US2414369A - Vitreous and vttrifiable composi - Google Patents

Description

Patented Jan. 14,?1h47 I v v UNITE STATES PATENT OFFICE vrrmzous AND T VITRIFIABLE' COMPOSI- rrons or MATTER AND METHODS, or MAKING THE SAME f Harold R. Felchter, Canton, Ohio, assignor to United States Quarry Tile Company, Canton, Ohio, a corporation of Delaware No Drawing. Original application August 27,

1942, Serial No. 456,414. Divided and this application May 27, 1946, Serial No. 672,691

r 1 Claim. (01. 106-66) l i I 2 The discovery and invention relate in general ductivity form as a satisfactory aircraftengine to compositions of matter for vitreous products spark plug insulator, and furthermore is subject andthe like, and for vitrifiable bodies and the to attack by the lead compounds present in the like, and methods of making the same. combustion gases of high octane tetraethyl lead l The discovery and invention particularly relate 5 gasolines. l to substances requiring high temperatures for Mullite porcelains, composed chiefly of clay and vitrification, and more particularly to .composisilica minerals, uch as sillimanite, fired together L tions of matter including aluminum oxide, and at a temperature of approximately 2700 F., dethis application is a division of my application, velop into strong crystalline structures having Serial No. 456,414, filed August 27, 1942. 1o improved m chani al str n th and m v d t Products made by vitrifying or-vfiring at high dielectric strength as compared to ordinary portemperatures, body compositions having a their celains, but still lacking Suflicient thermal conprincipal constituent aluminum oxide are used ductivity and chemical stability necessary for use as spark plug insulators, particularly for aircraft as spark plug insulators in high compression engines, wear resistant and similar parts having air raft motors.

extreme hardness, and for other purposes. It has been determined to be desirable for'use Spark plug insulators adapted for use in a high as spark plug insulators in high compression aircompression internal combustion engine such as craft motors to providea fired composition of an aircraft engine or motor become increasingly matter having the greatest attainable combinadiflicult to produce, the higher the compression 2o tlon of .the following properties.

of the 'engineand the tendency is always to in- 1. Vitreousness to a high degree and ext e y crease the compression of an aircraft engine 10W P t whenever possible. 2. Hot dielectric strength in excess of 100 meg- Mica has been used for the insulators of air- Ohms at 1000 F.; craft engine spark plugs, but most mica having 3. Resistance to thermal shock so as not to be the required special mineral and physical proper- Subject t fracture when q c d n Water at ties must be imported into the United States, room t mp tu e m a t mp ratur f 400 R: the forming and machining of mica insulators 4. Mechanical strength greater than 100,000 is relatively costly, and the quality of mica insu- 1738- D q. in p ss lators is not always satisfactory. he al expansion of '7.00 1 Mica being a natural mineral and containing High thermal conductivi y; a varying amount of chemically combined water 7. Hardness and resistance to wear such that of crystallization in its composition, tends to dehe har ness is 9 or over on Mohs scale; compose when heated giving up its water of crys- 4 Inert-With common acids at normal p tallizationand deteriorating incrystalline form times, that is not Subject to appreciable lo s in to that of an anhydrous powder, and thus de- 6' or cold HCL' 2 4, a, '01 H3PO'4;

teriorates rapidly from its initial characteristics 9. Resistant to corrosion in molten lead oxide; when used as a spark plug insulator in a high j 10. AbSOIPtiVeOf radiant ycompression enginef Pure aluminum oxide has been found to attain With the development of higher compression 40 a combination of the above pr p rties satisfactory motors, mica becomes increasingly unsatisfactory for use In the vitrified state as insulators for airas an insulator for the spark plugs 'for the mocraft engin Spa p tors. and other substances have been used ine Co e cial production of vitrified articles eluding ordinary porcelain and mullite porcelain. f P e alumlnum de, 0r a u ina, has not Ordinary porcelain, such as a composition of e found practicable because 0f the extremely feldspar, pure clay, and flint fired to a temperahigh temperatures requir d to bring about the ture of 2300" to 2500 F., constitutes a superior eendense-tien 0 a pu e alumina body to the form of burned clay product, but for spark plug point of complete vitreousness free from porosity, insulator use has relatively poor resistance to and because the lack of plasticity of pure alumina the thermal shock imposed upon thespark plug renders its formation as a body into any particuinsulators of a high compression motor. lar shape such as that of an insulator'very dif- Furthermore ordinary porcelain has a low dificult. 7

