000001095 magnesium carbonate Substances 0.000 description 1
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052573 porcelain Inorganic materials 0.000 description 1
- 230000008707 rearrangement Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2/00—Lime, magnesia or dolomite
- C04B2/10—Preheating, burning calcining or cooling
- C04B2/102—Preheating, burning calcining or cooling of magnesia, e.g. dead burning
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
Definitions
- Our invention relates to electrical insulation and has for its object the provision of improved electrical insulation and process of making it. More specifically our invention relates to improvements in fused magnesium oxide.
- heaters of this type comprise a resistance conductor inclosed by a metallic sheath and insulated from it by a densely compacted layer of magnesium oxide, usually in powdered form.
- the insulating layer between the conductor and the sheath be comparatively thin so that the conductor is in intimate thermal relation with its inclosing sheath.
- the insulating layer possess suificient'electrical resistivity to thoroughly insulate the heater, and so, the thickness of the layer must not be reduced to such an extent that the insulation of the heater would be dangerously weakened.
- our invention contemplates the provision of an improved process for treating fused magnesium oxide whereby its electrical resistivity is materially increased.
- One of the beneficial results of our process is that for a given insulation requirement the thickness of the insulating layer is materially reduced, or in other words, for a given thickness of insulating layer, the electrical resistivity is considerably increased.
- our invention contemplates the provision of an improved process for treating fused magnesium oxide whereby its stability in the presence of moisture is increased.
- the fused magnesium oxide is heated or fired for a certain period of time, whereby certain chemical action or physical alteration takes place which increases the electrical resistivity of the oxide and its stability in the presence of moisture.
- Fused magnesium oxide used in electric heaters usually is made from magnesium carbonate, which when suitably treated by heat is reduced to magnesium oxide, and carbon dioxide which passes off as a gas.
- the magnesium oxide thus formed is fused in a suitable furnace or crucible at some suitable comparatively high temperature such as 5000 F.
- the fused magnesium oxide' which is made in this manner usually is in lump form, and to render it available for use, it is subjected to a crushing or grinding or like mechanical operation to reduce it to a comparatively fine powder. It is this powder which heretofore has generally been used to insulate electric heaters of the sheathed type.
- the magnesium oxide in order to increase the electrical resistivity of the fused magnesium oxide and moreover to increase its stability in the presence of moisture we heat or fire the magnesium oxide at a suitable temperature and for a certain period of time. While both the temperature at whichthe oxide is fired and the firing period may be varied, we have found that quite satisfactory results are obtained when the magnesium oxide is heated to a temperature of approximately 2100 F. and held at this temperature for approximately six hours. Preferably the oxide should be heated to this temperature at a comparatively slow rate, and likewise after this heating period the oxide should be allowed to cool at a comparatively slow rate. Satisfactory results will be obtained if the temperature of the oxide is gradually increased from room temperature to the heating temperature of 2100 F.
- the oxide is allowed to cool gradually for thirty or forty hours or more until it attains room temperature.
- These values may vary but for the most satisfactory results it is important that the magnesium oxide be brought up to its heating temperature at a comparatively slow rate, and likewise, that it be allowed to cool comparatively slowly after being heated.
- the heating temperature and the period of heating may be varied somewhat from the values mentioned above, but it is believed that the most satisfactory results will be obtained if the oxide is heated at an elevated temperature materially in excess of 1000 R, such as 2000-2300 F. and that it be heated for approximately six hours at this temperature. If a temperature lower than this range of 2000-2300 F. be used the oxide should 'be heated fora longer period of time.
- the fused magnesium oxide will be heated in a laboratory or commercial kiln used to fire porcelain or terra cotta or the like. Suitable containers, such as saggers, may be used to hold the magnesium oxide while it is being fired.
- the heating operation may be carried out either in an oxidizing or in a reducing atmosphere.
- impurities as iron and carbon are present, it is preferable to heat in an oxidizing atmosphere whereby these impurities are removed by As previously pointed out, 5
- a process for increasing the electrical resistivity of fused magnesium oxide which comprises heating said magnesium oxide in an oxidizing atmosphere for approximately six hours at a temperature of approximately 2000 F.-2300 F.
