CA1196485A - Protoenstatite ceramic units and process for their preparation - Google Patents
Protoenstatite ceramic units and process for their preparationInfo
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- CA1196485A CA1196485A CA000410353A CA410353A CA1196485A CA 1196485 A CA1196485 A CA 1196485A CA 000410353 A CA000410353 A CA 000410353A CA 410353 A CA410353 A CA 410353A CA 1196485 A CA1196485 A CA 1196485A
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- silica
- weight
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- feldspath
- aluminum silicate
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- 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
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/16—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on silicates other than clay
- C04B35/20—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on silicates other than clay rich in magnesium oxide, e.g. forsterite
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- Chemical & Material Sciences (AREA)
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- Materials Engineering (AREA)
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- Organic Chemistry (AREA)
- Compositions Of Oxide Ceramics (AREA)
Abstract
A B S T R A C T
Protoenstatite ceramic units are prepared by com-pressing units of a mixture of 55 to 80 parts by weight of uncalcined demagnetized asbestos tailings with 22 to 44 parts by weight of a source of silica and from 0 to 17 parts by weight of fluxing agents and firing the units at 1250 to 1500°C.
Protoenstatite ceramic units are prepared by com-pressing units of a mixture of 55 to 80 parts by weight of uncalcined demagnetized asbestos tailings with 22 to 44 parts by weight of a source of silica and from 0 to 17 parts by weight of fluxing agents and firing the units at 1250 to 1500°C.
Description
BACKGROUND OF THE INVENTION
.
Steatite bodies are used primarily as high frequency insulating bodies in the electronic and electronic and electrical appliance industries and ~5 are characterized by their high dielectric strength over wide temperature ranges, low power loss in the high frequency field, a water absorption of less than one percent and a high impact or mechanical resistan-ce.
The common practice in the manufacture of steatite products consists in mixing silica-rich magnesium silicate rocks such as clinoenstatite crystals (talc) with small amounts o:E clay and a ceramic flux.
Typical steatite compositions presently available analyze as follows:
SiO2 MgO A L2 03 K2 Fe2 03 TiO2 CaONa20 BaO
% % gO % % % ~ % %
a) 64.74 28~24 4.45 1.03 0.83 0.03 0.25 0.43 --b) 61.7 29.23 2.55 0.05 1.22 0.03 0.05 0.11 5.16%
It will be seen that contrary to a), b) contains alka].ine earth oxide flux (BaO) which impro-ves dielectric properties. It will also be seen that the i.ron oxide content (Fe2O3) is relatively low in these compositions.
~64~35 It is also known that serpentine, particularly chrysotile asbestos contains the two most important constituents of steatite, namely, magnesiun oxide and silica: Appreciating the enormous amount of chrysotile asbestos tailings and residues present near every asbestos mine in the world appear highly desirable if a procedure could be found to use these tailings and residues in the manufacture of steatite compositions whereby a substantial reduction in cost would be achieved while at the same time creating a new use of these tailings and residues for which only limited use has been found. It will also be appre-ciated that asbestos fibers represent only about 5 by weight of the mined asbestos rock and thus the cost of the tailings and residues is already included in the selliny price of all asbestos fibers.
SUMMARY OF THF INVENTION
In accordance with the present invention there is provided a process for preparing proto-enstatite ceramics units which include steatite which comprises mixing uncalcined and demagnetized asbestos tai.lings with a source of silica and after compressing th:is mixture, the unit is sintered within a tempera~
ture range of from 1250 to 1500C.
The steatite ceramic units thus obtained possess many of the desirable physical characteristics of presently available steatites. More particularly the physical and electrical properties can vary extensi-vely depending on the amounts and the particule sizeof the starting materials and the sintering temperature.
DETAILED DESCRIPTION OF THE INVENTION_ Essentially, steatite falls in the proto-enstatite domain and contains the following ingre-dients as its main constituents: 2~-32% of MgO and 55-65% of SiO~, the remainder comprising aluninum oxide and ceramic fluxing agents. Ferric oxide and small amounts of other oxides may be present as impurities in the raw materials used.
It is also known that magnesium oxide, si-lica and iron oxide constitute the essential ingre-dients of asbestos tailings, the respective amounts varying ~ith the location of the mine. The following Table I illustrates the major elements in the asbestos tail:ings oE three diEferent mines TABLE I
~ine M~O SiO2 Fe2O3 OthersL.O.I.*
% ~6 %
~ ~0.80 35.~ 7.3 1.20 15.30 B 39.69 35.768.06 2.5~ 13.95 C 36.95 38.358.95 2.89 12.86 *loss on ignition It appears from Table I that asbestos tailings would not be suitable for the manufacture of steatite b~cause of their hiyh iron oxide content.
In accordance with the present invention there is provided a shaped mi~ture suitable for sinte-ring at a temperature of from 1250 to 1500C using demagnetized asbestos tailings as the essential ingre dients or, as the source of magnesium oxide and as par-tial source of silica.
More specifically, the shaped mixture compri-ses from 55 to 80 parts by weight of uncalcined and demagnetized asbestos tailings with 22 to 44.0 parts by weight of a source of silica, and from 0 to 17 parts by weight of fluxing agent. The mixture of the present inventi.on after sintering wlll provide a steatite body ~herein the percentages of MgO, SiO2 and Al203 fall within the limits prescribed for steatite compositions.
