AUSTRALIA PATENTS ACT 1990 REGULATION 3 2 Nane of Applicant: SAINT-GOBAIN CERAMICS & PLASTICS, INC. Actual Inventor/s: Tihana Fuss; Laurie San-Miguel; Kevin R. Dickson; and Walter T. Stephens. Address for Service: F. F. WELLINGTON & CO_ Patent and Trade Mark Attorneys, 312 St. Kilda Road, Melboume, Southbank, Victoria, 3006. Invention Title: "CERAMIC ARTICLE AND PROCESS FOR MAKING THE SAME" Details of Associated Provisional Applications Nos: The following statement is a fil description of this invention including the best method of perfonning it known to us, CROSSREFERENCE TO RELATED APPLICATIONS This applicadon is a 'divisional application derived front Australiar Patent Application No 2009334496 (PCT/US200/069965: WO 2010/078524), claiming priority of US App ication No. 61/141]890. the entire text of which are hereby incorporated herein by reference. BACKGROUND OF THE INVENTION Ceramic particles are produced for use in a wide vadety of industrial application Some OfNhee= p i include uing a plurality of ceramic particles: as a proppant to facilitate the removal of liquids and/or gases from wells that have been drilled into geological formations; as a media for scouring, grinding or polishing; as a bed support media in a chemical reactor as a heat transfer media; as a filtration media; and as roofing granules when applied to asphalt shingles. Examples of patents that disclose ceramic particles and methods of manufacturing the same include US 4,632,876, US 7036,59i and CA I217319, SUMMARY Embodiments of the present invention provide methods of producing ceramic particles that establish and maintain porosiuthroughout the particle manufacturing process. The process of these embodiments provides an alterative to processes that use significant quantities of pore forming materials which must be removed from the particle during the manufacturing process. Other embodiments of the sent invention provide ceramic articles with a payur m tnd crysalline phase. In one embodiment this invention is a process for producing ceramic particles which may include the following steps. Forming a particle precursor comprisng more than 5 weightpercentbut less than 30 weight percent of a first ceramic material and at least 40 weight percent of a second ceramic material. The ceramic materials are substantially uniformly distributed within the precursor. Heating the precursor to a mnaxinmn 2 temperature above the sintering temperature of thefirst ceramic material and below the sperature of the second ceramic material. The ceamic particle has at least 16 percent total porosity. i another embodiment, this invention is a ceramic article comprising a chemical composition comprising AlfO and Si.) wherein the ratio of the weight percent of Ab 3 to Ab) and SI, as determined by XRF analysis, is less than 032; and at least iweigt percent of the article is an alumina crystalline phase, as determined by XRD analysis using an internal standard. BRIEF DESCRIPmON OF THE DRAWINGS fig, 1 is a process flow chart according to one embodiment; and Fig 2 is a dilatometry curve. DETAILED DESCRIPTION As used herein die phrase "crush resistance' Tefers to the particle's ability to withstand crushing. Crush resistance is commonly used to denote the strength of a proppant and nay be determined using ISO 13503-2.2006(E) A strong proppant generates a lower weight percent crush resistance than a weak proppant at the same closure stress. For example, a proppant that has a 2 weight percent crush resistance considered to be a strong proppa and is preferred to a weak that has a 10 weit percent crush resistance. As used herein, the phrase cemic particle's total porosity" refers to the sum of the particles open porosity and closed porosity. The ceramic particle's total porosity closed porosity and open porosity may be determined as will be described below As used herein, the phrase 'alumina crystalline phase" includes any crystalline phase that contains an ordered array of aluminum and oxygen atoms and specifically includes crystalline phases commonly identified, fr example, as alpha-aluminatheta alunina, delta-alunina, gamma-alumina, cii -aluminia and kapp-aluamina, Common names for some of the alumina crystalline phases may also be used herein. For example. alpha alumina may also be identified herein as corundum.