- a process for increasing the electrical resistivity of fused magnesium oxide which comprises heating said magnesium oxide from thirty to forty hours so that its temperature is gradually increased from room temperature to approximately 2000 F.-2300 F., maintaining the temperature of said oxide at approximately 2000 F.- 2300" F. for approximately six hours and then gradually cooling said magnesium oxide to room temperature through a period of approximately thirty to forty hours.
- a process for increasing the electrical resistivity of fused magnesium oxide and its sta- Whether the change is a surface condi-' bility in the presence ofmoisture whichcomprises heating said fused-magnesium oxide at a temperature of approximately 2000 F.-2300 F.
- a process for increasing the electrical resistivity of fused magnesium oxide and its stability in the presence of moisture which comprises heating said fused magnesium oxide in an oxidizing atmosphere at a temperature of approximately 2100 F. for approximately six hours.
- a process for increasing the electricalresistivity of fused magnesium oxide and its stability in the presence of moisture which comprises heating. said magnesium'oxide for thirty to forty hours so that its temperature is gradually increased from room temperature to approximately 2100 F., heating said oxide approximately at 2100 F. for approximately six hours and then allowing said magnesium oxide to gradually cool to room temperature through a period of thirty
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Compositions Of Oxide Ceramics (AREA)
- Resistance Heating (AREA)
Description
Patented Aug. 27, 1935 PROCESS. FOR INCREASING THE ELECTRI- CAL RESISTANCE OF FUSED MAGNESIUM OXIDE Robert J. Sutton, Wooster, Ohio, and Jonathan R. Fritze, Western Springs, Ill., assignors to Edison General Electric Appliance Company,
Inc.,
Chicago, Ill., a corporation 01 New York No Drawing. Application October 11, 1932, Serial No. 637,364
6 Claims.
Our invention relates to electrical insulation and has for its object the provision of improved electrical insulation and process of making it. More specifically our invention relates to improvements in fused magnesium oxide.
One common use of this material is to electrically insulate the resistance conductors and terminals of sheathed electric heaters of the type described and claimed in United States Patcnt No. 1,367 ,341 to C. C. Abbott, dated February 1, 1921. As there described, heaters of this type comprise a resistance conductor inclosed by a metallic sheath and insulated from it by a densely compacted layer of magnesium oxide, usually in powdered form.
It is desirable that the insulating layer between the conductor and the sheath be comparatively thin so that the conductor is in intimate thermal relation with its inclosing sheath. However, it is important that the insulating layer possess suificient'electrical resistivity to thoroughly insulate the heater, and so, the thickness of the layer must not be reduced to such an extent that the insulation of the heater would be dangerously weakened.
In one of its aspects our invention contemplates the provision of an improved process for treating fused magnesium oxide whereby its electrical resistivity is materially increased.
One of the beneficial results of our process is that for a given insulation requirement the thickness of the insulating layer is materially reduced, or in other words, for a given thickness of insulating layer, the electrical resistivity is considerably increased.
In another of its aspects our invention contemplates the provision of an improved process for treating fused magnesium oxide whereby its stability in the presence of moisture is increased.
In accordance with our invention the fused magnesium oxide is heated or fired for a certain period of time, whereby certain chemical action or physical alteration takes place which increases the electrical resistivity of the oxide and its stability in the presence of moisture.