It will ~e observed that the percentage Fe2O3 content of asbestos tailings has been reduced first ~y the magnetic separation step and secondly ~y the addition of the source of silica, the latter contributing also to the reduct:ion o:E the MgO and the increase of sio2 to within the prescribed limits Eor steatite composi-tions. The remainder of the composition will be made up of the impurities normally found in demagnetized asbestos tailings.
~6~5 Furthermore, depending on the source of silica used, certain useful fluxing agents may ke introduced into the mixture and these will contribute to beneficiating the steatite bodies prepared herein~
On the other hand, if the source of silica is subs-tantially pure, seperate fluxing agents are to be added to obtain a better vitrification of the steatite.
ASBESTOS TAILINGS
As far as the asbestos tailings or residues which can be used in accordance with the present inven-tion they are those normally found in most asbestosmines after removal of the as~estos fibers. In most cases ~e particle size is about -28 mesh (U.S.
standard). The asbestos tailings are then demagneti-zed in accordance with procedures well ]cnown in the art and the non-magnetic fraction is recovered.
m ough the non~magnetic fraction can be used as such, a ~etter product will be obtained if the -100 mesh fraction is recovered while grinding the -100 mesh fraction to -~00 mesh will give superior results.
The amount oE uncalcined and demagnetized fraction is used :Ln an amoun-t of from about 55 to 80 parts ky welcJh-t.
It will read:ily be appreciated ~y those s]{illed in the art that the content o:E asbestos tail-ings will vary with the mine ~here the tailings were `` ` ~L~
obtained and it is~ on the MgO and SiO2 content of the selected tailings that the amount of silica to ~e addeduwill be calculated.
SOURCE OF SILICA
As a source of silica there can obviously be used pure silica. However, a more preferred choice would be to derive the desired silica from a natural aluminum silicate since this latter material will also be useful not only in providing at least part of the silica required to bring the level of original silica in the demagnetized asbestos tailings ~.thin the percentage range required in a steatite body but also contribute to provide the necessaxy fluxing agent. If the amount of silica in the aluminum silicate ~hen added to the amount of silica in the demagne-tized asbestos tailings is not sufficient to bring the total amount oE silica to within the range of from 22 to 44.0~ then pure silica is added so as to bring the total amount of silica to within the desired range.
~s an example o:E natural aluminum sili-cates ~hich can be used in accordance with the pre-sent invention there may be mentioned: Kaolinite (Al203.2SiO2.2l120), halloysite (A1203.2SiO2.4H20), pyrophillite (Al203.4SiO2.H20), mica (Al2~(Sil.5 Al0.505)2 (0~l)2, potassium feldspath (K20.S1203.
6SiO2), sodium feldspath (Na20. Al203.6SiO2), nepheline ~L~
syenite (0.25K20~0.75Na20.1.11Al20 3 . 4.65Si02), feldspath custer (0.6 9K20 0.31Na2tÇ).1.05Al20 3 .7.05Si02), sillimanite (Al20 3 .SiO 2), spodumene (Li20.Al20 3 . 4Si02), petalite (Li20 .Al20.Al20 3 . 8Si02).
When pure silica is used the amount will vary frs:m 22 to 44.0 parts. On the other hand, when using an aluminum silicate, the amount to be added will be conditioned on the silica content of the selected aluminum silicateJ keeping in mind that the aluminum oxide in the Einal mixture as well as other elements in the silicate, should not be above 17.0%. The di~
ference l~etween the amount of silica provided by the aluminum silicate and required in the final mixture will be made up by the addition of pure silica.
The important advantage oE using natural aluminum silicates is that they constitute a source of plas ticity required to from the units. A further advantage in USinCJ those natural aluminum silicates containing sodium oxide, potassium oxide or lithium 20 oxide is that they provide a further source of fluxing agents to the mixture without the necessity of using an independent addition of said Eluxing agen ts .
FLUX NG AGENrllS
Apart from the demagnetized asl~es tos tailings, pure si.:lica and aluminum silicates, it may ke desired ~ ~#~
to add to the starting mixtu~e fluxing agents such as barium fluoride, barium oxide, calcium fluoride to make low loss steatite kodies. In a particular case ~here aluminum silicate is not used, the amount of fluxing agents could reach up to 17 parts by weigllt of the starting materials.
MIXING & COMPRESSING
The ingredients making up the mixture are then blended with a ~-etting agent or a binder to form a moist mixture. The amount of aqueous binder depends on the manufacturing process used to Eorm the desired unit. Usually the aqueous binder will ke added in an amount of from 5 to 18 parts. Aqueous binders are well known in the ceramic art and their purpose i9 to agglomerate the ingredients so that the mix can be readily handled for compression or extrusion int units. ~s an example of a suitable binder, there may be mentioned cutting oil, water, and hydrated magnesium chloride in equal parts.
Compression of the wet mixture thus obtained is carried out at a pressure of Erom ~000 to 6000 psi with a molding pressure oF 5000 psi being very satis-Eactory. The compressed units are more than suffi-ciently rigid to be handled without extra precautions.
The units may ~e stored Eor sin-tering at a later time.