As used herein references to chemical content of a ceramic article refer to the weigh, percent component of thA measured chemical. Processes for manufacturing ceramic parties have been devised and used for many years to manufacture large quantities of ceramic particles such as proppants, Because proppants are used in a wide variety of geoiogical formations at different depths and exposed to extremes in temperature and pressurethe physical characteristics of the proppants may need to be customized in order to optie the performance of the proppant in a particular environment. Some of the properties which may impact the performance of the proppant include specific gravity, porosity, crush strength and conductivity. Changing one physical property may inherently change one of more of the other properties in an undesirable nranner Consequently, significant effort has been made to develop presses that alter the properties that are important in one application while simultaneously minimizrng undesirable changes to the particle's other properties, Furthermore proppant manufacturers have tried to reduce the cost of manufacturing proppants by eliminatin materiials and/or process steps without compromising the performance of the proppant. With regard to producing a proppant having a desired specific gravity, some processes have relied upon the use of pore forming materials to create porosity vithin the proppant. wo common classes of pore fonrers are known as either transiener insitu. Transient pore farmers may be reioved from the proppant by a thermal or chemical process which results in the creation of a pore or pores approximatdy equal in volme to the material that was removed. Examples of transient pore farmers include nut shells, synthetic organic material, sawdustad cereal waste. In contrast, 'n-situ pore orers typically expand upon heating and create a pore that is significantly larger than the volume occupied by the pore former prior to heating. An example of an in-situ pore former is siicon carbide The pores created by the pore tormers may be open pores and/or closed pores. One problem with using pore forniers is that they add to the cost of production because the pore former must be purchased, mixedwith the other ingredients used to make the proppant arId then energy and/ornimerials must be used to remove the pore former in some processes, the removal of pore coming materials results in the generation of solid or gaseous by-products which ma' cause environmental problems that must be addressed and increases the cost of the manufacturing pcss. Furthermore, the use of pore formers may -4create variability within the proppant manufacturing process because the steps used to incorporate and remove the pore forming material m"ay include hight differences in mxing procedures. haig temperatures, etc. Whie a change in the temperature at which the proppant is heated may appear to be relatively snaI1 the change n temperature may cause a significant change in the volume of gas generated by an in-situ pore former which would result in a larger pore than would be created at a slightly lower temperature. Embodiments of the present invention address somc of the problems described above by selecting materials and processing steps that enable the proppant manufacturer to produc a particle precursor that has approximately the desired porosity incorporated into the parties precursor and this porosity is retained in the proppant. Pore farmers are not required to generate porosity. Shown in Fig I is a process flow chart of an embodiment tht includes the following steps. Step 20 includes providing a mixture that inchides a first ceramic material and a second ceramic material wherein the sintering temperature of the first ceramic material is less than the sintering temperature of the second ceramic material Optionally, the mixture may include other materials such as binders and solvents Suitable solvents include water and soni alcohols. A binder may be one or more materials selected from organe starches such as drilling starch, as well as gumns or resins that are sold commercially for such purposes A. binder may also be an inorganic nateial such as dly or an acid. Binders are usually added in an amount less than 10 weight percent of the mixture and may be added dr or as a solution. While a binder may be responsble for some level of porosity in a. ceranic particle, hinders areot considered pore formers herein The composition of the mixture may be limited to less than 0. weight percent of one or more pore 'rmiers selected from the ist consisting of a transient pore former, an in-situ pore former, and combinations thereof Transient pore frm'ers may be limited to eiss than 0.05 weight percent of the mixture. Insitu pore former may be limited to less than 01 weight percent of the mixture. In one embodiment, the mixture will not include any pore farmers. Step 22 includes forming a particle precursor which is defined herein as a particle wherein the first and second ceramic materials are substantialy uniformly distributed therethrough and solvents, such as water have been removed so that the precursors loss on drying (LOD) after heating to between 11 f"C and 130"C for two hours is less than one percent of the precursor's s g The precursor may or may not contain optional of hepecror tatngwi Alt inredients such as a binder. The precursor may inchide weight percent to 30 weight percent of the first ceramic