2,413,441 Patented Dec. 31, 1946 UNITED STATES PATENT OFFICE 2,413,441 'VITREOUS AND VITRIFIABLE COMPOSI TIONS 0F MATTER AND METHODS OF MAKING THE SAME ‘Harold R. Feiehter, Canton, Ohio, assignor to United States Quarry Tile Company, Canton, Ohio, a corporation of Delaware ' No Drawing. Application August 27, 1942, Serial No. 456,414 1 Claim. (Cl. 106-66) 1 2 to attack by the lead compounds present in the combustion‘ gases of high octane tetra ethyl lead The discovery and invention relate in general to compositions of matter for vitreous Products and the like, and for vitri?able bodies and the gasolines. Mullite porcelains, composed chie?y of clay and like, and methods of making the same. The discovery and invention particularly re silica minerals, such as sillimanite, ?red together at a temperature of approximately 2700” F., de-v velop into strong crystalline structures having im late to substances requiring high temperatures , for vitri?cation, and more parti?ularly t0 compo proved mechanical strength and improved hot di electric strength as compared to ordinary porce lains, but still lacking su?icient thermal conduc tivity and chemical stability necessary for use as spark plug insulators in high compression aircraft motors. sitions of‘ matter including aluminum oxide. Products made by vitrifying or ?ring at high temperatures body compositions having as their principal constituent aluminum oxide are used as spark plug insulators, particularly for aircraft engines, wear resistant and similar parts having It has been determined to be desirable for use extreme hardness, and for other purposes. Spark plug insulators adapted for use in a high 15 as spark plug insulators in high compression air -craft motors to provide a ?red composition of compression internal combustion engine such as matter having the greatest attainable combina an aircraft engine or motor become increasingly tion of the following properties: . di?icult to produce, the higher the compression 1. vitreousness to a high degree and extremely of the engine, and the tendency is always to in ‘ crease the compression of an aircraft engine 20 low porosity; 2. Hot dielectric strength in excess of 100 meg whenever possible. ‘ Y . ohms at 1000° F.; Mica has been'used for the insulators of air 3. Resistance to thermal shock so as not to be craft engine spark plugs, but most mica having subject to ‘fracture when quenched in water at the required special mineral and physical prop room temperature from a temperature of 400° F.; erties must be imported into the United States, 4. Mechanical strength greater ‘than 100,000 the forming and machining of mica insulators is relatively costly, and the quality of mica insular _ lbs. per sq. in. in compression; 5. Thermal expansion of 7.00x10-“; tors is not always satisfactory. Mica being a natural mineral and contain ing a varying amount of chemically combined wa ter of crystallization in its composition, tends to decompose when heated giving up its water of crystallization and deteriorating in crystalline 6. High thermal conductivity; 30, 7. Hardness and resistance to wear such that the hardness is 9 or over On Mohs’ scale; 8. Inert with common acids at normal temper atures, that is notsubj'ect to appreciable loss in form to that of an anhydrous powder, and thus . hot or cold HCl, H2SO4,‘HNO3, or ,HaPOr; ' deteriorates rapidly from its initial characteris 35 9. Resistant to corrosion in molten lead oxide; 10. Absorptive Of radiant energy. ' tics when used as a spark plug insulator in a. high compression engine. v Pure aluminum oxide has been found to attain a combination of the above properties satisfactory for use in the vitri?ed state as insulators for air tory as an insulator for the spark plugs for the 40 craft engine spark plugs. The commercial production ofvitri?ed articles motors, and other substanceshave been used in With the development of higher compression motors, mica becomes increasingly unsatisfac cluding ordinary porcelain and mullite porcelain. Ordinary porcelain, such as a composition of feldspar, pure clay, and ?int ?red to a tempera ture of 2300" to 2500° F., constitutes a superior form of burned clay product, but for spark plug I from pure aluminum oxide, or alumina, has not been found practicable because of'the extremely " high temperatures required to bring about the condensationof a purealumina body to the point of complete vitreousness freev from porosity, and because the lack of plasticity of pure alumina ren insulator use has relatively poor resistance to the ders its formation as a body into any particular thermal shock imposed upon the spark plug insu shape such as that of an insulator very di?icult. lators of a high compression motor. By the present discovery and invention, it has Furthermore ordinary porcelain has a low di 50 been found that the presence of a very small electric strength, particularly when hot, and is in fact an electrical conductor when hot. " Ordi amount of substantially any other'inorganic sub nary porcelain also has insu?icient thermal con ductivity for use as a satisfactory aircraft engine stance in a body otherwise including substantially all alumina will produce a pronounced depression spark plug insulator, and furthermore is subject in the temperature necessary fcrthe vitri?cation 2,413,441 3 4 of the body composition, and will improve the It is preferable that the total number of added forming adaptability. substances be more than three. All the added substances are selected from the following metals in their oxide or other compound