electric .strength, particularly when hot, and is- By the present discovery and invention, it has in fact an electrical conductor when hot.- Ordibeen found that the presence of a very small nary porcelain also has insufilcient thermal conamount 01' substantially any other inorganic sub-- stance in a otherwise including substan-, tiaily all alumina will produce a pronounced'depression in'the temperature necessary for the vitrification of the body composition. and

improve-the forming adaptability. .It has further beendiscovered that a combination of a relatively great variety of other 'sub- I stances to a total f-a verysmallamount in a body, the remalnderof which is'substantially all alumina, has amore pronounced effect in depressing the vitrification temperature than when only one or two other substances with-alumina are used for the body; I

It has further been discovered that by using a combination. of four or more other substances I with alumina in the body, that thetotal amount of the added substances can be kept very low in proportion to the alumina and that in this way the properties of the body and the fired product are predominantlythose of alumina, and stability is attained in the production of the fired products without the sacrifice of any substantial amount of the desired properties of the major ingredient al Plotting the eilects of the various added substances on a phase rule diagram reveals a leveling oil of the effects through the combination of the various added ingredients, so that instead of sharp changes affecting the combination, the

changes are more gradual and the firing range of the combination is greatly extended and stabiermore, the addition of a relatively great variety of substances to the predominant alumina provides a factor of safety against the variations that normally exist in the commercial forms of the substances, so that a more stable and dependable body is obtained through the use in the body composition of a wide variety of substances added to the alumina. g

' Also it has been discovered that regardless of the specified siih tenee added to the alumina, if added in minute amount, the eilect on the alumina will be about in the same degree. The I alumina in the resultant mixture or .body is overwhel l ly the predominant material, and the resultant body has substantially the properties of that of pure alumina.

In attaining a combination of the highest degree of the above enumerated properties for a room temperature. 7 Without the chromium oxide the fired articles are white in color. The strong pink or rose color produced in the fired article by the chromium oxide changes when hot, as when the articleis in use as an insulator in an aircraft engine spark plug, to black which imabsorption by the absorption of radiant heat from the gases of combustion in the engine cylinder; theradiant heat being otherwise reflected bywhite or coated bodies.

To the predominant alumina, the chromium 7o oxide is added and small quantities of other substances selected from a wide variety of metallic oxides and compounds.

The total amount of the added substances should preferably not exceed 8% of the composition, the remaining 92% being alumi It is preferable that the total number or added substances be more than three.

' All-the added substances are selected from the followingmetals in their oxide or other compound forms:

Mercury Aluminum Antimony Molybdenum Arsenic Nickel Barium Osmium Beryllium v 'Plahnum Bismuth Potassium Boron Praseodymium Cadmium Rubidium 'Caesium Sc'andium Calcium g Selenium Cerium Silicon Chromium Silver Cobalt Sodium Columbium Strontium Copper Tantalum Dysprosium Thallium Gallium -Thorium Germanium Tin Gold Titanium Indium Tlmgsten Iridium Tellurium Iron I Uranium Lanthanum Vanadium I Lead Yttrium Lithium Zinc Magnesium Zirconium Manganese The above metals are included in groups 1 2, v 1' 3, 4, 5, 6, 7, -8 of the periodic table of elements of matter.

' While it has been found that the presence of the alkaiis of group 1 of the periodic table of elements, particularly sodium and potassium, are deleterious to the fired composition in causing a reduction in hot dielectric strength, it is a practi-' cal impossibility to avoid traces to measurable amounts of these substances in the Furthermore, it has been found that a proportion of these alkalis not in excess of 0.05%"

does not sufllciently deteriorate the body dielec- .tricaiiy to cause any seriously harmful results, and that their presence in combination withother substances, particularly the alkaline earths of group 2 of the periodic table of elements and boron, develops low fusion combinations and intensifies the fluxing action of-the mass. Therefore allowance for the presence of these alkaline substances is made in the particular body compositions of the present discovery and invention.