material and at least40 weight percent of the second ceramic material. in some embodiments, the precursor may include between 10 weight percent and 20 weight percent of the firstceramic material. In step 24, the precursor is heated to a maxim m temperature which is above the sintering temperature of the firsteramic material and below the sintering temperature of the second ceramic material. In some embodiments, the precursor may be heated to a maximum temperature which is above the melting temperature of the first ceramic material which is higher than the sintering temperature of the first canic material. During the heating step, if the temperature exceeds the melig temperature of the first ceramic material, the first ceramic material may convert from a solid material to a flIowale material and may flow over the second ceramic material hi step 26.the particle precursor is cooled to ambient temperature thereby forming a ceramic panicle With regard to step 20, both the first and second ceramic materials may be provided as powders which include a plurality ofgannles In particular embodiments granules may range from I to 10 microns miore specificalny from 6 to 8 microns, The first and second ceramic materials may be selected so that the sintering temperatureof the first eramic material is lower than the melting temperature of the first ceramic material and both are lower than the sinterim temperature of the second ceramic material While the exact difference between the melting temperature of the first ceramic material and the sintering temperature of the second ceramic material iay not be critical, a difference of 50"C may be workable in particular embodiments. For example, a suitable first ceramic material may he selected from the group consisting of feldspar and nepheline syuite, which has a melting temperature of approximately I (1* and combinations thereof A suitable second ceramic material may be selected from the group consisting of claymagnesia alumina and bauxite, wich has a sintering temperature of approximately I450C, and combinations thereof With regard to step 22 forming a particle precursornay be achieved by processing the mixture through a machine such as an ich R02 mixer, which is available front American Process Systems, unch Machines Inc. o1rney USA, thereby forming at least a portion of the mixture into a large mnber of small granules which maybe referred to as greenware. If the granues contain optional ingredients; such as solvents and binders, -6the optional ingredients may he removed by dring the granules iII an oven to a sufficiently high temperature, such as 200C or higher, to drive the optional ingredients ftmmr the graui n If desired,,5, thaarceircrosda.epoese hoghasre apparatns that includes a No&8 ASTM sieve designationwhich has 236 mu apertures and a No. 70 ASTM sieve designation which has 212 pm. sieve apertures. The precursors selected for heating in step 24 may flow through the No. S sieve and not flow through the No. 70 sieve. hi step 24, the precursor is heated to a maximum temperature which is above the sintering temperature, and perhaps above the melting temperature, of the first ceramic material and belov the sintering temperature ofthe second cenmic materia. Conseq uently, thew maxiumII' temnperature of thle, heaig seisesthnthsiern temperature of the second ceranie materiaL n particular embodimentsthe maximum temperature of the heating step is at least 25C less than the sintermi temperature of the second ceramic material As used herein a ceramic materials melting temperature is the temperature at Which the ceramic material begins to soften and become flowahle. F lowability of the first ceramnic material at a temperature that is lower than the sintering temperature of the second ceramic material may allow the irsi ceramic internal to at least partially flow onto the second ceramic mateia Contact between the first and second ceramic materials during the heating step may allow the creation of bonds between the granules of the first and second ceramic. A ceramic material's statering temperature may be determined by creating a plot of di latoretry data and identifying the temperature which corresponds to the midpoint of the ure. For example,shown in Fig 2 isat exemplary graph of a dilatometry curve where the percent of linear change (PLK C) is plotted versus temperature a hypothetical ceramic mateial that could be used to form a proppant. The percent of linear change may be determined using dilatometry: A commercially available dilatometer is an Anter nodel remnsssea changed as the temperature of the material is increased. The second region f the sintering profile is defined by a is temperature 4 t hitl the maueial stlsto shihnk and a second temperature 36 at which the shrinkage termihnates. The third region 38 of the sintering profie begins at temperature 36 and represents the region where material no longer shrinks despite further increases the material temperature.