forms: It has further been discovered that a combina tion of a relatively great variety of other sub stances to a total of a very small amount in a body, the remainder of which is substantially all Aluminum Mercury Arsenic only one or two other substances with alumina 10 Barium are used for the body. Beryllium It has further been discovered that by using a Bismuth combination of four or more other substances Nickel Osmium alumina, has a more pronounced e?ect in de pressing the vitri?cation temperature than when _ Antimony Boron with alumina in the body; that the total amount Cadmium of the added substances can be kept very low in proportion to the alumina and that in this way 15 Caesium Calcium the properties of the body and the ?red product Cerium are predominately those of alumina, and stability Chromium is attained in the production of the ?red prod Cobalt ucts without the sacri?ce of any substantial amount of the desired properties of the major in 20 Columbium gredient alumina. > ' Plotting the eil'ects of the various added sub stances on a phase rule diagram reveals a level Copper Dysprosium Gallium Germanium ling of! of the effects through the combination of the various added ingredients, so that instead of 25 Gold Indium sharp changes affecting the combination, the Iridium changes are more gradual and the firing range of Iron the combination is greatly extended and sta Molybdenum Platinum Potassium Praseodymium Rubidium Scandium Selenium silicon Silver Sodium Strontium Tantalum Thailium Thorium Tin Titanium Tungsten Tellurium Uranium lanthanum Vanadium , bilised. Yttrium Furthermore, the addition of a relatively great 30 Lead Lithium Zinc ' ‘ variety of substances to the predominant alumina Magnesium Zirconium provides a factor of safety against the variations Manganese that normally exist in the commercial forms of the substances, so that a more stable and de The above metals are included in groups 1, 2, 3, pendable body is obtained through the use in the 35 4, 5, 6, '1, 8 of the periodic table of elements of body composition of a wide variety of substances matter. added to the alumina. While it has been found that the presence of Also it has been discovered that regardless of the alkalis of group 1 of the periodic table of the speci?ed substance added to the alumina, if 40 elements, particularly sodium and potassium, are added in minute amount, the effect on the alu mina will be about in the same degree. The alumina in the resultant mixture or body is over whelmingly the predominant material, and the resultant body has substantially the properties of that of pure alumina. In attaining a combination of the highest de gree of the above enumerated properties for a deleterious to the ?red composition in causing a reduction in hot dielectric strength, it is a prac tical impossibility to avoid traces to measurable amounts of these substances in the body. Furthermore, it has been found that a pro portion of these alkalis not in excess of 95% does not sufficiently deteriorate the body dielectrically to cause any seriously harmful results, and that their presence in combination with other sub engine spark plug insulators, it has been found stances, particularly the alkaline earths of group 50 preferable to use body combination of aluminum 2 of the periodic table of elements and boron, oxide with the addition of chromium oxide in a develops low fusion combinations and intensi?es minor quantity plus the addition of small quan the ?uxing action of the mass. Therefore allow titles of other inorganic substances preferably the ance for the presence of these alkaline substances oxides of the other metals. ' is made in the particular body compositions of In particular the chromium oxide produces in 55 the present discovery and invention. > the ?red article a strong pink or rose color at The alumina in the body composition or mix room temperature. Without the chromium oxide ture should be in excessof 92% and preferably the ?red articles are white in color. The strong in excess of 95%. It has been found impractical from a ?ring standpoint to vitrify mixtures much pink or rose color produced in the ?red article in excess of 95% alumina. However the proper by the chromium oxide changes when hot, as ties of the product are much improved as the when the article is in use as an insulator in an alumina is increased, and laboratory products aircraft engine spark plug, to black which im have been made at temperatures of 3400' I". in parts to the insulator the property of greater heat which compositions as high as 98% of alumina absorption by the absorption of radiant heat from were vitri?ed, yielding an excellent product, but the gases of combustion in the engine cylinder, impractical to produce in commercial practice the radiant heat being otherwise reflected by at present because of the exceedingly high tem white or coated bodies. perature required. To the predominant alumina, the chromium The alumina is preferably in excess of 99% oxide is added and small quantities of other sub 70 A120: and as stated free from alkalis in excess stances selected from a wide variety of metallic ¢Bf5ég5% and also free from silica in excess of oxides and compounds. The total amount of the added substances The silica content of the body is minimisedby should preferably not exceed 8% of the total avoiding silica contamination in the processing, ?red composition of matter for use as aircraft composition, the remaining 92% being alumina, 76 andbyusingsilicatesaslittleaspossibleinthe 9,413,441 6 various eutectics are