.- 9 PARTICLE SIZE
The properties of the protoenstatite ceramic products obtained from the present invention can vary over a large scale depending upon the particle siæe of the starting materials. For example, the larger particles size e.g.l50 to 250 microns used will tend to give products having a fairly high water absorption accompanied with a low crushing strength. On the other hand these two features can be modified according to the type product desired by using starting materials of smaller particles size, such as those having 44 microns or less or -325 mesh U.S. Standard.
SINTERI~ ~ ER~TURE
The green compressed moulded units of the present invention are sintered within a temperature range of Erom 1250 to 1500C for a period of from
.
Steatite bodies are used primarily as high frequency insulating bodies in the electronic and electronic and electrical appliance industries and ~5 are characterized by their high dielectric strength over wide temperature ranges, low power loss in the high frequency field, a water absorption of less than one percent and a high impact or mechanical resistan-ce.
The common practice in the manufacture of steatite products consists in mixing silica-rich magnesium silicate rocks such as clinoenstatite crystals (talc) with small amounts o:E clay and a ceramic flux.
Typical steatite compositions presently available analyze as follows:
SiO2 MgO A L2 03 K2 Fe2 03 TiO2 CaONa20 BaO
% % gO % % % ~ % %
a) 64.74 28~24 4.45 1.03 0.83 0.03 0.25 0.43 --b) 61.7 29.23 2.55 0.05 1.22 0.03 0.05 0.11 5.16%
It will be seen that contrary to a), b) contains alka].ine earth oxide flux (BaO) which impro-ves dielectric properties. It will also be seen that the i.ron oxide content (Fe2O3) is relatively low in these compositions.
~64~35 It is also known that serpentine, particularly chrysotile asbestos contains the two most important constituents of steatite, namely, magnesiun oxide and silica: Appreciating the enormous amount of chrysotile asbestos tailings and residues present near every asbestos mine in the world appear highly desirable if a procedure could be found to use these tailings and residues in the manufacture of steatite compositions whereby a substantial reduction in cost would be achieved while at the same time creating a new use of these tailings and residues for which only limited use has been found. It will also be appre-ciated that asbestos fibers represent only about 5 by weight of the mined asbestos rock and thus the cost of the tailings and residues is already included in the selliny price of all asbestos fibers.
SUMMARY OF THF INVENTION
In accordance with the present invention there is provided a process for preparing proto-enstatite ceramics units which include steatite which comprises mixing uncalcined and demagnetized asbestos tai.lings with a source of silica and after compressing th:is mixture, the unit is sintered within a tempera~
ture range of from 1250 to 1500C.
The steatite ceramic units thus obtained possess many of the desirable physical characteristics of presently available steatites. More particularly the physical and electrical properties can vary extensi-vely depending on the amounts and the particule sizeof the starting materials and the sintering temperature.
DETAILED DESCRIPTION OF THE INVENTION_ Essentially, steatite falls in the proto-enstatite domain and contains the following ingre-dients as its main constituents: 2~-32% of MgO and 55-65% of SiO~, the remainder comprising aluninum oxide and ceramic fluxing agents. Ferric oxide and small amounts of other oxides may be present as impurities in the raw materials used.
It is also known that magnesium oxide, si-lica and iron oxide constitute the essential ingre-dients of asbestos tailings, the respective amounts varying ~ith the location of the mine. The following Table I illustrates the major elements in the asbestos tail:ings oE three diEferent mines TABLE I
~ine M~O SiO2 Fe2O3 OthersL.O.I.*
% ~6 %
~ ~0.80 35.~ 7.3 1.20 15.30 B 39.69 35.768.06 2.5~ 13.95 C 36.95 38.358.95 2.89 12.86 *loss on ignition It appears from Table I that asbestos tailings would not be suitable for the manufacture of steatite b~cause of their hiyh iron oxide content.
In accordance with the present invention there is provided a shaped mi~ture suitable for sinte-ring at a temperature of from 1250 to 1500C using demagnetized asbestos tailings as the essential ingre dients or, as the source of magnesium oxide and as par-tial source of silica.
More specifically, the shaped mixture compri-ses from 55 to 80 parts by weight of uncalcined and demagnetized asbestos tailings with 22 to 44.0 parts by weight of a source of silica, and from 0 to 17 parts by weight of fluxing agent. The mixture of the present inventi.on after sintering wlll provide a steatite body ~herein the percentages of MgO, SiO2 and Al203 fall within the limits prescribed for steatite compositions.
It will ~e observed that the percentage Fe2O3 content of asbestos tailings has been reduced first ~y the magnetic separation step and secondly ~y the addition of the source of silica, the latter contributing also to the reduct:ion o:E the MgO and the increase of sio2 to within the prescribed limits Eor steatite composi-tions. The remainder of the composition will be made up of the impurities normally found in demagnetized asbestos tailings.
~6~5 Furthermore, depending on the source of silica used, certain useful fluxing agents may ke introduced into the mixture and these will contribute to beneficiating the steatite bodies prepared herein~
On the other hand, if the source of silica is subs-tantially pure, seperate fluxing agents are to be added to obtain a better vitrification of the steatite.