Temperature 34 indicates the start of shrinkage and temperatureindicates the termination of shrinkage. Temperature 40 represents the material's nominal sintering temperature which may be determined by identying the point on the curve where the material has achieved 50% of the amount of shrinkage disclosed by the curve and then determining the temperature at which the 50% shrinkage was achieved. The total amount of shrinkage 42 is represented by the difference between the value of the starting linear dimension 44 aid the value of the final linear dimension 46 In step 26 the particles of the first ceramic material and the second ceram material are cooled to ambient temperature which is defined herein as any temperature between 20C and 30 C thereby forming a bonded, ceramic particle. The total weight of the first and second ceramic materials may represent at least 85 weight percent, more preferably 90 weight of the ceramic ic i th heating step he first ceramic material may form a glass phase The materials and processing conditions are selected so that the ceramic particles weight may be within eight percent of the precursor's weight In some embodimentsthe ceramic particle's weight may be wihin four weight percent even within two weight percent, of the precursor's wei gh If desired, the ceramic particles may be processed through a screening apparatus that includes a first screen, which eliminates particles having a diameter larger than the first screen's opening, and a second screen. which eliminates particles having a diameter smaller tan the second screen's opening. A suitablefrst screen is a No.8 ASTM sieve, which has 236 mm openings, and a suitable second screen is a No. ~0 ASITM. sieve which has 212 pm openings. The ceramic particles selected for use as a proppant may flow through the No, 8 sieve and not flow through the No 70 sieve, Ceramic articles, such as proppants, made by a process according to embodiments of this invention experience very little densification during the heating and bonding steps because there are no or very little pore farmers incorporated into the precursor and the maximum heatinng temperature does not exceed the sinter temperature of the second ceramic material Due to the lack of densification, the amount of porosity that is inherently incorporated in the precursor during the forning step may remain substantially the same as the amount of porosity in the ceramic particle afte the formation of the ceramic particle. The ceramic particle's total porosity may be at least 2 percent, 5 percent, 10 percent or even 15 percent of the ceramic particle's total volume. The particle's closed porosity may represent more than 70 percent, 75 percent or 80 percei of the total porosity, The particle's open porosity may represent less than 20 percent. 15 percent or even 10 percent of the total porosity. intermediate values such as: 82 percent closed porosity and 18 percent open porosity; or 88 percent closed porosity and 12 percent open porosity are also fiasible A particle's total porosity, open porosity and closed porosity may be determined as follows. Begin by using a CEO pycnornieter. which uses a fine powder to measure the particle's apparent specific gravity (PtO). The fine powder effectively encapsulates the particle anid does not penetrate the particle's open or closed pores. Next, measure the particle's apparent specific gravity (p using a helium pyconeter wherein the helium penetrates the partic les open pores. Next, determine the true density p ) of the ceramic particle by grading the particle such that the ground particles flow through a 60 mesh screen and then use helium pycnometry to determine the volume of the ground particles. The total porosity (P 0 1 closed porosity im and open porosity ( may then be calculated using the following formulas: Total porosity (opened + closed) . Opened poslrIY EXAMPLES Three lots of proppants, designated herein as Lot A, Lot B and Lot C, were made as follows. Lot A represents ceramic particles made by a conventional process and sintered at 1250"C, Lot B represents ceramic particles made by the same conventional process as Lot A but sintered at 1450C. Lot Ci represents ceramic particles made by an embodiment of a process of this invention. Shown in Table 1 are the lots' raw materials, sinterng temperatures, crush data and porosity data. ,9-.
Table I Lot A Lot BotC *(Coxnpariim) comparess) int Main Charge-------------- .... AlphaAlumna____ ___ 55S a 5455 8020 weight percent mixture lphalnia and npeine 5455 a alph)"a alm nphel -bll Drilling starch 108.9 g 108 9 g 1089 9 water 1145 6l465 - 45 6 Dust In................ Xlgha Alumina 1364 g 6 4 g_ ---- 2( weight percent mixture of alpha almina and nephline g -- _ _ ---- -1 -- ------ .... .- ----- Sinterin ilem rture 1250C 1450 C 12500C ---- ---- ----....... .......................... Average crush at 5L MPa (7,500 psi) 14.4% 22% j 18-1 Total _ ___ ot - 18% 10% 12 4% Lot A was manufactured by combining 5,455 grams of alpha alumina with 1089 g of drilling starch. The dry ingredients were disposed into an Pinch R02 mixer with both the pan and rotorng, The rotor speed was set at 80 percent of maximum speed. A fter 30 seconds, the water was poured into the mixer directly onto the rotating dry ingredients, Approximately 30 seconds was used to distribute the water thereby producing a moistened mixture. The moistened mixture, which may be referred to herein as the "main charge" was allowed to rotate for three minutes during which time a pharality of spheres were formed. The rotor speed was then reduced to minimum speed as the pan continued to rotate. Next, the 1,364 g of alpha alumina, which may be described as the "dust in" charge, was then added slowly to the rotating spheres, The slow addition of the dust in charge took. approximately three minutes and may be described herein as "dusting in" the alpha alumina. After completing the dusting