active, whereas with a lesser body composition. Where calcium, magnesium, number, the range is correspondingly shorter. The above described Body Composition I after chromium, beryllium, and barium are used in the body composition, the forms of these substances may be in the compounds including fluorides,’ the second ?ring to a temperature of over 3000° F., produces a ?red product consisting of alumi num in excess of 92 %, and the oxides of the added carbonates, oxides, phosphates, sulphates, etc., to avoid the silicates. All the added substances should be preferably in the dehydrated form, and free from the alkalis, lithium, sodium, and potas metals, silicon, calcium, chromium, and magnesi um, the ?red product having desired properties as set forth herein for use as an aircraft spark sium. However, by the introduction of fluorides into 10 plug insulator, and other purposes. Examples of other body compositions, made the body composition, silicates of the metals, such according to the present discovery and invention, as magnesium in the form of talc may be used to and processed as set forth herein to produce the ya limited extent without harmful results from improved ?red product including alumina and subsequent silica contamination, because the flu orine set free by the reaction resulting from the 15 other metallic oxides, are as follows: ?ring of the body composition combines with the Body Composition II silica to form gaseous silicon tetra?uoride which escapes and constitutes a volatilization of the silicon. Describing one particular composition of mat ter or Body Composition I of the discovery and invention and the method of making the same, the principal ingredient of the body composition Per cent Alumina, aluminum oxide _____________ __ 92.25 Talc, magnesium silicate _______________ __ 1.25 20 Fluorspar, calcium fluoride _____________ .. 2.00 Clay, aluminum silicate ________________ __ 3.50 Chromium oxide ______________________ __ 1.00 is calcined aluminum oxide, which before use in the compounding of the body is highly re?ned and freed of soluble impurities by lixiviation after being ground to a sub-microscopic grain size. To 92 parts by weight of this puri?ed and ?nely ground alumina A1203 is added and thor oughly mixed 11/2 parts of calcium ?uoride CaFz and 1 1/2 parts magnesium phosphate Mg: (P04) 2.4H2O 4 parts of plastic ball clay ahoazsioaznzoand 1 part of chromic oxide CraOa. In the grinding of the alumina to sub-micro 25 100.00 Body Composition III Per cent Alumina, aluminum oxide ______________ __ 91.68 Talc, magnesium silicate _______________ _. 1.25 30 Whiting, calcium carbonate ____________ __ 2.57 Clay, aluminum silicate ________________ __ 3.50 Chromium oxide 1.00 ' 35 scopic grain size quartz stones are generally used as grinding media, and in the grinding the abra siveness of the calcined alumina on the quartz grinding stones causes about 11/2 to 2% of silica to be ground into the alumina so that the alumina 40 after grinding has a composition of 98 to 981/2% A120: and 11/2 to 2% SiOz. In the preferred manner of grinding the alumi na for the bodies of the present invention, a . 100.00 Body Composition IV Per cent Alumina, aluminum oxide ______________ __ 92.04 Talc, magnesium silicate _______________ __ 1.25 vBarium carbonate _____________________ __ 0.89 Whiting, calcium carbonate ____________ __ Clay, aluminum silicate ________________ __ 0.44 3.50 Chromium oxide _____________________ __ Beryllium silicate _____________________ __ 1.00 0.88 100.00 are formed of ?red alumina, thereby avoiding the The embodiments of the compositions of matter pick-up of silica in the ground alumina. and the method steps of making the same de It has further been discovered that the initial scribed herein are by'way of example, and the calcination of the ?uxing ingredients alone or in scope of the present discovery and invention is 50 combination with Part or all of the alumina is not limited to the same or to the particular de desirable before the ?nal body is formed and the tails thereof, but is commensurate with any, and ?nal ?ring effected. ' all novel subject matter contained herein which rubber‘ lined mill is used, and the grinding balls Eutectics are formed between alumina and a may at any time properly under the United States combination of various other substances. How patent laws be set forth in the claims hereof or ever the formation of these eutectics requires ini originating herein, and the elements of any such tially a very high temperature, at which point the claims are intended to include their reasonable ?ring range of the mixture is very short due to equivalents. the sudden depression of the melting point at the I claim: temperature of the formation of the eutectics. A body composition. of matter, for a ?red When however the mixture is fused or calcined 60 vitreous product, including the following com and then ground and re-f‘ormed, as the ?nal body pounds in parts by weight: composition, upon the second heating, the sinter Alumina, A1201 92 ing point is reached at a much lower temperature ' because of the previously formed eutectics. A combination of many ingredients yields a Calcium ?uoride, CaF: ___________________ __ 1.5 Magnesium phosphate, Mga(PO4)2.4HzO_____ 1.5 superior result than when only few are used, since Plastic ball clay, A1203.2S102.2H2O ________ __ 4 the eutectics formed between alumina and a wide variety of substances in combination pro vides a wide range of temperature over which the Chromic oxide, CraO: ____________________ .... 1 HAROLD R. FEICHTER.