ASBESTOS TAILINGS
As far as the asbestos tailings or residues which can be used in accordance with the present inven-tion they are those normally found in most asbestosmines after removal of the as~estos fibers. In most cases ~e particle size is about -28 mesh (U.S.
standard). The asbestos tailings are then demagneti-zed in accordance with procedures well ]cnown in the art and the non-magnetic fraction is recovered.
m ough the non~magnetic fraction can be used as such, a ~etter product will be obtained if the -100 mesh fraction is recovered while grinding the -100 mesh fraction to -~00 mesh will give superior results.
The amount oE uncalcined and demagnetized fraction is used :Ln an amoun-t of from about 55 to 80 parts ky welcJh-t.
It will read:ily be appreciated ~y those s]{illed in the art that the content o:E asbestos tail-ings will vary with the mine ~here the tailings were `` ` ~L~
obtained and it is~ on the MgO and SiO2 content of the selected tailings that the amount of silica to ~e addeduwill be calculated.
SOURCE OF SILICA
As a source of silica there can obviously be used pure silica. However, a more preferred choice would be to derive the desired silica from a natural aluminum silicate since this latter material will also be useful not only in providing at least part of the silica required to bring the level of original silica in the demagnetized asbestos tailings ~.thin the percentage range required in a steatite body but also contribute to provide the necessaxy fluxing agent. If the amount of silica in the aluminum silicate ~hen added to the amount of silica in the demagne-tized asbestos tailings is not sufficient to bring the total amount oE silica to within the range of from 22 to 44.0~ then pure silica is added so as to bring the total amount of silica to within the desired range.
~s an example o:E natural aluminum sili-cates ~hich can be used in accordance with the pre-sent invention there may be mentioned: Kaolinite (Al203.2SiO2.2l120), halloysite (A1203.2SiO2.4H20), pyrophillite (Al203.4SiO2.H20), mica (Al2~(Sil.5 Al0.505)2 (0~l)2, potassium feldspath (K20.S1203.
6SiO2), sodium feldspath (Na20. Al203.6SiO2), nepheline ~L~
syenite (0.25K20~0.75Na20.1.11Al20 3 . 4.65Si02), feldspath custer (0.6 9K20 0.31Na2tÇ).1.05Al20 3 .7.05Si02), sillimanite (Al20 3 .SiO 2), spodumene (Li20.Al20 3 . 4Si02), petalite (Li20 .Al20.Al20 3 . 8Si02).
When pure silica is used the amount will vary frs:m 22 to 44.0 parts. On the other hand, when using an aluminum silicate, the amount to be added will be conditioned on the silica content of the selected aluminum silicateJ keeping in mind that the aluminum oxide in the Einal mixture as well as other elements in the silicate, should not be above 17.0%. The di~
ference l~etween the amount of silica provided by the aluminum silicate and required in the final mixture will be made up by the addition of pure silica.
The important advantage oE using natural aluminum silicates is that they constitute a source of plas ticity required to from the units. A further advantage in USinCJ those natural aluminum silicates containing sodium oxide, potassium oxide or lithium 20 oxide is that they provide a further source of fluxing agents to the mixture without the necessity of using an independent addition of said Eluxing agen ts .
FLUX NG AGENrllS
Apart from the demagnetized asl~es tos tailings, pure si.:lica and aluminum silicates, it may ke desired ~ ~#~
to add to the starting mixtu~e fluxing agents such as barium fluoride, barium oxide, calcium fluoride to make low loss steatite kodies. In a particular case ~here aluminum silicate is not used, the amount of fluxing agents could reach up to 17 parts by weigllt of the starting materials.
MIXING & COMPRESSING
The ingredients making up the mixture are then blended with a ~-etting agent or a binder to form a moist mixture. The amount of aqueous binder depends on the manufacturing process used to Eorm the desired unit. Usually the aqueous binder will ke added in an amount of from 5 to 18 parts. Aqueous binders are well known in the ceramic art and their purpose i9 to agglomerate the ingredients so that the mix can be readily handled for compression or extrusion int units. ~s an example of a suitable binder, there may be mentioned cutting oil, water, and hydrated magnesium chloride in equal parts.
Compression of the wet mixture thus obtained is carried out at a pressure of Erom ~000 to 6000 psi with a molding pressure oF 5000 psi being very satis-Eactory. The compressed units are more than suffi-ciently rigid to be handled without extra precautions.
The units may ~e stored Eor sin-tering at a later time.
.- 9 PARTICLE SIZE
The properties of the protoenstatite ceramic products obtained from the present invention can vary over a large scale depending upon the particle siæe of the starting materials. For example, the larger particles size e.g.l50 to 250 microns used will tend to give products having a fairly high water absorption accompanied with a low crushing strength. On the other hand these two features can be modified according to the type product desired by using starting materials of smaller particles size, such as those having 44 microns or less or -325 mesh U.S. Standard.
SINTERI~ ~ ER~TURE
The green compressed moulded units of the present invention are sintered within a temperature range of Erom 1250 to 1500C for a period of from
2 to 4 hours.
STEATITE BODIES
'rhe steatite bodies obtained in accordance wlth the present invention possess the desired physical and electrical properties of known steatite compositions.
For example, they are useful as high frequency :Lnsulatinc~ materials hiyh dimensional stability, good mechanical resistance, and low dielectric loss.