in of the alpha alumina, the pan continued to rotate for approximately 20 seconds. The formed spheres of alpha alumina, binder and water, were removed from the mixer, dried overnight and sintered in a rotating kiln at 1250*(7 for two hours. -10- The ceramic particles in Lot B were manufactured exactly the same as the particles in Lot A except that the particle precursors were sintered at 450C [he ceramic partcles i ot CWere nianufCtured using an 8020 Weight ratio of alpha alumina and nepheline syenite, respectively as both the main charge and the dust in charge, All other ingredients and processing conditions were the same as used to make the precursors in Lots A and B. The particle precursors in Lot C were sintered at 125( 0 C which is above the melting point of the nepheline syenite and below the sintering temperature of the alpha alumina After sinter-ing, all lots wvere screencd to -a common particle size distribution. Crush resistance, total porosity and closed porosity Were determined as desCribed above. The data shows that the ceramic particles of Lot A had adequate total porosity (17.) but the crush resistance ai 51.7 lPa was 14.4% which may be undesirable for use n commercial operations. Lot B had very good crush resistance (2,2%) but the total porosity% was well below the desired 10% total porosity In contrast, Lot C,which represents ceramic patils ae yan emibodimlent of a -roes of this in,,enionu, had acceptable crush resistance (8. ) and acceptable total porosiy 12%. Furthermore, only Lot C had total porosity and closed porosity both greater than10% Embodiments of this invention may have Crush resistance le-ss than~ 15 at 1 I.Pa. (7,500 psi) and tLotal -porosity greater than 10%. An embodiment of a process of this invention may bec used to berate ceramic articles, including proppant particles which have a particular combination of chemistry and alumina crystalline phase According to the phase diagram for an A1 2 0 2 and SO binary system ifthe weight ration" ol to the total of Al0; and SiO, is greawh tha07 the article should exhibit an alumina crystalline structure. Conversely, if the ratio of m1 2 0 3 to the total of Al23 and. SiO is less than 0,72, the articlc should not exhibit an alumnina crystalline structure, Contrary to this teachmg; ceramic articles of this mvention may have a ratio of AUlh to the total of A60, and SiC) less than 2.72 and at the same time, at least a portion of the article has an alumina crystalne phase structure In some embodimentsthe alumina crystalline phase may be greater than 5 percentJ percent or even 20 percent by weighdit as determined by XRF analysis and the natio of Al)O toe te total of AIXo and Si02 may be less than 0.65. 0.55 or even 0.45With particular reference to proppants an alumina crystalline phase structure is desirable because the ahmina ciystalline phase
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improves the proppant' s crush strength. This particular combination of chemistry and phase may be produced using an embodiment of a process of this invention. Furthermore, as will be illustrated and described belo calciann the second cerainc material prior to fornin g the mixture used to make the ardcle can also be used in combination with the previously described process to produce a ceramic article having the particular relationship between chemistry and alumina crystalline phase. To Vilustrate the impact that adding the first ceranic material to the second ceramic material has on the ratio of the weight percent of A10 4 o A1 3 and SiO two lots, designated herein as Lot D and Lot E were prepared and manufactured io disc shaped articles. Lot D was manueatured using a bauxite ore that had been milled to attain a dt particle size of approximately~pm S A known quantity of the milled bauxite ore was mixed With a solvent O weight perentwater and a hinder i weight percent of a polyvinyl alcohol (PVA) solution (20 % concentration) A 65 g quantity of the mixture was disposed into a circular die cavity that measured approximately 32 m in diameter A circular plate secured to a press was then used to compress the mixture in the cavity to approximately 345 MPa (5000 psi) thereby generating a disc that measured approximately 32 mniin diameter. Lot E was manufctured using an 80:20 mixture of bauxite ore and nepheline syenite. Prior to mixing ith the 10 weight percent water and 1 eight percentP A both the ore and nepheline syenite were separately milled to attain a d 5 particle size of approximately 8 ti A disc as formed of the mixture in lot Euing the sanme process used to make the disc in lot D. Al of the discs were then heated to 1250C for two hours. An x-ray fhorescent (XRF) analytical apparatuswas then used to determine the ratio of the weight percent of AL0 3 to Alit and SiOt An xray diffraction (XRD) analytical apparatus using Si powder as an internal standard was used to determine the phases of each disc. Shown below inTable 2 are the XRF and XRD analytical resuls for Lots D and E Table 2 XRF 0771 0 658 \XRD 24% corundum 38% corundum ratio of the weight percent of A1 2 3 to the totaloo AoIf and SiOt -12- The data supports the conclusion that Lot F. which ichided the addition of nephdine se.nite relative to Lot D, had a 658 ratio of the weight percent of AlIOft V Al~z and SiQwhich was lower than 071 ratio of the weight percent f A0to AlO 3 and SiO found in I ot D; A the same i e, ot ;had 38 percent corundum which was