The alumina in the body composition or mixture should be in excess of 92% and preferably in excess of 95%. It has been found impractical so from a firing standpoint to vitrify mixtures much in excess of 95% alumina. However the properties of the product are much improved as the alumina is increased, and laboratory products.

have been made at temperatures of 3400 F. in

parts to the insulator the property of greater heat which p si ons i h 88 of alumina were vitrified, yielding an excellent product, but

' impractical to produce in. commercial practice atpresent because of 'the exceedingly high temperature required.

The silica content of the body is minimized by t tal avoiding silica contamination in the processing,

aeiaseo body composition. 'Where calcium, magnesium, chromium, beryllium. and barium are used in the body composition, the forms of these substances may be in the compounds including fluorides, 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 potassium.

However, by the introduction of fluorides into the body composition, silicates of the metals, such as magnesium in the form of talc may be used to a limited extent without harmful results from subsequent silica contamination, because the fluorine set free by the reaction resulting from the firing of the body composition combines with the silica to form gaseous silicon tetrafluoride whichescapes'and constitutes a volitilization of the silicon.

Describing one particular composition .of matter or Body Composition I of the discovery and. invention and the method of, making the same, the principal ingredient of the body composition is calcined aluminum oxide, which before use in the compounding of the body is highly refined and. freed of soluble impurities by lixiviation after being ground to a sub-microscopic grain size.

. and by using silicates as little es possible in the i the second firing to a temperature of over 8000' To 92 parts by weight of this purified and finely ground alumina A110: is added and thoroughly scopic grain size, quartz stones are generally used as grinding media, and in the grinding the abrasiveness of the calcined alumina on the quartz grinding stones causes about 1 /2 to 2% of silica to be ground into the alumina so that the alumina after grinding has a composition of 98 to 98%% A120: and 1% to 2% 810:.

In the preferred manner'of grinding the alumm. for the bodies of the present invention, a rubber lined mill is used, and the grinding balls are formed. of fired alumina, thereby avoiding the pick-up of silica in the ground alumina.

It has further been discovered that the initial calcination of the fluxing ingredients alone or in combination with part or all of the alumina is desirable before the final body is formed and the final firing effected. r

' -Eutectics, are formed between alumina and a Per cent Alumina, aluminum oxide 92.25 Talc, magnesium silicate 1.25 V Fluorspar, calcium fluoride 2.00 i Clay, aluminum silicate 3.50

Chromium oxide Body composition III Per cent Alumina, aluminum oxide 91.88 Talc, magnesium silicate 1:25 Whiting, calcium carbonate.-. 2.5!

Clay, aluminum silicate 3.50 Chromium oxide 1.00

Body composition IV Per cent Alumina, aluminum oxide 92.04 Talc, magnesium silicate 1.25 Barium carbonate -s. 0.89 -Whiting, calcium carbonate .0.44

F., produces a fired product consisting of alumip num in excess of 92%, and the oxides of the added metals, silicon, calcium, chromium, and magneslum, the fired product having desired properties Body compositimi I1 Clay, aluminum silicate-.. 3.50 Chromium oxide 1.00 Beryllium silicate -1..- 0.88

The embodiments of the compositions of matter and the method steps of making the same described herein are by way of example, and the scope of the prevent discovery and invention is combination of various other substances. However the formation of these eutectics requires initially a very high temperature, at which point 7 the firing range of the mixture is very short due composition, upon the second heating, the sin-.

tering point is reached at a much lower temperature because of the previously formed eutectics.

A combination of many ingredients yields a.

superior result than when only few are used, since the eutectics formed between alumina and a wide variety of substances in combination provides a D wide range of'temperature over which the varnot limited to the same or to the particular details thereof, but is commensurate with any and all novel subject matter contained herein which may at any time properly under the United States patent laws be set forth in the claim hereof or originating herein, and the elements of any such claim are intended to include their reasonable equivalents.

-' Iclaim: i

. A body composition of matter, for a fired vitreous product, including the following compounds, mixed in parts by weight:

1 Alumina, aluminum oxide- 92.04 Talc, magnesium silicate 1.25 Barium carbonate 0.89 Whiting, calcium carbonate"; 0.44

Clay, aluminum silicate 8.50 Chromium oxide 1.00 Beryllium silicate 0.88

' HAROLD B. IEICHTER-