(~hemically, the steatite bodies corresponding substantially to the composition of known steatite composition i.e. a MgO content of 25-32% and a Si0 2 content of from 55 to 65%. ~he balance of the composition will depend on ~hether the source of si-lica is pure silica or a mixture of aluminum silica-tes and silica. When pure silica is used the balance of the composition will comprise Fe20 3 and Al20 3 contained in the starting demagnetized asbestos tailings along with the other impurities inherent to said asbestos tailings. ~hen the source of silica is a mixture of aluminum silicate and silica the ba-lance o:E the composition will be the oxides such as E'e20 3 including those of other metals inherent in the sta:rting demagnetized asbestos tailings along with those that might ke present in the selected alumi-num silicate.
MOLDED SH:~PES
The products of the present invention are molded in the shape o~ tiles for various industrial uses. For example, ceramic tiles prepared according to the present invention can be usecl wherever an acid surEace is reclui.recl such as .Eor example laboratory table tops where the water absorption must be less than 0.5~ and floor tiles where -the water absorption must be l.ess than 3~.
~ 6~5 EXAMPLE_ The starting materials are mixed and 12 parts of a wetting agent is added to obtain a dry mixture.
The dry mixture is then imxed with a bindex and the wet mix is then compacted into units at a pressure of 5000 psi in the shape of cylinders having l l/8" in diameter and 2" in length. The green units are then dried in an oven and sintered at the indicated temperatures in each example for a period of 2 hours in an oxidizing atmosphere.
Whenever a mesh size is used in this application it is measured according to the U.S. Standard.
- 12 ~
A) FORMULATION:
59.17% demagnetized as~estos tailings (-100 mesh), (Bell Mi.nes) 27.83% silica (-200 mesh) 12.98% calcined alumina (-325 mesh) B) COMPACTING PRESSURE: (double action press): 5000 psi C) CHEMICAL COMPOSITION AFTER FIRING:
SiO 2 MgO Al20 3 Fe2 3 others 10 56.11% 25.42% 14.67% 1.93% 1.76%
D) Properties after tw~ (2) hours sintering at temperatures indicated PROPERTIES SINTERING TEMPERATURE ( C) Apparent density (g/cc) 2.8 2.27 2.52 Bulk density (g/cc) 2.15 2.18 2.01 Apparent (open) porosity (%) 23.5 4.0 20.4 Water a~sorption (~) 10. 1.84 10.11 Cold crushing stren~th (psi) 19,865 20,200 14,550 Color light grey Softening temperatures: 1325C
Sa~e operatinc~ temperature: 1300C
A) FORMULATION:
56.6% demagnetiz~dasbestos tailing -100 mesh (Bell Mines) 30.96% Kaolin -325 mesh 12.42% silica -200 mesh B) COMPACTING PRESSURE: 5000 psi C) CHEMICAL COMPOSITION AFTER FIRING:
SiO 2 MgO Al20 3 Ee2 3 others % % % % %
56.16% 25.6% 13.74% 2.02%2.37%
D) Properties after tw~ (2) hours sintering at temperatures indicated PROPERTIES SINTERING TEMPERATURE ( C) _ 1280 1300 1325 1350 Apparent density (g/cc) 2.74 2.78 2.75 fusion Bulk density (g/cc) 2.10 2.15 2.13 Apparent (open) porosity (%) 23.5 22.7 22.8 Wate:r absorption (%) 11.13 10.7 10.65 Cold crushing strength (psi) 19910 17720 16170 Color grey to ight brown Softening temperatures: 1350C
Safe operating temperature: 1325C
~_ . . .
A) FORMULATION:
61.82% demagnetized asbestos tailings-100 mesh, (Bell Mines) 13.57% silica -200 mesh 18.10% nepheline syenite -200 mesh 6.51% BaC03 B) COMPACTING PRESSURE: 5000 psi C) CEIEMICAL COMPOSITION AFTER FIRING:
SiO2 MgO Al203 Fe203 others 55.3% 27.3% 5.3% 2.07% 9.72%
D) Properties after two (2) hours sintering at temperatures indicated PROPEI~rIES SINTERING TEMPERATURE ( C) _.
Apparent density (g/cc) 1.94 2.02 fusion Bulk density (y/cc) 1.94 2.02 Apparent (open) porosity (~) 0.46 0.47 Water absorption (~) 0.23 0.23 Cold crushing strength (psi) 23,180 23,040 Color grey g.rey Softeni.ng temperatures: 1325C
Safe operatincJ temperature: 1280 - 1300C
BSERVATIONS: This composition could be a good composition for steatite bodies.
Cold crushing strength could be improved by decreasiny particle size.
This sample is identical to Example 3 except that the mix has been ground to obtain a powder going through 400 mesh.
A) FORMULATION:
61.82~ Asbestos tailings: -28 mesh demagnetized (Bell Mines) 13.57% Silica -200 mesh 18.10~ Nepheline Syenite 400 mesh 6.60% Barium carbonate All the ingredients were ball-m.illed in a porcelain jar with high alumina pebbles and water.
The resulting ship was dried and the powder obtained went through a 400 mesh.
B) COMPACTING PRESSURE: 5000 psi C) CEIEMICAL COMPOSITION AFTER FIRING:
SiO 2 MgO Al 20 3 Fe 20 3 others 55.3~ 27.3% 5.3~ 2.07% 9.72%
D) PROPERTIES AFTER TWO HOURS SINTERING AT 1315 C:
Apparent density (g/cc) 2.29 Bulk density (g/cc) 2.29 Apparent porosity % 0.02%
Water absorption % 0.01~
Cold crushing s-trength (psi) 28,505 Color Ligh-t beige SoEtening temperature -13~0C
SaEe operati.ng temperature -1300 - 1315C.