higher than the 24 percent corundum in Lot D, To demonstrate the impact of calcining the second ceramic material this embodiment on the (T) article'sratio of the weight percent of Al 2 -Oto AbC 3 aand SiC) 2 and (2) the alumina crystalline phase two lots, designated herein as Lot F and Lot Gwere prepared and manufactured into disc shaped components LotFvas manufactured using bauxite ore thaut had ben Calcined betWeen S0Y and atleast 900*C in an industrial calciner por to milling the ore to a particle suM having a d8 of approxmatelIm The milled calcined ore was then mixed with 10 weight percent water and I weight percent WA. Discs of the mixture from lot F were mmutactured sing the same process as described above with reference to lots P anda. The discs from lots f) and E were then heated to 1 250* for two hours. Calcining the ore to a temperature greater than 800 C which may be referred to herein as ovencalcing was intended to increase the ore's alumina crystalline content and also remove organic compounds as indicated by a reductionin the orems Loss on Ignition (L-OT). InS ome embodiments, the alumina crystalline content of the over ealcined ore may be at 5 percent, 10weight percent or even 2F weigt percent The ore's LI may be less than3weight percent 2 weight percent or even I weight percent Ore with a ower O is less reactive than ore with a hig her LOI. The over calcined ore's alumina crystalline content and )l may be controlled by controlling the time and temperature of the over calcination process. tLot G was manufactured using an 8QW:0 mixture of bauxite ore and nepheline svenite Prior to mixing with the nepheline syenite. the bauxite ore used n lot G had been calcined between 8004C and. latest 900C' in an industrial calciner. Boththhe over ealilned ore and nepheline syenite were separately milled to attain a dt particle size of approximately 8 pm before the ore and nepheline syenite were mixed with the 10 weight percent after and I weight percent PVA. Using the compaction pross described above, 6.5 g quantities of the mixture from lot ( were made into discs, -13- The discs froi lots F and G were heated to 1 250'T for two hours, The XRD and XRF analytical techniques used to characterize Lots D andE were used to characterize Lots F and G. The results are shown inl Tablei3 Table ot F I Lot G XRP j 0 824 17 XRD 44% corundum 49%corundum raio of the weight percerntof A1 2 0 3 to the total of AbCo and SiO The data supports tie conclusion that Lot G, which included the addition of nepheine syenite relative to Lot F, had a 0MI7 ratio of the weight percent of Alat 3 to Al.
3 and Si hch was lower than0.24 ratio ofthe weight percent of Ab03 to.Al 2 0 3 and SiO found in Lot .At the same tine, Lot G had 49 percent corundum which was higher than the 44 percent corundum in Lot F. For convenience, the data fion Tables 2 and 3 has been assembled below in Table 4 Table 4 L Lt E Lot F Lot G XRF 0.771 0.658 0 .824 0VI3 \RD ( corundum) 24 z 38 44 49 - --- ---- --- - ---- ----- --- .... tiao of theweight peeet of AJ0o to A1Q and SiC Lots D and F represent ceramic articles wherein the ratio of the weight percent of AbC; to Ai 2 C, and SiC 2 exceeds 0.72 and according to the A0 and i10 phase diagram, the presence of alunmina in crystalline phases (i e. corundum)vwould be expected .in contrast. lots E and G represent ceramic articles wherein the ratio of the weight percent of Ab0 3 to A1 2 0 3 and SiC 2 was less than 0.72 and the presence of alumina in crystaline phases would not be expected. Surprisingly, ceramic articles of embodiments of this invention include both a chemical composition wherein the ratio of the weight percent of Ab0 3 to Al3OC and SiCO is less than 0.2 and an alumina crystalline phase is present. Vthout wishing to be bound by a particular theory, it is believed that embodiments of the present invention allow 144relatively strong ceramic precmrsors to be created without reaching anquilibrum state where alpha aumina content it compromised. The combined impact of using nepheline syenite and overcalcined ore is evident in the data for lot ; which, according to XRD data, had an alumina crystaline phase content (ie. 49%) that was twice the amount of alumina crystalline phase found in Lot D (i.e24%) which did not incorporate either nepheline syenite or over calcined ore The above description is considered that of particular embodiments only. Modifications of the invention wil occur to those ski led in the art and to those vho make or use the invention. Therefore, it is understood that the embodiments shown in the drawings and described above are merely fOr ilustrative purposes and are not intended to limit the scope of the invention, which is defined by the flowing claims as interpreted according to the principles of patent law. A reference herein to a patent document or other matter whichis given as prior art is not taken as an admission that that document or prior art was pait of coinion general knowledge at the priority date of any of the claims. With reference to the use of the uord(s) comprise" or "comprises" or "comprising" in the foregoing description and/or in the follow g claims, unless the context requires otherwise, those words are used on the basis and clear understanding that they are to be interpreted inclusively, rather than exclusiely, and that each of those words is to be so terpreted in construg the foregoing description and/or the following claims. -15-