Fused magnesium oxide used in electric heaters usually is made from magnesium carbonate, which when suitably treated by heat is reduced to magnesium oxide, and carbon dioxide which passes off as a gas. The magnesium oxide thus formed is fused in a suitable furnace or crucible at some suitable comparatively high temperature such as 5000 F. The fused magnesium oxide' which is made in this manner usually is in lump form, and to render it available for use, it is subjected to a crushing or grinding or like mechanical operation to reduce it to a comparatively fine powder. It is this powder which heretofore has generally been used to insulate electric heaters of the sheathed type. in order to increase the electrical resistivity of the fused magnesium oxide and moreover to increase its stability in the presence of moisture we heat or fire the magnesium oxide at a suitable temperature and for a certain period of time. While both the temperature at whichthe oxide is fired and the firing period may be varied, we have found that quite satisfactory results are obtained when the magnesium oxide is heated to a temperature of approximately 2100 F. and held at this temperature for approximately six hours. Preferably the oxide should be heated to this temperature at a comparatively slow rate, and likewise after this heating period the oxide should be allowed to cool at a comparatively slow rate. Satisfactory results will be obtained if the temperature of the oxide is gradually increased from room temperature to the heating temperature of 2100 F. through a heating period of thirty or forty hours or more and after heating, the oxide is allowed to cool gradually for thirty or forty hours or more until it attains room temperature. These values may vary but for the most satisfactory results it is important that the magnesium oxide be brought up to its heating temperature at a comparatively slow rate, and likewise, that it be allowed to cool comparatively slowly after being heated.
The heating temperature and the period of heating may be varied somewhat from the values mentioned above, but it is believed that the most satisfactory results will be obtained if the oxide is heated at an elevated temperature materially in excess of 1000 R, such as 2000-2300 F. and that it be heated for approximately six hours at this temperature. If a temperature lower than this range of 2000-2300 F. be used the oxide should 'be heated fora longer period of time.
On the other hand, if a higher temperature be used the heating period should be shortened accordingly.
Preferably the fused magnesium oxide will be heated in a laboratory or commercial kiln used to fire porcelain or terra cotta or the like. Suitable containers, such as saggers, may be used to hold the magnesium oxide while it is being fired.
The heating operation may be carried out either in an oxidizing or in a reducing atmosphere. When such impurities as iron and carbon are present, it is preferable to heat in an oxidizing atmosphere whereby these impurities are removed by As previously pointed out, 5
' oxidation. In such cases we have found that very satisfactory results are obtained by heating in air.
It is not understood definitely what happens to the fused magnesium oxide by the above treatment. tion, chemical alteration, or an 'intemal rearrangement of molecules is not known. It is known, however, that the electrical resistivity of the oxide is materially increased by our process. In certain instances, the electrical reslstivity'of the oxide has been increased more than 300%, even as high as 1000%. Moreover, it is known that the stability of the magnesium oxide in the presence of moisture is definitely increased.
What we claim as new and desire to secure by Letters Patent of the United States is:
1. A process for increasing the electrical resistivity of fused magnesium oxide which comprises heating said magnesium oxide in an oxidizing atmosphere for approximately six hours at a temperature of approximately 2000 F.-2300 F.
2. A process for increasing the electrical resistivity of fused magnesium oxide which comprises heating said magnesium oxide from thirty to forty hours so that its temperature is gradually increased from room temperature to approximately 2000 F.-2300 F., maintaining the temperature of said oxide at approximately 2000 F.- 2300" F. for approximately six hours and then gradually cooling said magnesium oxide to room temperature through a period of approximately thirty to forty hours.
3. A process for increasing the electrical resistivity of fused magnesium oxide and its sta- Whether the change is a surface condi-' bility in the presence ofmoisture whichcomprises heating said fused-magnesium oxide at a temperature of approximately 2000 F.-2300 F.
' for approximately six hours.
4. A process for increasing the electrical resistivity of fused magnesium oxide and its stability in the presence of moisture which comprises heating said fused magnesium oxide in an oxidizing atmosphere at a temperature of approximately 2100 F. for approximately six hours.
5. A process for increasing the electricalresistivity of fused magnesium oxide and its stability in the presence of moisture which comprises heating. said magnesium'oxide for thirty to forty hours so that its temperature is gradually increased from room temperature to approximately 2100 F., heating said oxide approximately at 2100 F. for approximately six hours and then allowing said magnesium oxide to gradually cool to room temperature through a period of thirty
Publications (1)
Publication Number | Publication Date |
---|---|
US2012897A true US2012897A (en) | 1935-08-27 |
Family
ID=3427315
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US2012897D Expired - Lifetime US2012897A (en) | Process for increasing the electri |
Country Status (1)
Country | Link |
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US (1) | US2012897A (en) |
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- US US2012897D patent/US2012897A/en not_active Expired - Lifetime
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