Compared to Example 3 the cold crushing strength has been .increased by about 20%, while the water absorption has been reduced tenfold.
EXAMPLE: 5 A) FORMULATION:
63.09% demagnetized asbestos tailings -100 mesh, (Carey Mines) 5.25% Kaolin -325 mesh 27.13-r'6 silica -200 mesh 4.52% alumina -325 mesh B) COMPACTING PRESSURE: 5000 psi C) CHEMICAL COMPOSITION AFTER FIRING:
SiO2 MgO Al~03 Fe203 others 58.76% 30.69% 7.6% 1.96% 0.89%
D) Properties after two (2) hours sintering at temperatures indicated PROPERTIES SINTERIN.G TEMPERATURE ( C) -Apparent densi-ty (g/cc) 2.85 2.65 2.27 2.18 Bulk density (g/cc) 1.88 2.15 2~23 2.14 Apparent (open) porosity (r~) 34.119.1 2.12 2.05 Water absorption (%)18.0 8.8 0.9 0.9 Cold crushing strength (psi) 12,820 22,320 30,050 33,850 Color light grey Softening temperatures: 1~50C
Safe operating. temperature: 1425 ~ 1~50C
BSERV~TIONS: This composition could be a good candidate for steatite bodies when sintered at 1425 -1450 C. Cold c:rushing strength could be improved by decreasing particle size.
~31L~
-A) FORMULATION:
56.61% Asbestos tailings -100 mesh, demagnetized (Carey) 522.4% feldspath custer -325 mesh 9.a5% silica -200 mesh 5.4% betonite -325 mesh 5.74% BaC03 B) COMPACTING PRESSURE: 5000 psi C) CHEMICAL COMPOSITION AFTER FIRING:
SiO2 MgO Al203 Fe203 others % % % % %
55.92% 28.25% 5.68% 1.94%8.21%
D) Properties aEter two (2) hours SinterinCJ at 15temperatures indicated PROPERTIES SINTERING TEMPERATURE (C) ~ . ..................... ... ~
Apparent density (g/cc) 2.2 2.08 2.45 Bulk density (g/cc) 2.11 2.03 1.93 Apparent (open) porosity (%) 4.03 2.91 21.36 Wa-ter absorption-(%) 1.90 1.40 11.0 Cold crushlng strength (psi) 24440 15880 6680 Color li~ht light light grey grey ~rey SoEtening -temperatures: 1325C
Sa.Ee operatincJ -temperatures: 1280-1300C
~___ _ ___ A) FOE~ULATION:
72.6% Residus -400 mesh (Bell Mines) 27.4% silica -400 mesh B) COMPACTING PRESSURE: 5000 psi C) CEIEMICAI. COMPOSITION AFTER FIRING:
SiO2 MgO Al203 Fe203 others 62.~8% 31.78% 0.81% 2.40% 2.11%
D) PROPERTIES AFTER 4 HOURS SINTERING AT 1325 C
Apparent density (g/cc) 2.63 Bulk density (g/cc) 2.61 Apparent porosity (%) 0~84 Water absorption (%) n . 32 Cold crushing s-trength (psi) 27,190 Color dark beige Softening tempera-ture 1350C
Safe operating temperature 1310 - 1330C
STEATITE BODIES
'rhe steatite bodies obtained in accordance wlth the present invention possess the desired physical and electrical properties of known steatite compositions.
For example, they are useful as high frequency :Lnsulatinc~ materials hiyh dimensional stability, good mechanical resistance, and low dielectric loss.
(~hemically, the steatite bodies corresponding substantially to the composition of known steatite composition i.e. a MgO content of 25-32% and a Si0 2 content of from 55 to 65%. ~he balance of the composition will depend on ~hether the source of si-lica is pure silica or a mixture of aluminum silica-tes and silica. When pure silica is used the balance of the composition will comprise Fe20 3 and Al20 3 contained in the starting demagnetized asbestos tailings along with the other impurities inherent to said asbestos tailings. ~hen the source of silica is a mixture of aluminum silicate and silica the ba-lance o:E the composition will be the oxides such as E'e20 3 including those of other metals inherent in the sta:rting demagnetized asbestos tailings along with those that might ke present in the selected alumi-num silicate.
MOLDED SH:~PES
The products of the present invention are molded in the shape o~ tiles for various industrial uses. For example, ceramic tiles prepared according to the present invention can be usecl wherever an acid surEace is reclui.recl such as .Eor example laboratory table tops where the water absorption must be less than 0.5~ and floor tiles where -the water absorption must be l.ess than 3~.
~ 6~5 EXAMPLE_ The starting materials are mixed and 12 parts of a wetting agent is added to obtain a dry mixture.
The dry mixture is then imxed with a bindex and the wet mix is then compacted into units at a pressure of 5000 psi in the shape of cylinders having l l/8" in diameter and 2" in length. The green units are then dried in an oven and sintered at the indicated temperatures in each example for a period of 2 hours in an oxidizing atmosphere.
Whenever a mesh size is used in this application it is measured according to the U.S. Standard.
- 12 ~
A) FORMULATION:
59.17% demagnetized as~estos tailings (-100 mesh), (Bell Mi.nes) 27.83% silica (-200 mesh) 12.98% calcined alumina (-325 mesh) B) COMPACTING PRESSURE: (double action press): 5000 psi C) CHEMICAL COMPOSITION AFTER FIRING:
SiO 2 MgO Al20 3 Fe2 3 others 10 56.11% 25.42% 14.67% 1.93% 1.76%
D) Properties after tw~ (2) hours sintering at temperatures indicated PROPERTIES SINTERING TEMPERATURE ( C) Apparent density (g/cc) 2.8 2.27 2.52 Bulk density (g/cc) 2.15 2.18 2.01 Apparent (open) porosity (%) 23.5 4.0 20.4 Water a~sorption (~) 10. 1.84 10.11 Cold crushing stren~th (psi) 19,865 20,200 14,550 Color light grey Softening temperatures: 1325C
Sa~e operatinc~ temperature: 1300C
A) FORMULATION:
56.6% demagnetiz~dasbestos tailing -100 mesh (Bell Mines) 30.96% Kaolin -325 mesh 12.42% silica -200 mesh B) COMPACTING PRESSURE: 5000 psi C) CHEMICAL COMPOSITION AFTER FIRING:
SiO 2 MgO Al20 3 Ee2 3 others % % % % %
56.16% 25.6% 13.74% 2.02%2.37%
D) Properties after tw~ (2) hours sintering at temperatures indicated PROPERTIES SINTERING TEMPERATURE ( C) _ 1280 1300 1325 1350 Apparent density (g/cc) 2.74 2.78 2.75 fusion Bulk density (g/cc) 2.10 2.15 2.13 Apparent (open) porosity (%) 23.5 22.7 22.8 Wate:r absorption (%) 11.13 10.7 10.65 Cold crushing strength (psi) 19910 17720 16170 Color grey to ight brown Softening temperatures: 1350C
Safe operating temperature: 1325C
~_ . . .
A) FORMULATION:
61.82% demagnetized asbestos tailings-100 mesh, (Bell Mines) 13.57% silica -200 mesh 18.10% nepheline syenite -200 mesh 6.51% BaC03 B) COMPACTING PRESSURE: 5000 psi C) CEIEMICAL COMPOSITION AFTER FIRING:
SiO2 MgO Al203 Fe203 others 55.3% 27.3% 5.3% 2.07% 9.72%
D) Properties after two (2) hours sintering at temperatures indicated PROPEI~rIES SINTERING TEMPERATURE ( C) _.
Apparent density (g/cc) 1.94 2.02 fusion Bulk density (y/cc) 1.94 2.02 Apparent (open) porosity (~) 0.46 0.47 Water absorption (~) 0.23 0.23 Cold crushing strength (psi) 23,180 23,040 Color grey g.rey Softeni.ng temperatures: 1325C
Safe operatincJ temperature: 1280 - 1300C
BSERVATIONS: This composition could be a good composition for steatite bodies.
Cold crushing strength could be improved by decreasiny particle size.
This sample is identical to Example 3 except that the mix has been ground to obtain a powder going through 400 mesh.
A) FORMULATION:
61.82~ Asbestos tailings: -28 mesh demagnetized (Bell Mines) 13.57% Silica -200 mesh 18.10~ Nepheline Syenite 400 mesh 6.60% Barium carbonate All the ingredients were ball-m.illed in a porcelain jar with high alumina pebbles and water.
The resulting ship was dried and the powder obtained went through a 400 mesh.
B) COMPACTING PRESSURE: 5000 psi C) CEIEMICAL COMPOSITION AFTER FIRING:
SiO 2 MgO Al 20 3 Fe 20 3 others 55.3~ 27.3% 5.3~ 2.07% 9.72%
D) PROPERTIES AFTER TWO HOURS SINTERING AT 1315 C:
Apparent density (g/cc) 2.29 Bulk density (g/cc) 2.29 Apparent porosity % 0.02%
Water absorption % 0.01~
Cold crushing s-trength (psi) 28,505 Color Ligh-t beige SoEtening temperature -13~0C
SaEe operati.ng temperature -1300 - 1315C.
Compared to Example 3 the cold crushing strength has been .increased by about 20%, while the water absorption has been reduced tenfold.
EXAMPLE: 5 A) FORMULATION:
63.09% demagnetized asbestos tailings -100 mesh, (Carey Mines) 5.25% Kaolin -325 mesh 27.13-r'6 silica -200 mesh 4.52% alumina -325 mesh B) COMPACTING PRESSURE: 5000 psi C) CHEMICAL COMPOSITION AFTER FIRING:
SiO2 MgO Al~03 Fe203 others 58.76% 30.69% 7.6% 1.96% 0.89%
D) Properties after two (2) hours sintering at temperatures indicated PROPERTIES SINTERIN.G TEMPERATURE ( C) -Apparent densi-ty (g/cc) 2.85 2.65 2.27 2.18 Bulk density (g/cc) 1.88 2.15 2~23 2.14 Apparent (open) porosity (r~) 34.119.1 2.12 2.05 Water absorption (%)18.0 8.8 0.9 0.9 Cold crushing strength (psi) 12,820 22,320 30,050 33,850 Color light grey Softening temperatures: 1~50C
Safe operating. temperature: 1425 ~ 1~50C
BSERV~TIONS: This composition could be a good candidate for steatite bodies when sintered at 1425 -1450 C. Cold c:rushing strength could be improved by decreasing particle size.
~31L~
-A) FORMULATION:
56.61% Asbestos tailings -100 mesh, demagnetized (Carey) 522.4% feldspath custer -325 mesh 9.a5% silica -200 mesh 5.4% betonite -325 mesh 5.74% BaC03 B) COMPACTING PRESSURE: 5000 psi C) CHEMICAL COMPOSITION AFTER FIRING:
SiO2 MgO Al203 Fe203 others % % % % %
55.92% 28.25% 5.68% 1.94%8.21%
D) Properties aEter two (2) hours SinterinCJ at 15temperatures indicated PROPERTIES SINTERING TEMPERATURE (C) ~ . ..................... ... ~
Apparent density (g/cc) 2.2 2.08 2.45 Bulk density (g/cc) 2.11 2.03 1.93 Apparent (open) porosity (%) 4.03 2.91 21.36 Wa-ter absorption-(%) 1.90 1.40 11.0 Cold crushlng strength (psi) 24440 15880 6680 Color li~ht light light grey grey ~rey SoEtening -temperatures: 1325C
Sa.Ee operatincJ -temperatures: 1280-1300C
~___ _ ___ A) FOE~ULATION:
72.6% Residus -400 mesh (Bell Mines) 27.4% silica -400 mesh B) COMPACTING PRESSURE: 5000 psi C) CEIEMICAI. COMPOSITION AFTER FIRING:
SiO2 MgO Al203 Fe203 others 62.~8% 31.78% 0.81% 2.40% 2.11%
D) PROPERTIES AFTER 4 HOURS SINTERING AT 1325 C
Apparent density (g/cc) 2.63 Bulk density (g/cc) 2.61 Apparent porosity (%) 0~84 Water absorption (%) n . 32 Cold crushing s-trength (psi) 27,190 Color dark beige Softening tempera-ture 1350C
Safe operating temperature 1310 - 1330C
Claims (8)
1. A process for the preparation of proto-enstatite ceramic units which comprises:
a) mixing 55 to 80 parts by weight of un-calcined demagnetized asbestos tailings with 22 to 44.0 parts by weight of a source of silica selected from the group consisting of (a) natural aluminum silicate and (b) a substantially pure silica and mixtures of (a) and (b), and from 0 to 17 parts of fluxing agents;
b) compressing or extruding the said mixture into units;
c) firing said units at a temperature of from 1250 to 1500°C, and, d) recovering protoenstatite ceramic units having as main constituents a MgO content of from 25 to 32% by weight and a SiO2 content of from 55 to 65% by weight.
a) mixing 55 to 80 parts by weight of un-calcined demagnetized asbestos tailings with 22 to 44.0 parts by weight of a source of silica selected from the group consisting of (a) natural aluminum silicate and (b) a substantially pure silica and mixtures of (a) and (b), and from 0 to 17 parts of fluxing agents;
b) compressing or extruding the said mixture into units;
c) firing said units at a temperature of from 1250 to 1500°C, and, d) recovering protoenstatite ceramic units having as main constituents a MgO content of from 25 to 32% by weight and a SiO2 content of from 55 to 65% by weight.
2. The process of Claim 1, wherein the source of silica is substantially pure silica.
3. The process of Claim 1, wherein the source of silica is made up of silica contained in a natural aluminum silicate and a substantially pure silica, the total amount of the thus supplied silica being from 22 to 44.0 parts by weight and the protoenstatite ceramic units thus obtained contain from 25 to 32% by weight of MgO, 55 to 65% by weight of SiO2, the balance comprising the oxides of other metals present in the asbestos tailings and in the selected aluminum silicate.
4. The process of Claim 1, 2 or 3, wherein the mixture of step (a) contains up to 17 parts by weight of at least one fluxing agent.
5. The process of Claim 1 or 2, wherein the mixture of step (a) contains up to 17 parts by weight of substantially pure alumina.
6. The process of Claim 1, wherein the source of silica is a natural aluminum silicate.
7. The process of Claim 6, wherein the natu-ral aluminum silicate is kaolinite, halloysite, pyro-phillite, mica, potassium feldspath, sodium feldspath, nepheline syenite, feldspath custer, sillimamite, spodu-mine, or petalite.
8. The process of Claim 1, wherein the natu-ral aluminum silicate is kaolinite, halloysite, pyro-phillite, mica, potassium feldspath, sodium feldspath, nepheline syenite, feldspath custer, sillimamite, spodu-mine, or petalite.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000410353A CA1196485A (en) | 1982-08-27 | 1982-08-27 | Protoenstatite ceramic units and process for their preparation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000410353A CA1196485A (en) | 1982-08-27 | 1982-08-27 | Protoenstatite ceramic units and process for their preparation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1196485A true CA1196485A (en) | 1985-11-12 |
Family
ID=4123495
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000410353A Expired CA1196485A (en) | 1982-08-27 | 1982-08-27 | Protoenstatite ceramic units and process for their preparation |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1196485A (en) |
-
1982
- 1982-08-27 CA CA000410353A patent/CA1196485A/en not_active Expired
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